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, 12 insertions, 6 deletions

diff --git a/source/blender/editors/gpencil/gpencil_fill.c b/source/blender/editors/gpencil/gpencil_fill.c
index 1b69947b294..9860c75f290 100644
--- a/source/blender/editors/gpencil/gpencil_fill.c
+++ b/source/blender/editors/gpencil/gpencil_fill.c
@@ -127,6 +127,8 @@ typedef struct tGPDfill {
   struct bGPDstroke *gps_mouse;
   /** Pointer to report messages. */
   struct ReportList *reports;
+  /** For operations that require occlusion testing. */
+  struct ViewDepths *depths;
   /** flags */
   short flag;
   /** avoid too fast events */
@@ -1374,7 +1376,7 @@ static void gpencil_get_depth_array(tGPDfill *tgpf)
     /* need to restore the original projection settings before packing up */
     view3d_region_operator_needs_opengl(tgpf->win, tgpf->region);
     ED_view3d_depth_override(
-        tgpf->depsgraph, tgpf->region, tgpf->v3d, NULL, V3D_DEPTH_NO_GPENCIL, NULL);
+        tgpf->depsgraph, tgpf->region, tgpf->v3d, NULL, V3D_DEPTH_NO_GPENCIL, &tgpf->depths);
 
     /* Since strokes are so fine, when using their depth we need a margin
      * otherwise they might get missed. */
@@ -1385,6 +1387,7 @@ static void gpencil_get_depth_array(tGPDfill *tgpf)
     int interp_depth = 0;
     int found_depth = 0;
 
+    const ViewDepths *depths = tgpf->depths;
     tgpf->depth_arr = MEM_mallocN(sizeof(float) * totpoints, "depth_points");
 
     for (i = 0, ptc = tgpf->sbuffer; i < totpoints; i++, ptc++) {
@@ -1392,11 +1395,9 @@ static void gpencil_get_depth_array(tGPDfill *tgpf)
       int mval_i[2];
       round_v2i_v2fl(mval_i, &ptc->x);
 
-      if ((ED_view3d_autodist_depth(tgpf->region, mval_i, depth_margin, tgpf->depth_arr + i) ==
-           0) &&
-          (i &&
-           (ED_view3d_autodist_depth_seg(
-                tgpf->region, mval_i, mval_prev, depth_margin + 1, tgpf->depth_arr + i) == 0))) {
+      if ((ED_view3d_depth_read_cached(depths, mval_i, depth_margin, tgpf->depth_arr + i) == 0) &&
+          (i && (ED_view3d_depth_read_cached_seg(
+                     depths, mval_i, mval_prev, depth_margin + 1, tgpf->depth_arr + i) == 0))) {
         interp_depth = true;
       }
       else {
@@ -1771,6 +1772,11 @@ static void gpencil_fill_exit(bContext *C, wmOperator *op)
       ED_region_draw_cb_exit(tgpf->region->type, tgpf->draw_handle_3d);
     }
 
+    /* Remove depth buffer in cache. */
+    if (tgpf->depths) {
+      ED_view3d_depths_free(tgpf->depths);
+    }
+
     /* finally, free memory used by temp data */
     MEM_freeN(tgpf);
   }