Houdini 20.5 Nodes LOP nodes

Render Settings

Creates or edits a UsdRenderSettings prim, which holds the general settings for rendering the scene.

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Since 18.0

Overview

  • A UsdRenderSettings prim holds global render settings for rendering the scene, as well as a list of UsdRenderProduct prims representing the rendered files/buffers, and which purposes should be rendered.

  • Render settings prims must be somewhere under /Render in the scene graph tree.

Creating vs. editing prims

This node belongs to a class of nodes that create or edit USD prims directly. These nodes operate in Create mode or Edit mode. This is controlled by a Create primitives checkbox or a Create/Edit popup menu. In create mode, the node creates new prims. In edit mode, the node changes the attributes on an existing prim. The Edit mode has two variations. Edit will not modify primitives which have a houdini:editable attribute set to false. Force edit will modify a primitive regardless of the existence or value of this attribute. This attribute can be set on a primitive using the Configure Primitives LOP.

Parameters that correspond to a USD attribute have a pop-up menu to the left that controls how the node authors the attribute.

In addition to that, any connectable USD attributes (i.e., the ones in the inputs: namespace) will have menu items that allow disconnecting them from their sources.

Pop-up menu item

Meaning

Set or Create

Sets the attribute to the given value, whether it previously existed or not.

Set If Exists

Only set the attribute to the given value if it previously existed.

Use this mode to make sure an attribute is only set on primitives of the correct type. For example, only UsdGeomSphere primitives are likely to have a radius attribute.

Block

Makes the attribute appear to not exist, so it takes on its default value. (If the attribute doesn’t already exist on the prim, this does nothing.)

Disconnect Input

Deletes the attribute input connection to its source. Input connections take precedence over attribute values, so disconnecting an input allows the attribute value to take effect.

Do Nothing

Ignore this parameter, don’t create or change the attribute in any way.

Parameters

Sampling Behavior

Cooking this node can generate many USD time samples, rather than just a single time sample at the current time. This can be equivalent to having a Cache LOP following this node, but it will evaluate much faster, and does not cache data from any other nodes. This allows animated data to be authored to USD without introducing a node time dependency which would then cause all following nodes to also be time dependent. This can vastly improve playback performance of some LOP Networks.

In all sampling modes, if a parameter on this node does not vary with time, and does not rely on other time sampled data from the stage, only a single default value will be generated in USD for the corresponding attribute. USD time samples are only generated for parameters that may vary over time.

Sample Current Frame

A single time sample will be generated for the current time.

Sample Frame Range If Input Is Not Time Dependent

If the input to this node is time dependent, this node behaves as if it is in Sample current frame mode. Otherwise it behaves as if it is in Sample frame range mode.

Sample Frame Range

The Start/End/Inc parameter is used to generate multiple times at which this node’s parameters are evaluated, and a USD time sample is created for each attribute at each one of these times.

Start/End/Inc

When the Sampling behavior is Sample frame range, this parameter controls the number and spacing of base time samples to be generated by this node. The default values of this parameter are @fstart, @fend, and @finc. These values correspond to the start, end, and step size of the global Houdini animation settings when interacting with Houdini. When using a ROP node to generate a range of frames, these values correspond to the start, end, and increment values specified on the ROP node being executed. This default ensures that a USD file written to disk will contain time samples for exactly the frame range requested by the ROP (regardless of the Houdini animation settings).

Subframe Sampling

For each primary sample generated by this node, these parameters can cause additional samples to be generated around that primary sample time. This is most often used to ensure that accurate data exists at exactly the camera shutter open and close times, as well as at the primary sample time.

Shutter

Controls the method used to specify the shutter open and close times relative to the primary sample times.

Specify Manually

The Shutter Open/Close parameter values provide exact offset values relative to the primary sample time.

Use Camera Prim

The Camera Prim parameter provides the scene graph path of a camera primitive from which the shutter open and close times are extracted to provide the offset values relative to the primary time sample.

Shutter Open/Close

When Shutter is set to Specify Manually, these two offset values are added to the primary sample time to indicate the shutter open and close times. The open time should be less than or equal to zero, and the close time should be greater than or equal to zero.

Camera Prim

When Shutter is set to Use Camera Prim, this is the scene graph path of a camera prim on the input node’s stage. The shutter open and close attribute values are read from this primitive.

Samples

The number of subframe samples to create for each primary sample. These samples are evenly distributed between the shutter open and close times. Note that such an even distribution may or may not create a sample at exactly the primary sample time.

Always Include Frame Sample

When turned on, forces a sample to be created at exactly the primary sample time. If the Samples value, together with the shutter open and close times, already place a sample at the primary sample time, turning on this option has no effect. Otherwise, this option causes an addition sample to be added. This means that the actual number of samples per primary sample may in fact be one more than the number specified in the Samples parameter.

Action

Whether this node should create new prims, or edit existing prims. In addition, the Force Edit option can be chosen to cause this node to ignore the houdini:editable attribute on prims, and always edit the specified attributes. This is in contrast to the Edit mode which will trigger a warning and not set attributes on prims with the houdini:editable attribute set to false.

Primitive Path

In create mode, this lets you control where in the scene graph to create the prim(s).

The default is usually /$OS. This creates a primitive at the root level with the same name as the node (for example, /tube1). This is a useful default for preventing naming conflicts, but terrible for organization. You should try to remember to change the Primitive path to a better value when you create prims.

For example, instead of naming models after the node that created them, you might want to name them after the geometry inside, and organize them under a /Models branch.

The “Create primitives” section contains basic controls for how to create the new prim(s).

Primitives

In edit mode, the node has a Primitive pattern parameter. This lets you specify the prim(s) the node should operate on. You can click the select button beside the text box to select the primitives from the scene graph tree. You can also use primitive patterns for advanced matching, including matching all prims in a collection.

Initialize Parameters

Changes the state of all control menu parameters to Do Nothing, so that this node will not apply any changes. Also grabs the current values of each property from the first Primitives match, and sets the values of the corresponding parameters to match. This means that changing any parameter’s control menu to Set or Create mode will set the property to its current value, making it easier to apply changes to an existing value rather than setting a brand new value.

Create Primitives

This section only appears when the node is creating primitives.

For example:

  • If you want to create a new cube primitive at /world/objects/cube1 on an empty stage: Set Primitive Specifier to “Define”, and the Parent Primitive Type to “Xform”.

  • If you want to override the radius of a sphere at /world/objects/sphere1: Set Primitive Specifier to “Over”, and the Parent Primitive Type to None. This makes sure the primitive types of any existing ancestor prims are not be modified by this node.

Primitive Count

The number of primitives to create.

Primitive Kind

Set all created prims to have this kind.

Primitive Specifier

The USD operator to use when creating the new prims.

Define

Authors a completely new prim. Use this if you want to create a brand new prim or replace an existing prim.

Over

Authors an override of an existing prim. Attributes not explicitly authored on this prim will get their values from the existing prim on the lower layer.

Class

Define a primitive class. This is usually not necessary unless you are doing deep USD magic.

Class Ancestor

If the Specifier is Define or Over, this parameter will cause some ancestor primitives to be authored with a specifier of Class. This makes it easy to create an Over or Define within a Class without having to use two separate nodes. When the Specifier is Class, this parameter is disabled because the entire primitive hierarchy is already authored as Class primitives.

Parent Primitive Type

If any parents of a path in Primitive paths do not exist, this node will automatically create them. In this case, it will create parent nodes of this type.

Standard

Products

A list of paths to UsdRenderProduct prims, representing the rendered outputs. If you don’t specify any explicit products, the renderer should by default output an RGB image using the render settings on this node, to a default display or image name.

