Bugfix: avoid reading from an OpenGL buffer mapped write-only.

When set to solid-shading, GPU_update_grid_buffers was calling
normal_quad_v3 to output into a mapped buffer, but normal_quad_v3
reads as well as writes.

This fix actually makes a huge performance difference with my drivers
(Gallium/Radeon).

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/gpu/intern/gpu_buffers.c b/source/blender/gpu/intern/gpu_buffers.c
index ff269e2050f..00e34b41faf 100644
--- a/source/blender/gpu/intern/gpu_buffers.c
+++ b/source/blender/gpu/intern/gpu_buffers.c
@@ -1427,11 +1427,14 @@ void GPU_update_grid_buffers(GPU_Buffers *buffers, DMGridData **grids,
 					   that is what opengl will use */
 					for(j = 0; j < gridsize-1; ++j) {
 						for(k = 0; k < gridsize-1; ++k) {
-							normal_quad_v3(vert_data[(j+1)*gridsize + (k+1)].no,
+							float fno[3];
+							normal_quad_v3(fno,
 								grid[(j+1)*gridsize + k].co,
 								grid[(j+1)*gridsize + k+1].co,
 								grid[j*gridsize + k+1].co,
 								grid[j*gridsize + k].co);
+
+							copy_v3_v3(vert_data[(j+1)*gridsize + (k+1)].no, fno);
 						}
 					}
 				}