Unity Shader reference Notes - Multi Light

multi light is done in different passes.

base pass

• First directional light is in the base pass
• base pass is drawn no matter if there is a directional light.
• declare in Tags before CGPROGRAM after pass
• vertex light need to be in base pass , declare with VERTEXLIGHT_ON

          

add pass

• Enable the blending between base and add pass by Blend One One
• support directional / point / spot light  : multi_compile_fwdadd

          

include file

include file aim to reuse code include all the vertex / fragment function code and some variables declaration and includes files.
Include is just simple replace all the code in the included file to the including file.

• a typical including declare is like this. It prevent include the same files twice.

          

• include file ends with "cginc"
• base pass and add pass can use the same include file

support different lights

• according to different light type calculate the light.dir differently
• UNITY_LIGHT_ATTENUATION(atten , vertextOut , vertextOut. worldPos ) provide the attenuation for point and spot light, it will always be 1 for directional light.

          

vertex light

• four vertex lights can be used. When pixel lights reach the set limited, Unity switch to vertex light.
• to set the pixel light limitation : edit -> project setting -> quality -> pixel light count
• declare in base pass   #pragma multi_compile _ VERTEXLIGHT_ON
• In vertex out structure declare vertexLightcolor to pass the vertex light to fragment function

• light.

          

• calculate the vertex light using the function ShadePointLight()

          Unity records the vertex lights position, color and attenuation in the following variable

• vertex light is put into indirect light

          
One thing on vertex light is very important
To force vertex light , put the vertex light to not important render mode in light setting

environment Light

• environmental light is captured by spherical harmonic function in Unity.
• the function should only be used in the base pass
• the function should contribute to the indirect diffuse light.