outdated thread
2 things here. do whatever to the shaders.
the loading pattern is the virtual texture system streaming in higher res tiles. not a shader issue.
But it only happens when I change the GGX function?
Bump.
Why is the does changing the BDRF function break VT maps?
You have to normalize it as well for PBR
Here’s the full Blinn Phong with Metallic and Fresnel
The square texture pattern is probably not caused by the BRDF distribution alone. Changing D_GGX alters assumptions around roughness and specular filtering, so it can expose issues with mip selection or texture filtering.
If you’re mainly chasing performance, I’d benchmark the shader cost first, as replacing GGX may not provide a significant gain when the rest of the lighting pipeline remains unchanged. Hybrid BRDFs are possible, but you’d likely need material-level branching or separate shading models, and the actual benefit depends on how those paths compile and execute. The other BRDF functions in BRDF.ush are generally building blocks/reference implementations, not automatically selectable models without modifying the relevant shading code and recompiling shaders.