About LOD calculation

Vulkan
1

Hello, I heard as follow

Fragment shader is invoked per location in rasterized triangles
Texture mapping process including LOD calculation is performed during fragment shader invocation
GPU driver evaluates horizontal derivative magnitude and vertical derivative magnitude for 2 by 2 pixel grids
GPU driver evaluates both derivative magnitudes for each fragment, hence that 2 by 2 pixel grid is sliding window (per each fragment)

Are all statements above correct?
Thank you

2

Broadly, yes you are correct.

One minor correction would be that it’s 2x2 fragment quads, not 2x2 pixel quads. It is possible to have more fragments than pixels, and more pixels than fragments, depending on how the API is being used.

1 Like
3

Hello, Peter
I understand now
Thank you for your help and have a nice weekend