Included Purposes

A list of purpose tokens (such as render (final render), proxy, and guide, from UsdGeomImageable). Only geometry with its purpose set to one of these tokens will be sent to the renderer. The default purpose is the purpose for all geometry that doesn’t have an explicitly set purpose, so you will usually want to include it.

(This cannot be specified per-product because it is a statement of which geometry is present.)

Material Binding Purposes

A list of material purpose tokens to consider when resolving material bindings.

Camera

Path to a USD camera (UsdGeomCamera) prim to render the scene from.

Resolution Mode

Use the USD Camera’s aperture aspect ratio to automatically set one dimension of the resolution.

The computed parm is set using an expression, but is locked to prevent accidental edits.

Manual

Set the resolution height and width values.

Set Width, Compute Height from Aperture

Set the width size, while height is computed from the width and the camera aspect ratio.

Set Height, Compute Width from Aperture

Set the height size, while width is computed from the width and the camera aspect ratio.

Resolution

The horizontal and vertical size of the output image, in pixels.

Disable Motion Blur

Override the camera’s Shutter close parameter to be equal to its Shutter open time, to produce a zero-width shutter interval. This is a convenient way to disable motion blur.

Aspect Ratio Conform Policy

What to do if the aspect ratio of the output image (Resolution width divided by height) doesn’t match the aspect ratio of the camera aperture (controlled by attributes on the camera). This allows a standard renderer to do something reasonable when you switch between cameras.

Expand Aperture

If necessary, expand the camera aperture to match the image.

Crop Aperture

If necessary, crop the camera aperture to match the image.

Adjust Aperture Width

If necessary, change the camera aperture width to match the image.

Adjust Aperture Height

If necessary, change the camera aperture height to match the image.

Adjust Pixel Aspect Ratio

Change the aspect ratio of the image to match the camera.

Data Window NDC

Directs the renderer to only render within this window of the entire output image. You specify the window as minX, minY, maxX, maxY, where each number is a normalized value from 0 to 1. 0, 0 is the bottom left, 1, 1 is the top right, 0.5, 0.5 is the center, and so on. The default is 0, 0, 1, 1 (no cropping). Note that you can use negative values. For example, -0.1, -0.1, 1.1, 1.1 will give you 10% overscan on each side.

You can use this window to temporarily crop the render to a smaller region, for testing purposes.

Pixels are only rendered if they are fully inside the window.

The normalized coordinates map to the image after any adjustments by the Aspect ratio conform policy.

Pixel Aspect Ratio

The aspect ratio (width/height) of image pixels (not the image itself). The default is 1.0, indicating square pixels.

Karma

Global

Rendering

Engine Settings

Select the UI for the specified rendering engine.

CPU

Shows the parameters for Karma CPU

XPU

Shows the parameters for Karma XPU

Image Mode

Determines how the image will be rendered.

progressive

The entire image will be progressively rendered, so the whole image resolves at the same time. This mode gives you a sense of what the whole image will look like without waiting for the render to complete.

bucket

Each bucket renders to completion before advancing to the next bucket. This mode lets you see what the final quality will be like without waiting for the whole image to render.

Note: When rendering for IPR, Karma will use progressive rendering until the IPR preview passes are complete.

Progressive Passes

When rendering in bucket mode (see imagemode), this is the number of progressive passes over the image to perform before switching to bucket mode.

Bucket Size

Karma breaks down an image into multiple buckets for rendering. This is the side length (in pixels) of the square bucket. The default is 32, specifying a 32 pixel x 32 pixel bucket. Threads operate at the bucket level, so it might be useful to lower the bucket size if there are only a few buckets that are particularly expensive. That way the expensive areas can be divided across more threads.

For example, if the image is mostly empty, but there’s a distant object that fits within single 32 x 32 bucket, then that object will only be rendered using 1 thread. If you switch to a 16 x 16 bucket, then the object might be split across 4 buckets and have 4 threads working on it.

Ideally changing the bucket size doesn’t change the results, but Karma measures variance across pixels within the current bucket, so if you set it to a low value, for example 4, Karma only has 4 x 4 = 16 pixels to look at, so Karma will tend to make very poor variance estimates. This can show up as black pixels, where pixel rendering terminated prematurely due to a bad variance estimate.

Bucket Order

Specifies which buckets are rendered first. Values can be:

middle

Buckets start from the middle of the image.

top

Buckets at the top of the image are rendered first.

bottom

Buckets at the bottom of the image are rendered first.

left

Buckets at the left side of the image are rendered first.

Note: When rendering to mplay, the user can click to focus on an area to render.

Sampling

Pixel Samples

The number of ray-samples sent through each pixel. More samples will result in a less noisy image. Also known as “Primary Samples”.

Path Traced Samples

The number of ray-samples sent through each pixel when using the path traced convergence mode. More samples will result in a less noisy image.

Image Blur

If you turn this off, Karma still calculates velocities, but sends all camera rays at shutter open, so the image will not have any apparent motion blur. This may be useful if you simply don’t want any motion blur. For example, if you want to add motion blur in post/compositing, but you still need the renderer to be aware of motion blur so that it saves out the proper motion vectors to an AOV.

Screendoor Limit

The number of transparent samples to be shaded as a ray travels through partially opaque objects. Increasing this value will result in less noise in partially opaque objects and is generally less costly than increasing Pixel samples, Volume Step Rate, or Min and Max ray samples. This parameter will not have any effect on noise from Indirect Sources however.

Convergence Mode

When set to Path Traced, maximum of 1 indirect ray is generated per bounce. When set to Automatic, the number of indirect rays is calculated based on initial noise estimate, target noise threshold, and the maximum number of camera rays. Also note that under Automatic mode, number of samples for direct lighting is adjusted based on noise estimate as well.

Russian Roulette Cutoff Depth

Depth at which indirect rays start to get stochastically pruned based on ray throughput.

Light Sampling Mode

Whether Karma should perform uniform sampling of lights or whether rendering should use the light tree. The light tree can be significantly faster for scenes that have large numbers of lights.

Some lights cannot be added to the light tree, and will all be sampled by Karma:

  • Dome Lights

  • Distant Lights

  • Point Lights

  • Lights with Light Filters

  • Lights with shaping controls (i.e. spot lights)

Light Sampling Quality

This is a global control to improve sampling quality for all lights. This acts as a multiplier on the individual light quality controls. Increasing the quality will improve direct light sampling as well as shadows/occlusion.

Indirect Guiding

Enable Indirect Guiding

When eabled, Karma collects radiance information on every shading point during the render and uses it to guide indirect bounce rays, rather than just relying on the BSDF sampling distribution. This can improve “difficult” lighting (for example, caustics, and mostly indirect lighting) but does add a bit of overhead. Before using this, you can try rendering direct and indirect AOVs to see where the noise is. If the noise is mostly caused by the direct lighting, there may be very little benefit.

Indirect Training Samples

The number of primary samples that karma will collect radiance information from. When set to 0, karma will collect information and refine guiding field throughout the entire render. If greater than zero, it will only do that until the specified number of samples and the remaining samples will be rendered using the guiding field but without refining it any further.

Indirect Guiding Spatial Filter

Applies blur to spatial component of path guiding samples while training. Can be increased to reduce grid-like artifacts at the cost of efficiency. Deprecated in 20.0.

Indirect Guiding Directional Filter

Applies blur to directional component of path guiding samples while training. Can be increased to reduce grid-like artifacts at the cost of efficiency. Deprecated in 20.0.

