Modifier Stack: Limit calculation to required data.

This commit upgrades the modifier stack to only calculate the data which is
needed, either by modifiers further down the stack or by other functions at
the end of the stack (e.g. drawing functions).

This speeds up modifier stack recalculation, especially where vertex
groups and UV coordinates are concerned. For example, a mesh with an Armature
modifier followed by a Subsurf modifier would previously have required the
Subsurf modifier to interpolate all the vertex groups in the mesh, slowing
down modifier calculations considerably. With this update, vertex group data
is not propagated beyond the Armature modifier, so calculations are faster.

Note that this depends on the order of modifiers in the stack. If the Armature
and Subsurf modifiers were swapped in the above example, the Subsurf modifier
would have to interpolate vertex groups, as they are needed by the Armature
modifier.

1 files changed, 4 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_editVert.h b/source/blender/blenlib/BLI_editVert.h
index d39cd748fb1..e81e7db57ca 100644
--- a/source/blender/blenlib/BLI_editVert.h
+++ b/source/blender/blenlib/BLI_editVert.h
@@ -164,6 +164,10 @@ typedef struct EditMesh
 		 * to derived final, care should be taken on release.
 		 */
 	struct DerivedMesh *derivedCage, *derivedFinal;
+	/* the custom data layer mask that was last used to calculate
+	 * derivedCage and derivedFinal
+	 */
+	int lastDataMask;
 
 	char retopo_mode; /* 0=OFF, 1=ON, 2=PAINT */
 	struct RetopoPaintData *retopo_paint_data;