Houdini 20.5 Nodes Geometry nodes

Rig Attribute VOP geometry node

Runs a VOP network to modify geometry attributes on a KineFX rig.

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Since 18.5

Overview

This node behaves in the same way as the Attribute VOP, except it has a Rig tab in its parameters. The Rig tab exposes a custom viewport state and parameters to automatically recompute the point transforms for the node’s inputs and output.

You can use this node to build a VOP network for your KineFX rig. To access the KineFX VOP nodes, double -click this node and build your VOP network inside. Alternatively, you can specify a SHOP node containing the VOP network or specify a .vfl file containing the CVEX program.

Note

KineFX VOP networks run in the CVEX context, not the SOP context. This means that SOP-specific VOPs and VEX operations are not available inside this node. Please use the From File variants and the provided operator input strings instead.

This node also modifies geometry attributes. To specify inputs, create Parameter VOPs with the names of attributes and then in those nodes' parameters turn on exporting (Export parameter set to Always or When Input is Connected) to allow the writing to or creation of the corresponding attributes.

Parameters

Group

Only run the VOP network on this group in the input geometry. Leave this parameter field blank to modify all the input geometry.

Group Type

What the group is made of.

Run Over

Apply the VEX code to each component of this type (points, primitives/faces, or vertices. Or choose Detail to run the code only once. For each component, the code runs with attributes bound to variables starting with @ (for example @Cd) for reading and writing.

If you choose Numbers, Houdini runs the code for certain number of iterations instead of over components. In this mode the code only has read-only detail-level attributes bound to @ variables.

Number Count

When Run Over is Numbers, the number of iterations to run the code. In each iteration, @numelem is bound to this total count, and @elemnum is bound to the iteration number, from 0 to @numelem - 1.

In this mode the code only has read-only detail-level attributes bound to @ variables.

Thread Job Size

When Run Over is Numbers, this is the number of iterations to run per separate thread. If this number is greater than or equal the Number count, all iterations will run serially in a single thread. If this is 1, each iteration will run in a separate thread. In between, the node will group the iterations into batches of this size, and run each batch in parallel on separate threads.

Vex Setup

VEX Source

Determines where to get the program to modify the attributes from.

Myself

Use a VOP network from inside this node.

SHOP

Use a SHOP node containing a CVEX VOP network. You can specify the node in the SHOP Path parameter field.

This can also point to any node that contains a CVEX VOP Network.

Note

Referenced nodes' parameters can be used.

Script

Use a file containing a CVEX program. You can specify the file path in the Script parameter field.

SHOP Path

Specifies the SHOP node that contains a CVEX VOP network.

This parameter is only available when VEX Source is set to SHOP.

Script

Specifies a path to a file containing a CVEX script.

This parameter is only available when VEX Source is set to Script.

Re-load VEX Functions

Reloads any .vex files to account for changes made outside of Houdini.

This parameter is only available when VEX Source is set to Script.

Compiler

Specifies the command line Houdini uses to compile the VOP network inside this node.

This parameter is only available when VEX Source is set to Myself.

Force Compile

Recompiles the VOP network inside this node.

This parameter is only available when VEX Source is set to Myself.

Evaluation Node Path

VEX functions like ch() usually evaluate with respect to this node. This parameter lets you specify a node path to override where the path search starts from. This is useful for embedding in a digital asset, where you want searches to start from the asset root.

Export Parameters

When a VEX parameter is exported, the bound attribute will be created if one doesn’t exist. This parameter lets you specify a pattern that can be used to override the export option on the VEX shader to avoid writing to or creating certain attributes. When the pattern matches the VEX parameter, not the bound attribute, the attribute will still be bound for reading.

Enable Multithreading

When on, in the unlikely event that there is a threading issues with VEX, this parameter will allow you to determine which node is guilty and work around it without having to turn off threading on a global scale.

Attribute Bindings

VEX Precision

Evaluates VEX at 32-bit or 64-bit precision. 64-bit provides higher accuracy, especially for transforms.