Indirect Guiding Deterministic

Attempts to produce deterministic result at increased render cost. Note that full determinism isn’t possible with multi-threaded renders since there may be tiny variations on geometry between runs (applies to any multi-threaded geometry processing such as precomputing normals, displacement, subdivision). This normally does not affect non-guided renders, but can cause butterfly effect with indirect guiding since the smallest variation may affect how the guiding field is built, which causes indirect rays to go in different directions, which leads to even more variation in the next iteration, and so on.

Indirect Guiding Components

List of BSDF components that use guiding for sampling when indirect guiding is enabled.

Indirect Guiding Render From Scratch Post-Training

Clears AOVs when training is completed for indirect guiding so that the pixel values accumulated during the training phase don’t contribute to the final render.

Shading

Ray Bias

The minimum distance used when testing if secondary rays from a surface intersect with other objects in the scene. The distance is measure from surface along the direction of the ray. Objects within the ray bias distance are ignored.

Automatic Ray Bias

Automatically compute ideal ray bias. Under Karma CPU, automatic bias applies to everything except procedural mesh and continued rays for partially opaque surfaces and nested dielectrics (the “Ray Bias” property is still used for those cases). Under Karma XPU, automatic bias applies to polymesh path bounce and polymesh shadow rays only. For everything else (eg SSS, rounded-edge, nested dielectrics, points, curves etc…) the “Ray Bias” property is still used.

Constrain by Maximum Roughness

Roughness parameter in GGX BSDFs are clamped by the maximum roughness value propagated down the ray chain in pathtracing. Enabling this option can cut out a lot of noise in indirect specular (in particular, cases where glossy surface is reflected by a rough specular surface) at the cost of a bit of accuracy.

Color Limit

The maximum value a shading sample is allowed to contribute to an LPE image plane to reduce appearance of “fireflies” caused by undersampling of extremely bright light sources. Note that reducing this value can result in an overall reduction in the amount of light in your scene.

Shared Color Limit

When enabled, indirect bounces use Color Limit value and Indirect Color Limit parameter is ignored.

Indirect Color Limit

Color limit applied to indirect bounce only. Note that this parameter is ignored unless Shared Color Limit toggle is disabled.

Enable Depth of Field

Enable depth of field rendering.

Automatic Headlight Creation

If there are no lights in the scene, a headlight is created by default. To disable, turn off this checkbox. Note that this parameter is deprecated in favor of Headlight Mode in USD Render ROP or --headlight commandline argument in husk.

Ambient Occlusion

Disable Lighting

Disable all lighting and material evaluation, using only the display color to shade primitives.

Override Lighting

Override lighting in the scene. There are several options:

  • Off: Use the lighting as defined on the USD stage

  • Emissive Objects: Disable all light sources so that only emissive objects (geometry lights) are enabled.

  • Headlight: Disable all light sources and create a headlight

  • Dome Light: Disable all light sources and create a dome light

Headlight AO Samples

When rendering in headlight mode, perform this many ambient occlusion samples per shade.

Headlight AO Distance

When rendering in headlight mode with ambient occlusion shading, this distance is used for occlusion testing. Smaller values will result in faster, but less accurate shading.

Headlight Fog Color

The color of the depthcue fog for disabled lighting.

Headlight Fog Alpha

The alpha for depthcue fog when lighting is disabled.

Headlight Fog Distance

The near/far distance for depth cue fog when lighting is disabled. If the far distance is less than the near distance, fog will be disabled.

Dicing

Dicing Camera

Specifies a camera that is used for dicing complicated surfaces. This can provide consistent dicing of surfaces when the viewing camera is moving.

Offscreen Quality

This parameter controls the shading quality scale factor for geometry that is not directly visible to the camera. For geometry that is outside the field of view (ie. visible only to secondary rays), karma will smoothly reduce the shading quality based on the angle between the geometry and the edge of the viewing frustum. Smaller values can increase performance particularly in scenes where the camera is within the displacement bound of nearby geometry, where it permits the hidden primitives to be diced more coarsely than those that are directly visible.

Dicing Quality Scale

This parameter is a global multiplier for dicing quality of all objects.

Image

Image Filters

Image filters post-process the filtered pixels to produce the final image. This parameter takes a string containg a JSON-encoded list of filters and their arguments. Usually you don’t need to craft this value by hand, it’s computed by the Karma LOP from the values of filter-related parameters. See Karma filters for more information.

Pixel Filter

Specifies the distribution of samples over pixels. A box filter will distribute samples randomly over the interior of each individual pixel. A Gaussian filter will distribute samples in a disk around the pixel center, but with a Gaussian distribution (instead of a uniform distribution).

Pixel Filter Size

This is the size of the Pixel Filter. A Guassian filter with a filter size of 1.8 will be slightly less blurry than a Gaussian filter with a filter size of 2.0.

Sample Filter

Sample filters are used to modify samples before they are sent to pixel filters.

This parameter specifies a list of filters. These filters are specified as a JSON list.

Pixel Oracle

When rendering, a Pixel Oracle tells karma which pixels need additional sampling and which pixels are converged. This parameter tells karma which oracle to use.

uniform

Uniformly distribute rays to each pixel. Each pixel will always get the same number of ray-samples.

variance

Distribute rays based on variance in the rendered image.

Use Background

“Off” disables Background IPR Filter. “Auto” enables it only for IPR. “On” enables it for both IPR and off-line rendering.

Background IPR Filter

JSON list of image filters specifically for background image preview and slap-comp of shadows and other holdout elements.

Advanced

Cache Limit

Whether to use a fixed size cache (karma:global:cachesize) or whether to use a proportion of physical memory (karma:global:cacheratio)

Cache Memory Ratio

The proportion of physical memory Karma will use for its unified cache.

For example, with the default vm_cacheratio of 0.25 and 16 Gb of physical memory, Karma will use 4 Gb for its unified cache.

The unified cache stores dynamic, unloadable data used by the render including the following:

  • 2D .rat texture tiles

  • 3D .i3d texture tiles

  • 3D .pc point cloud pages (when not preloaded into memory)

Note: This value is only used for off-line rendering, not IPR.

Cache Size (MB)

An explicit memory limit for the unified shading cache. This is deprecated in favor of using the Cache Memory Ratio.

Note: This value is only used for off-line rendering, not IPR.

Override Object Settings

Normally, geometry settings specified in the render settings LOP provide default values for objects. Each object can override the value of the default.

This parameter specifies a pattern of object property names whose values will taken from the render settings, overriding any per-object settings. For example, setting the pattern to “diffuselimit” will override the diffuse limit for all objects with the value specified on the render settings LOP.

Random Seed

This is the random seed to use for the render.

Cancel Render on Missing Texture

Enabling this option will cause karma to stop the render with an error if it encounters a missing texture map.

Cancel Render on No Working GPU Devices

Enabling this option will cause karma to stop the render with an error if no working gpu devices are discovered.

Export Components

A whitespace-separated list of shading component names that will be computed for export. If you have defined new component labels in your materials, these can be added to the list so that they are exported for per-component export planes. If you are not using some components, remove them from the list to improve render efficiency.

PBR light exports assume that this list is complete - that is, all components created by shaders are listed. If there are unlisted components, light exports may be missing illumination from these components.

Diffuse Components

A space-separated list of component types that will behave like diffuse bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

Refract Components

A space-separated list of component types that will behave like refract bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

Volume Components

A space-separated list of component types that will behave like volume bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

SSS Components

A space-separated list of component types that will behave like subsurface scatter bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

IPR

IPR Inc Random

When rendering to the Solaris viewport, this causes each render to start with a new random seed.

