Draw Cache: extract tris in parallel ranges

The `ibo.tris` extraction in multithread is currently only done if the
mesh has only 1 material.

Now we cache a map indicating the index of each polygon after sort and
thus allow the extraction of tris with materials in multithreaded.

As caching is a heavy operation and was already being performed in
multi-thread for triangle offsets, no significant improvements are
expected.

The benefit will be much greater when we can skip updating the cache
while transforming a geometry.

**Profiling:**
||master:|PATCH:
|---|---|---|
|large_mesh_editing_materials:|Average: 13.855380 FPS|Average: 15.525684 FPS
||rdata 9ms iter 36ms (frame 71ms)|rdata 9ms iter 29ms (frame 64ms)
|subdiv_mesh_final_only_materials:|Average: 28.113742 FPS|Average: 28.633599 FPS
||rdata 0ms iter 1ms (frame 36ms)|rdata 0ms iter 1ms (frame 35ms)

1.1x overall speedup

Differential Revision: https://developer.blender.org/D11445

1 files changed, 5 insertions, 5 deletions

diff --git a/source/blender/draw/intern/draw_cache_extract.h b/source/blender/draw/intern/draw_cache_extract.h
index f2f769534ca..7dc468d1a73 100644
--- a/source/blender/draw/intern/draw_cache_extract.h
+++ b/source/blender/draw/intern/draw_cache_extract.h
@@ -84,9 +84,9 @@ typedef enum eMRDataType {
   MR_DATA_LOOSE_GEOM = 1 << 4,
   /** Force loop normals calculation. */
   MR_DATA_TAN_LOOP_NOR = 1 << 5,
-  MR_DATA_MAT_OFFSETS = 1 << 6,
+  MR_DATA_POLYS_SORTED = 1 << 6,
 } eMRDataType;
-ENUM_OPERATORS(eMRDataType, MR_DATA_MAT_OFFSETS)
+ENUM_OPERATORS(eMRDataType, MR_DATA_POLYS_SORTED)
 
 #ifdef __cplusplus
 extern "C" {
@@ -170,10 +170,10 @@ typedef struct MeshBufferExtractionCache {
   } loose_geom;
 
   struct {
-    int *tri;
+    int *tri_first_index;
+    int *mat_tri_len;
     int visible_tri_len;
-  } mat_offsets;
-
+  } poly_sorted;
 } MeshBufferExtractionCache;
 
 #define FOREACH_MESH_BUFFER_CACHE(batch_cache, mbc) \