Get Volumetric Lightmaps value for a world position

Development Programming & Scripting C++
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1

I am trying to get the VLM value to influence the lighting of particules and customs objects.

Is there a way to access the precomputed values for a position or for a dynamic mesh ?

4

I found a way to do it, I use a custom node in a Material with the following shader.

I juste have WorldPosition in the inputs and I set it with the Absolute World Position

#if PRECOMPUTED_IRRADIANCE_VOLUME_LIGHTING

// Compute indirection UVs from world position

float3 IndirectionVolumeUVs = clamp(WorldPosition * View.VolumetricLightmapWorldToUVScale + View.VolumetricLightmapWorldToUVAdd, 0.0f, .99f);

float3 IndirectionTextureTexelCoordinate = IndirectionVolumeUVs * View.VolumetricLightmapIndirectionTextureSize;

// Get the Brick we need to use

float4 BrickOffsetAndSize = View.VolumetricLightmapIndirectionTexture.Load(int4(IndirectionTextureTexelCoordinate, 0));

float PaddedBrickSize = View.VolumetricLightmapBrickSize + 1;

// Compute the UVs of the texture

// We first offset to the correct Brick and then calculate the UVs inside the brick

float3 BrickTextureUVs = (BrickOffsetAndSize.xyz * PaddedBrickSize + frac(IndirectionTextureTexelCoordinate / BrickOffsetAndSize.w) * View.VolumetricLightmapBrickSize + .5f) * View.VolumetricLightmapBrickTexelSize;

// Compute the Ambient value at the given BrickTextureUVs

return Texture3DSampleLevel(View.VolumetricLightmapBrickAmbientVector, View.VolumetricLightmapBrickAmbientVectorSampler, BrickTextureUVs, 0).xyz;

#else

return float3(1, 1, 1);

#endif