IPR Downsample Factor

The initial bucket size for IPR rendering.

IPR Denoise Bucket Size

As buckets are rendered, the coarse bucket size decreases. This specifies the bucket size at which Karma runs the de-noising filter on the image.

IPR Reserve Threads

When rendering in IPR mode, reserve this number of threads for other Houdini tasks.

IPR Continuous Dicing

When rendering in IPR mode, this setting controls whether Karma will re-dice displacements and sub-division surface when the view transform changes. Continuous re-dicing of geometry can add significant time to start-up time for the render, but will provide more accurate results.

Texture Baking

Map Type

Type of texture baking to do. Can choose between UDIM and PTex texture baking.

Object ID

Object ID for the object that will be unwrapped for texture baking. Texture baking will look for the objects in the scene that have the corresponding object ID per type (low resolution, cage and high resolution) and assigns them accordingly. There should only be one object per type

Tile

Tile number that this scene will be texture baking. For UDIM texture baking this is the UDIM index (between 1001 and 9999). For PTEX texture baking, faces are laid out onto paginated grids ordered from largest to smallest area. The tile number refers to which page is being baked currently.

PTex Minimum Resolution

Minimum resolution of a single PTex face when doing PTex texture baking.

PTex Maximum Resolution

Maximum resolution of a single PTex face when doing PTex texture baking.

PTex Small Face Percent

Used with PTex relative scaling. Refers to how many quads should approximately have resolutions less than the minimum resolution in relative scaling. This value is only an estimate based on the approximate lengths/widths of each face.

PTex Relative Scaling

Used to enable relative scaling for PTex. Relative scaling attempts to adjust the resolution of the PTex faces rendered based on the size of the meshes and the Texture Baking Small Face Percent. Relative scaling will adjust the minimum resolution so that a percent of the faces have less resolution than this minimum. This percent is the Texture Baking Small Face Percent

PTex Scale

Used to adjust the scaling of PTex face resolutions when doing PTex baking.

Default Geometry Settings

Motion Blur

Enable Motion Blur

Whether to enable motion blur. Changing this in the display options will require a restart of the render.

Velocity Blur

This parameter lets you choose what type of geometry velocity blur to do on an object, if any. Separate from transform blur and deformation blur, you can render motion blur based on point movement, using attributes stored on the points that record change over time. You should use this type of blur if the number points in the geometry changes over time (for example, a particle simulation where points are born and die).

If your geometry changes topology frame-to-frame, Karma will not be able to interpolate the geometry to correctly calculate Motion Blur. In these cases, motion blur can use a velocities and/or accelerations attribute which is consistent even while the underlying geometry is changing. The surface of a fluid simulation is a good example of this. In this case, and other types of simulation data, the solvers will automatically create the velocity attribute.

Note

In Solaris, velocities, accelerations, and angularVelocities attributes are equivalent to v, accel, and w in SOPs, respectively.

No Velocity Blur

Do not render motion blur on this object, even if the renderer is set to allow motion blur.

Velocity Blur

To use velocity blur, you must compute and store point velocities in a point attribute velocities. The renderer uses this attribute, if it exists, to render velocity motion blur (assuming the renderer is set to allow motion blur). The velocities attribute may be created automatically by simulation nodes (such as particle DOPs), or you can compute and add it using the Point velocity SOP.

The velocities attribute value is measured in Houdini units per second.

Acceleration Blur

To use acceleration blur, you must compute and store point acceleration in a point attribute accelerations. The renderer uses this attribute, if it exists, to render multi-segment acceleration motion blur (assuming the renderer is set to allow motion blur). The accel attribute may be created automatically by simulation nodes, or you can compute and add it using the Point velocity SOP.

When Acceleration Blur is on, if the geometry has a angular velocity attribute (w), rapid rotation will also be blurred. This should be a vector attribute, where the components represent rotation speeds in radians per second around X, Y, and Z.

When this is set to “Velocity Blur” or “Acceleration Blur”, deformation blur is not applied to the object. When this is set to “Acceleration Blur”, use the karma:object:geosamples property to set the number of acceleration samples.

Velocity motion blur used the velocity attribute (velocities) to do linear motion blur.
Acceleration motion blur uses the change in velocity to more accurately blur objects turning at high speed.
Angular acceleration blur works with object spin, such as these fast-spinning cubes.

Motion Samples from Stage

Instead of choosing the motion samples explicitly, Karma can also choose the motion samples based on the samples authored on the Usd stage. This option will choose just the right number of samples to capture the motion described on the stage.

This setting applies to both transform and deformation motion samples for both geometry and instances.

Note: If the samples on the stage don’t align with the shutter times on the camera, it’s possible there will be some minor interpolation issues over the first and last segments (since motion will be truncated rather than interpolated).

Geometry Time Samples

The number of sub-frame samples to compute when rendering deformation motion blur over the shutter open time. The default is 1 (sample only at the start of the shutter time), giving no deformation blur by default. If you want rapidly deforming geometry to blur properly, you must increase this value to 2 or more. Note that this value is limited by the number of sub-samples available in the USD file being rendered. An exception to this is the USD Skel deformer which allows.

“Deformation” may refer to simple transformations at the Geometry (SOP) level, or actual surface deformation, such as a character or object which changes shape rapidly over the course of a frame.

Objects whose deformations are quite complex within a single frame will require a higher number of Geo Time Samples.

Deformation blur also lets you blur attribute change over the shutter time. For example, if point colors are changing rapidly as the object moves, you can blur the Cd attribute.

Increasing the number of Geo Time Samples can have an impact on the amount of memory Karma uses. For each additional Sample, Karma must retain a copy of the geometry in memory while it samples across the shutter time. When optimizing your renders, it is a good idea to find the minimum number of Geo Time Samples necessary to create a smooth motion trail.

Deformation blur is ignored for objects that have Velocity motion blur turned on.

Transform Time Samples

The number of samples to compute when rendering transformation motion blur over the shutter open time. The default is 2 samples (at the start and end of the shutter time), giving one blurred segment.

If you have object moving and changing direction extremely quickly, you might want to increase the number of samples to capture the sub-frame direction changes.

In the above example, it requires 40 transformation samples to correctly render the complex motion that occurs within one frame. (This amount of change within a single frame is very unusual and only used as a demonstration.)

Transformation blur simulates blur by interpolating each object’s transformation between frames, so it’s cheap to compute but does not capture surface deformation. To enable blurring deforming geometry, increase karma:object:geosamples.

Instance Velocity Blur

When defining motion blur on instances, the transform of each instance can be blurred in addition to any motion blur occurring on the prototype. This option controls how the instance will compute the motion blur of the transform on each instance. For example, when instancing prototypes to a particle system, you'd likely want to use velocity blur to compute motion blur (the transform on the prototype would be blurred by the velocity on the particles).

No Velocity Blur

Use deformation blur of the instance to compute the blur on the transform.

Velocity Blur

To use velocity blur, the instance must be a point instancer with velocity attributes on the points.

The velocities attribute value is measured in Houdini units per second.

Acceleration Blur

To use acceleration blur, the instance must be a point instancer with point velocities and acceleration values. The renderer uses this attribute, if it exists, to render multi-segment acceleration motion blur (assuming the renderer is set to allow motion blur). The accel attribute may be created automatically by simulation nodes, or you can compute and add it using the Point Velocity SOP; this will be converted to accelerations when the SOP geometry is converted to USD.

Instance Motion Samples

When motion blur on instances is computed using Acceleration Blur or Deformation Blur, this parameter specifies the number of motion segments used for motion blur.

