# PBR Materials

## KHR Texture Transforms

Texture repeats for PBR materials on prims are based on the [KHR\_texture\_transform](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_texture_transform) spec, and thus should be expected to behave according to the spec.

PBR materials should have approximately correct lighting based on the normal texture:

- With default texture transforms, assuming the prim or model has correct normals and tangents
- With a texture transform applied, especially rotation or negative scale
- With a texture animation applied via `llSetTextureAnim`, especially a rotation animation
    - Note: Texture animations are not guaranteed to loop when a PBR texture transform is applied