how do you add volume lighting to a hlsl in urp?

[laurentopia]

as much as i like graph shader, most powerful shaders out there are hlsl. so how do I add volume lighting to that, is there a block I can copy paste and do my own lighting mixing?

[guycalledfrank]

All useful functions are inside BakeryDecodeLightmap.hlsl. If you have a basic HLSL shader that outputs some color/texture, you can #include "BakeryDecodeLightmap.hlsl" and use my function:

void BakeryVolume_float(float3 posWorld, float3 normalWorld, out float3 sh)

• posWorld is the world position, it should be calculated in VS as mul(unity_ObjectToWorld, IN.Position).xyz andd passed down to PS.
• normalWorld is world normal. Vertex normal can be computed similar to position: normalize(mul((float3x3)unity_ObjectToWorld, IN.Normal)), normal-mapped normals are a bit beyond the scope of this issue (but you can check my PerPixelWorldNormal.shadersubgraph for reference).
• sh is the output color. Just multiply it by albedo and return.

There is also a more advanced function with specular support:

void BakeryVolumeSpec_float(float3 posWorld, float3 normalWorld, float3 viewDir, float smoothness, float3 albedo, float metalness, out float3 diffuseSH, out float3 specularSH)

Additional parameters are:

• viewDir: world-space view vector. Can be computed as normalize(_WorldSpaceCameraPos - posWorld) (maybe with different sign).
• smoothness, albedo, metalness are self-explanatory.
• diffuseSH and specularSH are the outputs. Specular is pre-multiplied by fresnel, you can just add it to the final value.

[laurentopia]

Thanks you! And does BakeryVolumeSpec_float turn into BakeryVolume_float if specularSH isn't used (meaning the compiler strips out the extra computetion)? (Could you add that in the doc so it doesn't get lost in github?)