Motion Blur Style

Specifies the style of motion the object has.

Rotation Blur (default)

Rotates the object around the origin. This is ideal for objects that spin.

Linear Blur

This style of motion will not preserve the volume of rotating objects and will have linear motion instead of rotational arcs. Should only be used in special cases, i.e. with pivot transformations. Linear blur linearly interpolates the coefficients of the transformation matrix to achieve a correct blur.

Volume Velocity Blur Scale

Velocity multiplier used to reduce or exaggerate amount of motion blur on volumes.

Sampling

Diffuse Samples

Specifies the quality of indirect diffuse shading. A value of one translates to roughly one additional diffuse sample per shading computation. A sample of 4 translates to roughly 4 additional diffuse samples per shading computation.

Reflect Samples

Specifies the quality of indirect reflection shading. A value of one translates to roughly one additional reflection sample per shading computation. A sample of 4 translates to roughly 4 additional reflection samples per shading computation.

Refract Samples

Specifies the quality of indirect refraction shading. A value of one translates to roughly one additional refraction sample per shading computation. A sample of 4 translates to roughly 4 additional refraction samples per shading computation.

Volume Samples

Specifies the quality of indirect volumetric shading. A value of one translates to roughly one additional volumetric sample per shading computation. A sample of 4 translates to roughly 4 additional volumetric samples per shading computation.

SSS Samples

Specifies the quality of indirect sub-surface scattering shading. A value of one translates to roughly one additional sub-surface scattering sample per shading computation. A sample of 4 translates to roughly 4 additional sub-surface scattering samples per shading computation.

Volume Step Rate

How finely or coarsely a volume is sampled as a ray travels through it. Volumetric objects are made up of 3d structures called Voxels, the value of this parameter represents the number of voxels a ray will travel through before performing another sample.

The default value is 0.25, which means that every one of every four voxels will be sampled. A value of 1 would mean that all voxels are sampled and a value of 2 would mean that all voxels are sampled twice. This means that the volume step rate value behaves in a similar way to pixel samples, acting as a multiplier on the total number of samples for volumetric objects.

Keep in mind that increasing the volume step rate can dramatically increase render times, so it should only be adjusted when necessary. Also, while increasing the default from 0.25 can reduce volumetric noise, increasing the value beyond 1 will rarely see similar results.

Secondary Noise Level

Noise threshold to determine the number of indirect rays cast for indirect bounce when the Convergence Mode is set to “Automatic”. Decreasing this threshold (for example, to 0.001) will theoretically send more indirect rays and decrease noise, however the “extra” rays will likely be cancelled out by the Max Ray Samples parameter. The correct way to decrease noise is to increase the number of samples per pixel, rather than change this threshold.

If you are using Variance Pixel Oracle, you should set the same value for both threshold parameters. Setting the oracle’s threshold lower may make the indirect component reach its threshold sooner and cast fewer indirect rays, but the oracle decides to cast more expensive camera rays because the amount of final noise in the beauty pass is higher than the oracle’s threshold.

Min Secondary Samples

Minimum number of rays to cast in per-component variance anti-aliasing.

Max Secondary Samples

Maximum number of rays to cast in per-component variance anti-aliasing.

Limits

Diffuse Limit

The number of times diffuse rays can propagate through your scene.

Unlike the Reflect and Refract Limits, this parameter will increase the overall amount of light in your scene and contribute to the majority of global illumination. With this parameter set above zero diffuse surfaces will accumulate light from other objects in addition to direct light sources.

Diffuse Limit 0
Diffuse Limit 1
Diffuse Limit 2

In this example, increasing the Diffuse Limit has a dramatic effect on the appearance of the final image. To replicate realistic lighting conditions, it is often necessary to increase the Diffuse Limit. However, since the amount of light contribution usually decreases with each diffuse bounce, increasing the Diffuse Limit beyond 4 does little to improve the visual fidelity of a scene. Additionally, increasing the Diffuse Limit can dramatically increase noise levels and render times.

This is a float because all limits are stochastically picked per-sample, so for example you can set the diffuse limit to 3.25 and have 25% of the rays with a diffuse limit of 4 and 75% of rays with a diffuse limit of 3.

Reflection Limit

The number of times a ray can be reflected in your scene.

This example shows a classic “Hall of Mirrors” scenario with the subject placed between two mirrors.

This effectively creates an infinite series of reflections.

Remember that the first time a light source is reflected in an object, it is considered a direct reflection. Therefore, even with Reflect Limit set to 0, you will still see specular reflections of light sources.

Reflection Limit 0
Reflection Limit 1
Reflection Limit 2

From this camera angle the reflection limits are very obvious and have a large impact on the accuracy of the final image. However, in most cases the reflection limit will be more subtle, allowing you to reduce the number of reflections in your scene and optimize the time it takes to render them.

This is a float because all limits are stochastically picked per-sample, so for example you can set the diffuse limit to 3.25 and have 25% of the rays with a diffuse limit of 4 and 75% of rays with a diffuse limit of 3.

Refraction Limit

This parameter control the number of times a ray be refracted in your scene.

This example shows a simple scene with ten grids all in a row.

By applying a refractive shader, we will be able see through the grids to an image of a sunset in the background.

From this camera angle, in order for the image to be accurate, the refraction limit must match the number of grids that that are in the scene. However, most scenes will not have this number of refractive objects all in a row and so it is possible to reduce the refract limit without affecting the final image while also reducing the time it takes to render them.

Keep in mind that this Refract Limit refers to the number of surfaces that the ray must travel through, not the number of objects.

Remember that the first time a light source is refracted through a surface, it is considered a direct refraction. Therefore, even with Refract Limit set to 0, you will see refractions of Light Sources. However, since most objects in your scene will have at least two surfaces between it and the light source, direct refractions are often not evident in your final render.

This is a float because all limits are stochastically picked per-sample, so for example you can set the diffuse limit to 3.25 and have 25% of the rays with a diffuse limit of 4 and 75% of rays with a diffuse limit of 3.

Volume Limit

The number of times a volumetric ray can propagate through a scene. It functions in a similar fashion to the Diffuse Limit parameter.

Increasing the Volume Limit parameter will result in much more realistic volumetric effects. This is especially noticeable in situations where only part of a volume is receiving direct lighting. Also, in order for a volumetric object to receive indirect light from other objects, the Volume Limit parameter must be set above 0.

With the Volume Limit set to values above zero, the fog volume takes on the characteristic light scattering you would expect from light traveling through a volume. However, as with the Diffuse Limit, the light contribution generally decreases with each bounced ray and therefore using values above 4 does not necessarily result in a noticeably more realistic image.

Also, increasing the value of this parameter can dramatically increase the amount of time spent rendering volumetric images.

This is a float because all limits are stochastically picked per-sample, so for example you can set the diffuse limit to 3.25 and have 25% of the rays with a diffuse limit of 4 and 75% of rays with a diffuse limit of 3.

SSS Limit

The number of times a SSS ray can propagate through a scene. It functions in a similar fashion to the Diffuse Limit parameter.

This is a float because all limits are stochastically picked per-sample, so for example you can set the diffuse limit to 3.25 and have 25% of the rays with a diffuse limit of 4 and 75% of rays with a diffuse limit of 3.

Volume

Uniform Volume

Whether to render this object as if it was a uniform-density volume. Using this property on surface geometry is more efficient than actually creating a volume object of uniform density, since the renderer can assume that the volume density is uniform and place samples more optimally. The surface normal of the surface is used to determine which side of the surface will render as a volume - the normal will point away from the interior. The surface need not be closed - if the surface is not closed, the volume will extend an infinite distance away from the surface. Non-closed surfaces may produce unexpected results near the edge of the surface, so try to keep the viewing camera away from the edges.

