This page gives some basic details about the Color Channel render pass and what you can do with it in Houdini.
Overview
The Color Channel is a container node that allows the output of almost every render channel available in V-Ray. It allows you to extract different color components from the image (i.e. Diffuse, Reflections, Refractions, etc.) to use used later for tasks like compositing.
UI Path
||out Network|| > V-Ray Render Elements node > V-Ray > Render Channel > Color Channel
Parameters
The parameters for this render channel appear in the Parameters tab under the out Network and within the render channels node.
Type – Allows you to select which color information to extract from the image as a separate channel. For more details, please see the Channel Types table below.
Name – The text added to the end of the rendered file, when saved as a separate file (e.g. myrender.colorchannel.vrimg).
Consider for Anti-Aliasing – When enabled, anti-aliasing will be used where possible.
Filtering – Applies the image filter to this channel. Image filter settings are in the Image Sampler tab of V-Ray Renderer node.
Color Mapping – When enabled, the Color Mapping options in the render settings will be applied to the current render channel.
Derive Raw Channels – Generates data in the raw channels by combining the respective color and the filter color channels.
VFB Color Corrections – Applies the post render color adjustments made from the VFB.
Channel Types
The table below provides a list of the channels that can be separated out with the Color Channel render pass.
| Type | Description |
|---|---|
| Atmosphere | Atmospheric effects, such as Environment Fog. |
Diffuse | Pure diffuse surface color. |
| Reflection | Reflections on the surface. |
| Refraction | Refractions of a surface. |
| Self Illumination | Self-illumination of the surface. |
| Shadow | Diffuse light blocked by other objects. |
| Specular | Surface specular highlights. |
| Lighting | Diffuse direct surface lighting. |
| GI | The diffuse surface global illumination. Only present if Global illumination is enabled. |
| Caustics | The caustics on the material. These caustics are present only when the Caustics option of V-Ray is enabled. This channel does not include GI caustics. |
| Raw GI | Raw diffuse global illumination (not multiplied by the diffuse surface color). Only present if Global illumination is enabled. |
| Raw Lighting | Raw diffuse direct illumination before it's multiplied by the diffuse surface color. |
| Raw Shadow | Raw light blocked by other objects. |
| Velocity | Surface velocity of an object. This render element is useful for generating motion blur in post-production. |
| Render ID | Node render ID of the object that contributes most to the pixel value. |
| Material ID | Material ID of the object. |
| Node ID | Returns solid un-shaded colors to represent a numerical identifier set through that object's Attributes, Object Property, or assigned material. Useful for selection masks. .EXR and .vrimg formats store as integer values. |
| Z-Depth | Z-depth of the surface. |
| Reflection Filter | Reflection filter (the color by which the raw reflections are multiplied to give the final surface reflection). This can be considered an alpha channel for reflections. |
| Raw Reflection | Pure surface reflection before it is multiplied by the reflection filter color. |
| Refraction Filter | The refraction filter mitigates the raw refraction layer. This render element returns the color by which the raw refractions are multiplied to give the final surface refraction. This can be considered an alpha channel for refractions. |
| Raw Refraction | Pure surface refraction before it is multiplied by the refraction filter color. |
| Real Color | Shows the original colors that were clamped or adjusted with Color Mapping. |
| Normal | Surface normals in screen space (which is not the same as camera space). To output the normals in camera/object/world space, use Maya's Sampler Info utility texture node. |
| Background | Image background, such as any Background Texture specified in the Environment render settings. |
| Alpha | Alpha transparency. |
| Color | Generic render element container used for referencing other render elements of type RenderChannelColor containing color information . |
| Wire Color | The wire color of the object as set in the 3ds Max scene. This can be used to generate masks for the objects based on their wire color. |
| Matte / Shadow | Matte shadow part of the image. |
| Total Lighting | Both direct and indirect lighting in the scene. |
| Raw Total Lighting | Sum of all raw lighting, both direct and indirect. |
| Bump / Normal | Normals generated by bump maps, in screen space (which is not the same as camera space). Use the VRaySamplerInfo utility texture node to get the normals in camera, world or object space. |
| Samplerate | Shows an image where the pixel brightness is directly proportional to the number of samples taken at that pixel. |
| SSS | Renders just the subsurface part of the V-Ray SSS material on a separate layer. |
| DR Bucket | Identifies the render node responsible for rendering a bucket during distributed rendering. |
| Reflection Glossiness | Returns a float value that corresponds with the Reflection Glossiness value of an object's material. |
| Reflection Hilights | Returns a float value that corresponds with the Highlight Glossiness value of an object's material. |
| Refraction Glossiness | Returns a float value that corresponds to the Refraction Glossiness value of an object's material. |
| Reflection IOR | Stores floating-point information that corresponds to the Fresnel IOR values of scene objects' materials. |
| Material Render ID | This render element shows solid unshaded color masks based on the selected Material ID color. |
| Noise Level | Outputs the noise level for pixels. Same as the noiseLevel render element produced by the VRayDenoiser, but as a standalone render element. |