maiden rivet
Neither Metal nor WebGPU have reduction samplers, so for my Hi-Z occlusion culling I need to emulate them inside of my shaders for those platforms.
Where can I find information about what pixels the reduction sampler chooses in the various cases? (ie right in the middle of a pixel, towards the side of a pixel, at the texture edge, etc)
pearl meteor
Are you talking about min/max filter modes? It’s the same as what’s used for bilinear filtering.
maiden rivet
Yes, I'm trying to search for the bilinear sampling pattern but I haven't been able to find anything for that either
pearl meteor
If mips aren’t involved you can use Gather to get the 4 texels used for filtering
maiden rivet
This is the line I need to emulate:
//sample the depth pyramid at that specific level
float depth = textureLod(sampler2D(depthPyramid, depthPyramidSampler), ndcCorners[i], miplevel).x;
I'm not seeing a textureGatherLod function in my searching. Is there a way to specify a specific mip level when gathering?
pearl meteor
I don’t think there’s a gather that lets you select the mip level
maiden rivet
that seems like a pretty big gap in API coverage. is there a reason for that?
pearl meteor
Anyhow I'm not sure where it's called out in the specs, but it should be something like this for getting the 4 texels used for bilinear: https://github.com/TheRealMJP/DXRPathTracer/blob/master/SampleFramework12/v1.02/Graphics/Textures.h#L96
pearl meteor
that seems like a pretty big gap in API coverage. is there a reason for that?
I think it was just not something that all hardware supported at the time that Gather was added