Uniform Volume Density

Determines how the samples are distributed when rendering a uniform volume (karma:object:volumeuniform is enabled). This parameter must match the density on the uniform volume shader in order to produce correct results. Note that this property is deprecated in 20.0.

Uniform Volume Samples

The number of samples to generate when rendering a uniform volume (karma:object:volumeuniform is enabled). The samples will be distributed so as to produce an equal image contribution if they were all equal in brightness. Note that this property has no effect when global Screendoor Limit is greater than 0, so for all practical purposes it is deprecated.

Volume Sampling Field

Specifies the volume field by name that will be used for empty space culling. By default karma will use the 'density' field if it exists. If you are rendering an emissive volume in which some parts of the volume have a 0 density but still need to be rendered, you should specify a different field using this parameter.

Volume Filter

Some volume primitives can use a filter during evaluation of volume channels. This specifies the filter. The default box filter is fast to evaluate and produces sharp renders for most smooth fluid simulations. If your voxel data contains aliasing (stairstepping along edges), you may need to use a larger filter width or smoother filter to produce acceptable results. For aliased volume data, gauss is a good filter with a filter width of 1.5.

  • point

  • box

  • gauss

  • bartlett

  • blackman

  • catrom

  • hanning

  • mitchell

Volume Filter Width

This specifies the filter width for the “Volume Filter” property. The filter width is specified in number of voxels. Larger filter widths take longer to render and produce blurrier renders, but may be necessary to combat aliasing in some kinds of voxel data.

Shading

Diffuse Quality

This parameter acts as a multiplier on Min Secondary Samples and Max Secondary Samples for indirect diffuse component.

Reflection Quality

This parameter acts as a multiplier on Min Secondary Samples and Max Secondary Samples for indirect reflect component.

Refraction Quality

This parameter acts as a multiplier on Min Secondary Samples and Max Secondary Samples for indirect refract component.

Volume Quality

This parameter acts as a multiplier on Min Secondary Samples and Max Secondary Samples for indirect volume component.

SSS Quality

This parameter acts as a multiplier on Min Secondary Samples and Max Secondary Samples for SSS component.

Cusp Angle

If there are no normals on an object, any edges with a dihedral angle greater than this value will be cusped. For compatibility with mantra, Karma will also look for a detail attribute named vm_cuspangle (which takes priority over the setting).

Holdout Mode

When this is set to “Matte” mode, the object will be considered to be a cutout matte. Any lighting contribution and alpha of the object will be redirected to LPE AOVs with “holdouts” prefix. Holdout Mode does not affect the utility AOVs such as ray:hitP and ray:hitN. “Background” mode is similar to “Matte”, except it’s used for background plate so it will appear “pre-lit” in indirect bounces, multiplied by shadow contribution. Diffuse albedo of the shader is used to determine the pre-lit irradiance.

Fix Shadow Terminator

Adjust shading position of shadow rays to avoid self-shadowing artifact on low-poly mesh due to discrepancy between smooth normals and face normals.

Bump Shadow Terminator

With strong bump or normal maps you often see an abrupt/hard shadow terminator line. This parameter is a threshold and you enter an angle in radians: for angles that are smaller than or equal to the entered value, you will get a soft shadow terminator. If the angle is greater than the threshold, a hard terminator appears. A value of 0 disables the feature and you’ll always see a hard shadow terminator. Bump Shadow Terminator preserves the shape of the highlights while softening the terminator.

LPE Tag

Custom label assigned to lights or objects for use with light path expression.

Direct Refraction Subset

For compound BSDFs with refractive components, only apply direct lighting for lights that belong in specified location. A light ray facing the same direction as geometry normal is considered “Outside”. For transparent material that are solid/closed-manifold, setting this parameter to “Outside” can improve render performance by reducing noise in direct lighting and cut down on wasted shadow rays.

Dielectric Priority

Specifies the priority of a refractive material, allowing the renderer to choose which of many overlapping refractive materials should take precedence while rendering. This enables effects like water in a glass with ice cubes. The default (highest priority) is 0, and as the number increases (1, 2, 3, etc.), the priority decreases.

Enable Caustics

Brute-force caustics from transmissive objects. Allows evaluation of glossy BSDF that’s seen by indirect diffuse bounce. Often requires a significantly higher number of diffuse rays to resolve, especially if Caustics Roughness Clamp parameter is set to very small value or Indirect Guiding feature is disabled.

Fake Caustics
True Caustics

Caustics Roughness Clamp

Forces a minimal roughness for true caustics, above what the shader has set. Increasing this value can make caustics less noisy at the cost of accuracy.

Caustics Roughness: 0
Caustics Roughness: 0.2 (default)
Caustics Roughness: 0.5
Caustics Roughness: 0.8

Note

Roughness clamp only works with GGX BSDF and may not have any effect with Phong, cone, or specular BSDFs.

Enable Internal Reflection

Lets you evaluate the internal reflection on the backface of a glossy transmissive BSDF. Turn on this option to apply internal reflections. Note that this option has no effect on MaterialX Standard Surfaces with Thin Walled turned on: these materials always show internal reflections.

Evaluate BSDF On Fake Caustics

Allows the BSDF to affect the fake caustics, meaning (eg) a red bottle will automatically cast red shadows. Disabling the BSDF can reduce render times, but means fakecausticscolor should be used instead to set a constant shadow color.

Fake Caustics Color

Tints the fake caustics. Use this to darken the result of the BDSF, or to set a constant shadow color if the BSDF is disabled.

Fake Caustics Opacity

Controls the opacity of fake caustics. Use this to lighten the result of the BDSF.

Light

Treat As Light Source

Any object with an emissive material will generate light within the scene. If an object is significant enough (eg size, brightness, etc…) then it is possible for Karma to treat that object as if it were an explicit lightsource (similar to regular lights), meaning the emitted light will be handled much more efficiently. But doing so will add extra overhead elsewhere in the system (eg increased memory usage, slower update times, etc…).

There are three options. “No” will set the object as not being a lightsource. “Yes” will set the object as being a lightsource. “Auto” (default) means Karma will use an internal heuristic to decide if the object should be treated as a lightsource.

Light Sampling Quality

When an object is used as a geometry light source, this sets the per-light sampling quality. Increasing the quality will add additional samples for this light source, improving the sampling quality of this light relative to other light sources.

Note: This is not the quality of light received by an object.

Light Source Diffuse Multiplier

A multiplier for the effect of this emissive object on the diffuse, SSS, and volume response of materials

Light Source Specular Multiplier

A multiplier for the effect of this emissive object on the reflection and refraction response of materials

Is Portal

When enabled, the object will turn into a “light portal” that only lets in certain portion of dome lights based on portal geometry visibility.

Portal Dome Lights

Space-separated list of dome lights to associate this portal with.

Geometry

Render Points As

When rendering point clouds, they can be rendered as camera oriented discs, spheres or discs oriented to the normal attribute.

Render Curves As

When rendering curves, they can be rendered as ribbons oriented to face the camera, rounded tubes or ribbons oriented to the normal attribute attached to the points.

Override Curves Basis

USD supports Curve Basis types that may not be supported directly in Houdini. In some cases, you may want to override the Houdini curve basis. For example, if you have linear curves in Houdini, you may want to render them with a Bezier, B-Spline or Catmull-Rom basis. This menu will force Karma to override the basis that’s tied to the USD primitives.

