GPencil and Annotation: Use cached depth to perform depth testing operations

Operations such as erasing with occlusion and drawing on the surface
require reading the depth buffer.

However, this is being done with minimal efficiency.

Currently, to read the depth corresponding to each point of the new stroke,
a ReadPixel is called to send a message to the GPU and read the depth of
the corresponding pixel in the VRAM.

The communication between GPU and CPU is known to be a slow operation so
it is good to be avoided.

Therefore, save the entire depth buffer in a cache to be read directly
from the RAM.

(Also the `ED_view3d_autodist_depth` and `ED_view3d_autodist_depth_seg` have
been removed since they are no longer used).

Reviewed By: antoniov, fclem

Differential Revision: https://developer.blender.org/D10894

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/editors/gpencil/gpencil_intern.h b/source/blender/editors/gpencil/gpencil_intern.h
index b6730cb123b..3f3fd4fff39 100644
--- a/source/blender/editors/gpencil/gpencil_intern.h
+++ b/source/blender/editors/gpencil/gpencil_intern.h
@@ -155,6 +155,8 @@ typedef struct tGPDprimitive {
   struct Material *material;
   /** current brush */
   struct Brush *brush;
+  /** For operations that require occlusion testing. */
+  struct ViewDepths *depths;
 
   /** Settings to pass to gp_points_to_xy(). */
   GP_SpaceConversion gsc;