Fix T77867: Link Duplicate Object crashes during batch creation

When using link duplicated objects it could happen that one object is
calculating the GPUBuffers and the second object is marking these
buffers invalid. This introduces threading issues.

This patch fixes this by combining the surface and surface per material
batches. Most likely the surface per material batches are used and when
requested you will most likely need the surface batch for the depth
tests and overlays.

During tests it slightly improves performance as batches aren't thrown
away without using it.

After this patch we can add a quick path for meshes with one material
and two materials.

Alternative approaches that have been checked:
- sync extraction per object: reduced performance to much (-15%)
  ({D8292})
- post checks: reduced the threading issues, but didn't solve it.
- separating preparation and execution of the extraction ({D8312})

Reviewed By: Clément Foucault

Differential Revision: https://developer.blender.org/D8329

1 files changed, 1 insertions, 2 deletions

diff --git a/source/blender/draw/intern/draw_cache_extract.h b/source/blender/draw/intern/draw_cache_extract.h
index f05e8e2f9d6..4156e2e79d8 100644
--- a/source/blender/draw/intern/draw_cache_extract.h
+++ b/source/blender/draw/intern/draw_cache_extract.h
@@ -170,8 +170,7 @@ typedef enum DRWBatchFlag {
   MBC_WIRE_EDGES = (1 << 23),
   MBC_WIRE_LOOPS = (1 << 24),
   MBC_WIRE_LOOPS_UVS = (1 << 25),
-  MBC_SURF_PER_MAT = (1 << 26),
-  MBC_SKIN_ROOTS = (1 << 27),
+  MBC_SKIN_ROOTS = (1 << 26),
 } DRWBatchFlag;
 
 #define MBC_EDITUV \