Note that the topology of the curves must match the target basis. For example, when selecting any cubic curve basis, every curves must have at least 4 vertices. For the Bezier basis, curves must have 4 + 3*N vertices.

Cull Backface

If enabled, geometry that are facing away from the camera are not rendered.

Orientation

May be queried via objectstate vex function and will be “rightHanded” or “leftHanded” depending on the geometry’s winding order. This property is derived from USD geometry’s orientation attribute and not directly settable.

Dicing

True Displacements

This setting controls how the displacement shader on the object will be run. Bump Mapped Displacement

The displacement shader is run, but only modifies the surface normal. This does not dice geometry and can save memory.

True Displacement

The geometry is diced and displaced. This will cause proper silhouettes and shadowing of displaced surfaces.

Disable Displacement Shader

Disable the displacement shader entirely. There will be no bump mapping or displaced geometry.

Dicing Quality

This parameter controls the geometric subdivision resolution for smooth surfaces (subdivision surfaces and displaced surfaces). With all other parameters at their defaults, a value of 1 means that approximately 1 micropolygon will be created per pixel. A higher value will generate smaller micropolygons meaning that more shading will occur - but the quality will be higher.

The effect of changing the shading quality is to increase or decrease the amount of shading by a factor of karma:object:dicingquality squared - so a shading quality of 2 will perform 4 times as much shading and a shading quality of 0.5 will perform 1/4 times as much shading.

Dicing Flatness

This property controls the tesselation levels for nearly flat primitives. By increasing the value, more primitives will be considered flat and will be sub-divided less. Turn this option down for more accurate (less optimized) nearly-flat surfaces.

Dicing Minimum Depth

When not set to -1, karma will set minimum number of rows and columns on each face to be 2 to the power of this value when dicing for subdivision or displacement.

Dicing Maximum Depth

When not set to -1, karma will set maximum number of rows and columns on each face to be 2 to the power of this value when dicing for subdivision or displacement. Setting the same (or lower) value as “Dicing Minimum Depth” is effectively equivalent to fixed parametric subdivision that ignores raster space/offscreen measurement. Recommended leaving this value at -1.

LOP nodes

  • Add Variant

    Adds one or more variants to a variant set on a primitive. This node creates the primitive if it doesn’t exist.

  • Additional Render Vars

    Create multiple render vars.

  • Asset Reference

    Reference, Transform, and select variants of a USD Asset.

  • Assign Material

    Assigns a material to one or more USD primitives. You can use also programmatically assign materials using VEX, programmatically override material settings for each assignment, and programmatically assign materials to geometry subsets.

  • Assign Prototypes

    Switch point instances or USD instanceable prims to instance a different prototype.

  • Attribute VOP

    Create/edit USD attribute values using a VOP network.

  • Attribute Wrangle

    Create/edit USD primitive attributes using a VEX snippet.

  • Auto Select LOD

    Automatically selects a level-of-detail variant based on the primitive’s distance from the camera.

  • Background Plate

    Sets up hold-out or matte objects that leave holes in the scene through which the background is visible. These prims still take shadows and contribute to reflections as if they were the background.

  • Bake Skinning

    Bakes animation driven by a UsdSkel into transforms and point positions.

  • Basis Curves

    Creates or edits a basis curves shape primitive.

  • Begin Context Options Block

    This node begins a block of LOP nodes, within which certain context options have certain values.

  • Blend

    Partially applies edits to a layer’s attributes based on a fractional weight.

  • Blend Constraint

    Blends transforms according to a list of weights specified as parameters.

  • Cache

    Caches the results of cooking the network at different times, increasing playback speed.

  • Camera

    Adds a USD camera to the scene.

  • Capsule

    Creates or edits a capsule (tube with hemispherical ends) shape primitive.

  • Collection

    Creates/edits collections using primitive patterns.

  • Component Geometry

    Geometry container or import source, in a network created by the Component Builder tool.

  • Component Geometry Variants

    Sets up geometry variants, in a network created by the Component Builder tool.

  • Component Material

    Assigns materials to geometry in a network created by the Component Builder tool.

  • Component Output

    Assembles the final Component prim, in a network created by the Component Builder tool.

  • Cone

    Creates or edits a cone shape primitive.

  • Configure Layer

    Edits metadata on a layer.

  • Configure Primitives

    Edits various metadata on one or more primitives.

  • Configure Properties

    Configures metadata on properties (relationships and attributes).

  • Configure Stage

    Configures metadata for how to load layers into the stage and asset resolution.

  • Coordinate System

    Define named coordinate systems used in shaders.

  • Copy Property

    Copy properties from one primitive to another, or renames properties on a primitive.

  • Create LOD

    Uses the PolyReduce SOP to automatically generate multiple levels of detail from a high-res model, and stores them as USD variants.

  • Cube

    Creates or edits a cube shape primitive.

  • Cylinder

    Creates or edits a cylinder shape primitive.

  • Distant Light

    Creates or edits a USD Distant Light, representing a far-off light source such as the sun. Adds some useful Karma-specific attributes.

  • Dome Light

    Creates or edits a USD Dome Light prim. A dome light emits light inward, simulating light coming from the sky/environment surrounding the scene.

  • Draw Mode

    Sets draw mode properties on USD model assets.

  • Drop

    Runs a simulation to drop primitives under gravity.

  • Duplicate

    Creates copies of a prim (and its descendants).

  • Edit

    Interactively transforms prims in the viewer. Can use physics collisions to position props realistically.

  • Edit Context Options

  • Edit Material

    Allows you to edit an existing USD material by modifying parameters and shader connections. This can be useful if the existing material is on a non-editable layer.

  • Edit Material Properties

    Lets you build a spare parameter interface that reflects material or shader input attributes to directly edit their values.

  • Edit Properties

    Lets you build a spare parameter interface to directly edit attribute and relationship values.

  • Edit Properties From Node

    Lets you refer to the parameter on another node to directly edit attribute and relationship values.

  • Edit Prototypes

    Modify the prototypes of native or point instances in-place, without disturbing the instancing setup.

  • Edit Target Layer

    Allows you to apply edits directly in a lower layer, instead of overriding prims and attributes in the active layer.

  • Error

    Generates a message, warning, or error, which can show up on a parent asset.

  • Explore Variants

    Visualize, set, or extract variants on primitives.

  • Extract Instances

    Converts (heroes) an instance into a real editable prim.

  • Fetch

    Grabs the output of another LOP, potentially in another LOP network.

  • File Cache

    Caches (writes out once and then reads from) USD layers (possibly animated) to disk.

  • Follow Path Constraint

    Constrains a prim to follow a path curve.

  • For Each

    The end node of a For-Each loop block.

  • Geometry Clip Sequence

  • Geometry Color

    Adds display color and display opacity primvars to geometry.

  • Geometry Sequence

    Imports a sequence of geometry files into LOPs as animated geometry.

  • Geometry Subset VOP

    Creates USD geometry subsets within geometry prims (similar to groups in SOPs) based on evaluating a VEXpression or VOP network.

  • Graft Branches

    Takes prims/branches from the second input and attaches them onto branches of the scene graph tree in the first input.

  • Graft Stages

    Takes scene graph trees from other inputs and attaches them onto branches of the scene graph tree in the first input.

  • HDA Dynamic Payload

    Cooks a OBJ or SOP asset on disk and imports the animated geometry output as a USD payload.

  • Hermite Curves

    Creates or edits a hermite curves shape primitive.

  • Houdini Feather Procedural

    Generates feathers for rendering.

  • Houdini Preview Procedurals

    Invokes Houdini Procedurals while working interactively.

