Fix [#30234] Various problems with CD layers and tesselation, related to modifiers stack.

Should also fix [#30266], [#29451], and partly [#30316].

Here are the changes made by this commit:
* It adds a "dirty" flag to DerivedMesh struct (for now, only DM_DIRTY_TESS_CDLAYERS, but more might be added as needed).
* It adds a new func, DM_update_tessface_data, which assumes tessfaces themselves are valid, but updates tessellated customdata from their poly/loop counter parts.
* At end of modstack, when valid tessellated faces are present in finaldm , but the cdlayers dirty flag is set, call that function (instead of recomputing the whole tessellation).
* Edits to the codes concerned (UVProject, DynamicPaint, and Subsurf modifiers).
* Also add to subsurf dm generation code the creation of a CD_POLYINDEX layer (mandatory for DM_update_tessface_data to work well, and imho all tessellated dm should have one).

Note: some pieces of old code are just #if 0’ed, will clean them later.

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_mesh.h b/source/blender/blenkernel/BKE_mesh.h
index c5d137b086f..546fd2bb354 100644
--- a/source/blender/blenkernel/BKE_mesh.h
+++ b/source/blender/blenkernel/BKE_mesh.h
@@ -297,7 +297,7 @@ void BKE_mesh_tessface_calc(struct Mesh *mesh);
 void BKE_mesh_tessface_ensure(struct Mesh *mesh);
 void BKE_mesh_tessface_clear(struct Mesh *mesh);
 
-/*convert a triangle of loop facedata to mface facedata*/
+/* Convert a triangle or quadrangle of loop/poly data to tessface data */
 void mesh_loops_to_mface_corners(struct CustomData *fdata, struct CustomData *ldata,
                                  struct CustomData *pdata, int lindex[4], int findex,
                                  const int polyindex, const int mf_len,