Solaris user interface

Guide to using the user interface to interact with LOP networks and USD data.

Houdini includes a Solaris desktop. This includes the scene graph tree pane and scene graph details pane, and limits the shelf tools to tools that currently work well with LOPs.

(Future versions of Houdini will expand the set of tools that work with LOPs.)
The scene graph tree pane displays the tree in the output of the selected LOP node.
The scene graph details pane displays the attribute values and metadata on the currently selected USD prim in the scene graph tree.
The scene graph layers pane shows the layer stack in the selected LOP node.
The network editor for LOPs is quite similar to SOPs in Houdini, with some extra features.
- You can display non-contributing nodes in the bypassed style. This is off by default).
- You can display an outline around nodes. Groups of nodes with different colors are writing into different active layers. (This lets you see if/when a node starts a new layer, since its outline has a different color from the node above.) This is on by default.
You can change these settings in the network editor’s View menu.
The clone control pane provides a way to create, configure, and control cloned Houdini processes which produce live updating renders driven by your interactive Houdini session.
LOP nodes have a debug flag. Normally most LOPs effectively modify the active layer in-place. When a node has the debug flag on, it isolates any changes it makes on a new active layer. This lets you see exactly what changes a particular node added.

This doesn’t effect the final composed stage, but it does use more memory, so you should remember to turn the debug flag off when you're done inspecting the node’s effects.
You can customize the right-click context menu for primitives in the scene graph tree pane using HOUDINIPATH/menus/UsdStagePrimMenu.xml.
There are a few Solaris/USD preferences under Edit ▸ Preferences ▸ Lighting.

Solaris and Karma

USD ¶

USD basics

Introduces a number of USD concepts, and how they relate to Houdini’s USD support.
How LOPs work

How Solaris LOP (lighting operator) nodes work to generate/modify USD.
Solaris user interface

Guide to using the user interface to interact with LOP networks and USD data.
Primitive matching patterns

How to use the USD primitive matching syntax.
LOPS and USD glossary
Solaris scene viewer

Describes the differences/enhancements in the Solaris viewer compared to the Houdini object/SOP viewer.
Using VEX with USD
Writing out USD
Performance tips

Improving interactive workflows in Solaris.
Sample scenes and test assets

Useful scenes and assets for learning Solaris and USD.

Geometry ¶

SOP Geometry I/O

Details of how Houdini converts SOP geometry to USD, and how you can control the process.
Component Builder

The Component Builder tool puts down a network snippet for creating a USD model from SOPs, with support for materials, variants, payloads, and layering.

Layout ¶

Stage Manager

How to work with the Solaris stage effectively.
Edit node

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

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.
Custom Layout Brushes

How to create layout brush digital assets you can use to customize the behavior of the Layout LOP.

Look Development ¶

MaterialX

Houdini has VOP node equivalents of the MaterialX shader nodes. You can build a shader network using these nodes, or import an existing MaterialX-based shader, and use them with Karma (Houdini’s USD renderer).
UDIM paths

You can encode different tiles of a texture space into different texture files, each with its own resolution. You can then specify a texture filename such as kaiju.exr, and Houdini will replace the token with the specific tile address at load time.
Shader translation framework

Describes the Solaris shading framework, including shader node translation to USD primitives.

Karma User Guide ¶

Karma basics and workflows ¶

Karma

Houdini’s Physically Based USD Renderer.
Karma XPU

Houdini’s fast and modern XPU render engine.
Crypromatte and material AOVs in Karma
Cryptomatte

How to generate image maps associating each pixel in the image with the object name and/or material in the original source scene.
Karma light filters

You can attach a light filter to a light to modify the light’s output in different ways.
Karma image and pixel filters
Karma Room Map shader

Projects interior maps onto windows for the impression of 3-dimensional rooms
Houdini Procedural: Ocean

Create oceans with foam from low-resolution input geometry at render time
Houdini Procedural: RBD

Create deformed geometry at render time.
Houdini Procedural: Crowd

Optimize crowd scenes at render time.
Creating a lens shader for Karma
Color management in Houdini

Learn more about OCIO, color spaces, gamma and tone mapping.
Render statistics

How to view various statistics about the render process of an on-going render or rendered image.