Sub-Surface Lightmap Write

Category: Lightmap

Shader Family: Lightmap

Output: Lightmap

The Sub-Surface Lightmap Write shader is the lightmapping shader that is used to create lightmaps for fast subsurface scattering effects. This shader creates a lightmap and stores the front and back surfaces, their depth, and irradiant light intensities in one or more specially formatted lightmaps.

Choose User Tools Create SSS Lightmap in the render tree to create an Image Clip with a Writable Image Source, where you can define the output options for the lightmap image.

Lightmap Group	The name of the "scatter group" created with automatic lightmap generation. All objects and materials that use the same scatter group will scatter light into each other.
Lightmap Size (%)	Specifies the size of the lightmap, expressed as a percentage of the final rendered image resolution. Normally, this value should not need to be higher than 50%. However, should the rendered image still contain artifacts, you can set it higher than this.
Scatter Bias	Adjusts the light in the lightmap to favor back scattering (light from behind the camera scatters back towards the camera) when using negative values and forward scattering when using positive values. The technical range is -1 to 1, but generally only small values (-0.2 to 0.2) make visual sense.

Render Tree Usage

The Sub-Surface Lightmap Write shader evaluates the object's render tree directly. Whatever portion of the render tree is connected to the Lightmap Write's input port is computed and written to a texture file.

Any illumination shader can be used to sample the lighting in the model for the lightmap. For example, you can use a Lambert or even experiment with a Phong and the scattering of specular reflections.

You must manually generate the lightmap image for fast subsurface scattering effects created when using the pre-packaged Fast Subsurface Scattering Shader Compounds [Materials and Shaders].