How to obtain the barycentric coordinates of the intersection?

[woAIxuexiSR]

Hi there,

When I use si = scene.ray_intersect(ray) to get the intersection, si.uv seems to be the texture coordinates rather than the barycentric coordinates.

Is there a way to obtain the barycentric coordinates?

[njroussel]

Hi @woAIxuexiSR

Indeed, the SurfaceInteraction3f struct only holds barycentric coordinates in its uv field if the mesh is untextured. If the mesh is textured, then uv is the texture coordinate.
You could theoretically recompute the barycentric coordinates from the si.p and si.prim_index fields, but that would require access to the mesh's datastructures.

If you need this information, I think the easiest way is to add an extra field to the SurfaceInteraction3f struct, fill it during the ray-intersection routing and apply that change wherever required.