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 later for tasks like compositing.


Parameters

The parameters for this render channel appear in the Parameters tab under the out Network and within the render elements node.

Type – Selects 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).

Deep Output – Specifies whether to include this render element in deep images.

Color Mapping – When enabled, the Color Mapping options in the render settings are applied to the current render channel.

Consider For AA – When enabled, anti-aliasing is 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.

Denoise – Enables the render element's denoising, provided the V-Ray Denoiser render element is present.

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.


TypeDescription
AlphaAlpha transparency.
AtmosphereAtmospheric effects, such as Environment Fog.
BackgroundImage background, such as any Background Texture specified in the Environment render settings.
CausticsThe 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.

Diffuse

Pure diffuse surface color.
Direct LightDiffuse direct surface lighting.
GIThe diffuse surface global illumination. Only present if Global illumination is enabled.
Material IDMaterial ID of the object.
Matte ShadowMatte shadow part of the image.
MetalnessShows where a V-Ray Material with Metalness is applied.
Noise LevelOutputs the noise level for pixels. Same as the noiseLevel render element produced by the V-Ray Denoiser, but as a standalone render element.
Raw Diffuse FilterA solid mask of raw diffuse surface color information not affected by fresnel falloff.
Raw Direct LightRaw diffuse direct illumination before it's multiplied by the diffuse surface color.
Raw GIRaw diffuse global illumination (not multiplied by the diffuse surface color). Only present if Global illumination is enabled.
Raw ReflectionPure surface reflection before it is multiplied by the reflection filter color.
Raw Reflection FilterA solid mask of raw reflection information not affected by fresnel falloff.
Coat FilterReflection filter for V-Ray Material Coat layer.
Sheen FilterReflection filter for V-Ray Material Sheen layer.
Raw RefractionPure surface refraction before it is multiplied by the refraction filter color.
Raw Refraction FilterA solid mask of raw refraction information not affected by fresnel falloff.
Raw ShadowRaw light blocked by other objects.
Raw Total LightSum of all raw lighting, both direct and indirect.
ReflectionReflections on the surface.
Reflection FilterReflection 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.
Reflection IORStores floating-point information that corresponds to the Fresnel IOR values of scene objects' materials.
RefractionRefractions of a surface.
Refraction FilterThe 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.
Refraction GlossinessReturns a float value that corresponds to the Refraction Glossiness value of an object's material.
RoughnessBakes the Reflection Roughness values in a scene, creating a black and white image.
Sample RateShows an image where the pixel brightness is directly proportional to the number of samples taken at that pixel.
Self IlluminationSelf-illumination of the surface.
ShadowDiffuse light blocked by other objects.
SpecularSurface specular highlights.
SSSRenders just the subsurface part of the V-Ray SSS material on a separate layer.
Total LightingBoth direct and indirect lighting in the scene.
Unclamped ColorShows the original colors that were clamped or adjusted with Color Mapping.