Use the Attribute Cast SOP to change the preferred precision.

Note

Incoming attributes will preserve their original precision, so using 64-bit VEX on 32-bit positions will convert them to 64-bit, apply the operation, then convert back to 32-bit when writing out.

Auto

Switches between 32-bit and 64-bit depending on the preferred precision of the incoming geometry.

32 Bit

Any created attributes will be 32-bit.

64 Bit (Experimental)

Any created attributes will be 64-bit.

Autobind by Name

When on, automatically binds attributes to parameters by name. If for some reason you need CVEX parameters to have different names than their corresponding attributes, turn off this parameter and use the Number of Bindings multiparm instead.

Number of Bindings

Multiparm that lets you set up mappings between Attribute Name and VEX Parameter. Integer attributes will bind to integer parameters. Float attributes will bind to float, vector, point, matrix, or matrix4 parameters depending on their tuple size. String attributes will bind to string parameters.

Attribute Name

Name of the attribute to bind to the specified VEX Parameter.

VEX Parameter

Name of the parameter to bind to the specified Attribute Name.

Autobind Groups by Name

When on, automatically binds any groups to the integer parameter prefixed with group_.

Group Bindings

Multiparm that lets you manually specify the bindings of each group by setting up the mappings between groups and parameters.

Group Name

Name of the group to bind to the specified VEX Parameter.

VEX Parameter

Name of the parameter to bind to the specified Group Name.

Update Normals If Displaced

If points are being run over and the P attribute is written to, but the N attribute is not written to, then any incoming normals will become out-of-date. When this parameter is on, vertex and point normals will be updated when this occurs.

Attribute to Match

The @opinput‹inputnum›_‹name› syntax lets you get the value of an attribute from the corresponding element on another input. If this parameter field is empty, then the corresponding element is the element with the same index (for example, point number) as the element the node is currently processing. If you specify the name of an attribute in this parameter field, then the corresponding element is the element that has the same value in the named attribute as the current element.

For example, if you use id as the Attribute to Match, and you process a point with attribute id set to 12, then @opinput1_P would give you the P attribute on the point in the second input that also has id set to 12.

See accessing attributes from other inputs on the VEX snippets page for more information.

Compute Results In Place

When on, the Rig Attribute VOP node is able to work on the incoming geometry in place without making a copy of it. This can speed up processing as one less copy is made, but requires that the VEX code doesn’t bind for writing any attributes that are read from the first input.

Output Selection Group

Specifies the name of a group to use as the output selection. When the highlight flag is enabled for the Rig Attribute VOP node, this group will be the output selection used by downstream modeling tools (if they exists).

Rig

Viewport State

Specifies a string pointing to a valid viewport state name.

Compute Transforms for Output

When on, computes the transforms for the output. Gives you the same behavior as adding a Compute Transform after the output.

Compute Transforms for Input 1

When on, computes the transforms for Input 1. Gives you the same behavior as adding a Compute Transform before the input.

Compute Transforms for Input 2

When on, computes the transforms for Input 2. Gives you the same behavior as adding a Compute Transform before the input.

Compute Transforms for Input 3

When on, computes the transforms for Input 3. Gives you the same behavior as adding a Compute Transform before the input.

Compute Transforms for Input 4

When on, computes the transforms for Input 4. Gives you the same behavior as adding a Compute Transform before the input.

Examples

CameraOnPath Example for Rig Attribute VOP geometry node

This example demonstrates how to use the KineFX Transform from Path, Blend Transforms, and Offset Transform VOPs in SOP to constrain a camera on a path.

CurveSolverVop Example for Rig Attribute VOP geometry node

This example demonstrates how to use the KineFX CurveSolver VOP in SOP. It does the same as the Follow Curve mode on the InverseKIN CHOP.

IkSolverVop Example for Rig Attribute VOP geometry node

This example demonstrates how to use the KineFX IkSolver VOP in SOP. It does the same as the Inverse Kinematics with Twist Affector mode on the InverseKIN CHOP.

See also

Geometry nodes