ScriptableRenderPipeline/com.unity.render-pipelines.high-definition/HDRP/Lighting/Forward.hlsl

// There is two kind of lighting architectures.
// Those that are control from inside the "Material".shader with "Pass" concept like forward lighting. Call later forward lighting architecture.
// Those that are control outside the "Material".shader in a "Lighting".shader like deferred lighting. Call later deferred lighting architecture.

// When dealing with deferred lighting architecture, the renderPipeline is in charge to call the correct .shader.
// renderPipeline can do multiple call of various deferred lighting architecture.
// (Note: enabled variant for deferred lighting architecture are in deferred.shader)
// When dealing with forward lighting architecture, the renderPipeline must specify a shader pass (like "forward") but it also need
// to specify which variant of the forward lighting architecture he want (with cmd.EnableShaderKeyword()).

// The purpose of the following pragma is to define the variant available for "Forward" Pass in "Material".shader.
// If only one keyword is present it mean that only one type of forward lighting architecture is supported.

// Must match name in GetKeyword() method of forward lighting architecture .cs file
// #pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS -> can't use a pragma from include... (for now)
// For forward transparent are always cluster and opaque can be either cluster or fptl (sadly we have no to do multicompile only if opaque)
// Moreover, we would like to do it only for LIGHTLOOP_TILE_PASS variant...
// #pragma multi_compile USE_FPTL_LIGHTLIST USE_CLUSTERED_LIGHTLIST