You can right-click shaders, Arnold VOP networks and ROPs to upgrade them to the current version of Arnold and HtoA. You can also globally convert all the deprecated shaders in the scene from the Arnold menu. Conversion scripts for the deprecated standard and hair shaders, the Arnold ROP from a previous version of HtoA and the discontinued alSurface and alHair shaders are provided. For shaders, the conversion will attempt to match the look as closely as possible with a standard_surface or standard_hair shader.
Shaders are created within Arnold Shader Network nodes. These nodes are also used for Light Filters and Environment Effects.
In the SHOP context Tab > Arnold > Arnold Shader Network to create an arnold_vopnet1 node. Double clicking or pressing "I" enters a custom VEX builder context where Arnold shaders and nodes can be networked together.
You can now create shaders the new Houdini way in /mat in the arnold_materialbuilder vop network as well as the old way in /shop in the arnold_vopnet vop network. Use the material flag to enable picking of the vopnet as a material at the object level.
Output Nodes
There are three types of output depending on the purpose of the shader network; Material, Light, and Environment. The result of the shader network must be connected to the input of the relevant output node. Multiple Outputs of different types can be contained within the same shader network. If multiple outputs of the same type exist, Arnold will use the first one translated by HtoA.
Material Output
- surface: To connect the color output of a surface shader like Standard Surface or Lambert.
- displacement: Connect a bitmap texture (image node) or procedural texture, like noise, to displace the geometry surface.
- volume: For connecting a Volume Collector shader.
Light Output
- color: For attaching a shader (like a Physical Sky) to be used as the color of a light.
- light_filter #: Light Filter nodes are connected here. As each is connected another input will appear.
Environment Output
- atmosphere: For connecting the atmosphere nodes fog and volumetric scattering.
- background: For connecting background shaders like Sky or Physical Sky.
Shader Assignment
To assign a vopnet drag it from the SHOP onto the geometry or use the Operator Chooser in the geometry Material tab.
The 'jump to operator' in the material tab will go to the Arnold shader network, rather than jumping to the shader inside. This is Houdini's behavior because you're assigning a SHOP and thus it brings you to it, not inside.
Export Arnold Materials
You can export materials in an arnold_vopnet or from an OUT_material VOP by right-clicking with the context-sensitive menu. This exports all of the shader graphs connected (surface, displacement, and volume).
Shader List
These are the available shaders and nodes.
Core Shaders
AOV Shaders
User Data
Shading State
Ramp Shaders
| Math Shaders
| Utility Shaders
Data Types
VolumesEnvironmentLight Filters |