Subdiv: Add ptex offsets to a subdiv structure

This is something what we need to know quite often from various places.
Added it as a cached value in Subdiv itself, so it can be queried easily
from any area.

Shouldn't be a problem from memory usage point of view, it's 4MB per
1M faces coarse mesh. This is very low percentage of mesh itself, and
even lower percentage of highres subdivided mesh.

1 files changed, 23 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/subdiv.c b/source/blender/blenkernel/intern/subdiv.c
index f847d62018a..82275b7305f 100644
--- a/source/blender/blenkernel/intern/subdiv.c
+++ b/source/blender/blenkernel/intern/subdiv.c
@@ -118,5 +118,28 @@ void BKE_subdiv_free(Subdiv *subdiv)
 		openSubdiv_deleteTopologyRefiner(subdiv->topology_refiner);
 	}
 	BKE_subdiv_displacement_detach(subdiv);
+	if (subdiv->cache_.face_ptex_offset != NULL) {
+		MEM_freeN(subdiv->cache_.face_ptex_offset);
+	}
 	MEM_freeN(subdiv);
 }
+
+int *BKE_subdiv_face_ptex_offset_get(Subdiv *subdiv)
+{
+	if (subdiv->cache_.face_ptex_offset != NULL) {
+		return subdiv->cache_.face_ptex_offset;
+	}
+	const int num_coarse_faces =
+	        subdiv->topology_refiner->getNumFaces(subdiv->topology_refiner);
+	subdiv->cache_.face_ptex_offset = MEM_malloc_arrayN(
+	        num_coarse_faces, sizeof(int), "subdiv face_ptex_offset");
+	int ptex_offset = 0;
+	for (int face_index = 0; face_index < num_coarse_faces; face_index++) {
+		const int num_ptex_faces =
+		        subdiv->topology_refiner->getNumFacePtexFaces(
+		                subdiv->topology_refiner, face_index);
+		subdiv->cache_.face_ptex_offset[face_index] = ptex_offset;
+		ptex_offset += num_ptex_faces;
+	}
+	return subdiv->cache_.face_ptex_offset;
+}