  • Houdini Procedural: Crowd

    Houdini Crowd Procedural for Solaris.

  • Houdini Procedural: Hair

    Houdini Hair Procedural for Solaris.

  • Houdini Procedural: Ocean

    Houdini Ocean Procedural for Solaris.

  • Houdini Procedural: RBD

    Houdini RBD Procedural for Solaris.

  • Inline USD

    Parses usda code representing a layer and adds it to the layer stack.

  • Insertion Point

    Represents a point in the node graph where nodes can be inserted.

  • Instancer

    Instances or copies primitives onto points.

  • Isolate Scene

    Work in masked areas of the stage.

  • Karma

    Renders the USD scene using Houdini’s Karma renderer.

  • Karma Cryptomatte

    Setup Cryptomatte AOVs for Karma.

  • Karma Fog Box

    Creates a constant volume within a box.

  • Karma Physical Sky

    Creates a Karma Sky Dome and Sun Light rig.

  • Karma Render Products

    Create multiple render products sharing common settings.

  • Karma Render Properties

    Configure Render Properties for Karma.

  • Karma Sky Atmosphere

    Creates or edits a Karma Sky Atmosphere.

  • Karma Sky Dome Light

    Creates or edits a Karma Sky Dome Light.

  • Karma Standard Render Vars

    Create standard karma render vars (AOVs/Image Planes).

  • LPE Tag

    Manage Lights' LPE Tags.

  • Labs Karma AOVs for RenderMan Denoiser

    Generates AOVs for the Pixar RenderMan denoiser.

  • Layer Break

    Starts a new active sublayer that subsequent nodes will edit, and indicates all previous layers will be discarded when saving to disk.

  • Layer Replace

    Replaces all uses of a certain layer with a substitute layer from its second input.

  • Layout

    Provides tools for populating a scene with instanced USD assets. You can place individual components, paint/scatter components in different ways using customizable brushes, and edit existing instances.

  • Light

    Creates or edits a USD Light prim. This node also adds some useful Karma-specific attributes.

  • Light Filter Library

    Authors USD light filter primitives from VOP nodes.

  • Light Linker

    Creates USD light link properties based on rules.

  • Light Mixer

    Lets you interactively edit USD properties for multiple lights.

  • Load Layer for Editing

  • Loft Payload Info

    Adds basic information from inside a payload to the primitive that loads the payload.

  • Look At Constraint

    Constrains a prim to always point toward a target.

  • Mask from Bounds

    Sets a primvar based on whether/by how much selected prims are inside a bounding shape.

  • Match Size

    Resizes and recenters the input geometry to match a reference bounding box.

  • Material Library

    Authors USD material primitives from shader VOP nodes.

  • Material Linker

    Creates material assignments based on rules.

  • Material Variation

    Creates attributes/primvars to override material parameters per-prim/instance.

  • Merge LOP

    Merges the layers from incoming stages into a unified layer stack.

  • Merge Point Instancers

    Merges point instancers into a single consolidated point instancer.

  • Mesh

    Creates or edits a mesh shape primitive.

  • Modify Paths

    Modify asset path attribute values.

  • Modify Point Instances

    Modifies point transforms and property values for individual point instances.

  • Motion Blur

    Adds time samples to allow motion blur when rendering.

  • Null

    This node does nothing. It can be useful to insert a Null into a network as a fixed point in the network that you can refer to by name in expressions/scripts.

  • Output

    Represents the output of a subnetwork. Allows you to design a node asset with multiple outputs.

  • Parent Constraint

    Makes a primitive appear to inherit the transform hierarchy of another prim somewhere else in the tree.

  • Points

    Creates or edits a Points shape primitive.

  • Points Constraint

    Position and Orient primitives using point positions from a geometry.

  • Primitive

    Bulk-creates one or more attributes of a certain type.

  • Prune

    Hides or deactivates primitives and point instances.

  • Python Script

    Lets you write Python code in the node to use the USD API to directly manipulate the stage.

  • RBD Destruction

    An example for a fracturing simulation in USD, also useful as a canned effect.

  • Reference

    References the contents of a external USD files and/or layers created by other LOP nodes into a branch of the existing scene graph tree. Can also remove or replace existing references.

  • Render Geometry Settings

    Applies renderer-specific geometry settings to geometry in the scene graph.

  • Render Product

    Creates or edits a UsdRenderProduct prim, which represents an output of a renderer (such as a rendered image file or other file-like artifact produced by a renderer), with attributes configuring how to generate the product.

  • Render Settings

    Creates or edits a UsdRenderSettings prim, which holds the general settings for rendering the scene.

  • Render Var

    Specifies a custom variable computed by the renderer and/or shaders, either a shader output or a light path expression (LPE).

  • Resample Transforms

    Generates interpolated transform time samples from existing time samples on USD prims.

  • Restructure Scene Graph

    This node has various operations for editing prim paths, variant sets, and composition arcs.

  • Retime Instances

    Offsets and/or scales the timing of animation on selected instances.

  • SOP Character Import

    Imports a character or animation from a SOP network into the USD scene graph.

  • SOP Create

    Lets you create geometry in a SOP subnetwork inside this node, so you can create geometry in-place in the LOP network instead of needing a separate SOP network.

  • SOP Crowd Import

    Imports a crowd from a SOP network into the USD scene graph.

  • SOP Import

    Imports geometry from a SOP network into the USD scene graph.

  • SOP Modify

    Converts USD geometry into SOP geometry, runs the SOP subnet inside this node on the geometry, and converts the changes back to USD overrides.

  • Scene Doctor

    Validates primitives on a USD stage.

  • Scene Import

    Imports models, materials, and lights from the Object level into the LOP network.

  • Scope

    Creates a scope primitive. Scope is the simplest form of grouping, and does not have a transform. Scopes can be useful for organizing the scene tree.

  • Set Extents

    Sets the bounding box metadata of selected primitives.

  • Set Variant

    Selects (switches to) one of the variants stored in a variant set on a primitive.

  • Simulation Proxy

    Generates low-poly collison geometry suitable for physical simulation and creates a proxy relationship to the original model.

  • Sphere

    Creates or edits a sphere shape primitive.

  • Split Point Instancers

    Splits a point instancer into two or more instances, which divide up the original instances.

  • Split Primitive

    Splits USD geometry prims into child primitives based on geometry subsets or primvar values.

  • Split Scene

    This node splits a scene graph into two disjoint sets of primitives.

  • Stage Manager

    Provides a convenient interface to reference in many files at once and place them in the scene graph tree.

  • Store Parameter Values

    Lets you store temporary (unsaved) data in the stage.

  • Sublayer

    Imports from USD files or other LOP node chains into as sublayers, or removes/replaces/reorders existing sublayers.

  • Subnet

    Encapsulates a LOP subnetwork, allowing you to organize and hide parts of the network.

  • Surface Constraint

    Constrain a prim to stick to a surface.

  • Switch

    Passes through one of several inputs, based on a parameter choice or expression.

  • TimeShift

    Outputs the stage as it is at a different point in the timeline.

  • Transform

    Edits the transforms of selected USD primitives.

  • Transform UV

    Moves, rotates, and scales texture coordinates on USD primitives.

  • USD ROP

  • USD Render ROP

  • Unassign Material

    Unbinds a material from one or more USD primitives.

  • Value Clip

  • Vary Material Assignment

    Assign different materials across a number of prims to create variation.

  • Volume

    References volume data on disk into a volume prim containing field prims.

  • Xform

    Creates or edits an Xform prim. Xform (and its sub-classes) represents a transform in the scene tree.