How to modify lightmap in C++?

Development Rendering
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1

hi friends, I try to add some “post process” into lightmap after the lightmaps are baked.

however, I encountered some problems at the veryfirst step:

			UStaticMeshComponent *umc = it->FindComponentByClass<UStaticMeshComponent>();

			const FMeshMapBuildData* MeshMapBuildData = umc->GetMeshMapBuildData(umc->LODData[0]);

			if (MeshMapBuildData != nullptr)
			{
				FLightMap2D *LightMap2D = MeshMapBuildData->LightMap->GetLightMap2D();

				if (LightMap2D != nullptr)
				{
					UTexture2D *RealTexture2D = LightMap2D->GetTexture(1); // get the low quality

					FTexture2DMipMap *ZeroMipMap = &RealTexture2D->PlatformData->Mips[0];
					FByteBulkData *RawData = &ZeroMipMap->BulkData;
					if (RawData->GetElementCount() > 0)
					{ // this ElementCound is always 0

The Elementcount of bulkdata is always 0, it is true that lightmaps are not cpu-readable, so I cannot read the values and modify it (like darken a part of it) ?

2

Does really no one care about modifying lightmap?

3

What I do to kind of modify the lightmap data is using the LockMip function inside UTexture2D::Source

FColor* Mip0 = (FColor*)RealTexture2D->Source.LockMip(0);

Then I can modify Mip0, and after that just Unlock the mip.