Refactor: Do not keep a copy of depth buffer in RegionView3D

The depth cache (located in `RegionView3D::depths`) is used for quick
and simple occlusion testing in:
- particle selection,
- "Draw Curve" operator and
- "Interactive Light Track to Cursor" operator,

However, keeping a texture buffer in cache is not a recommended practice.

For displays with high resolution like 8k this represents something
around 132MB.

Also, currently, each call to `ED_view3d_depth_override` invalidates
the depth cache. So that depth is never reused in multiple calls from
an operator (this was not the case in blender 2.79).

This commit allows to create a depth cache and release it in the same
operator. Thus, the buffer is kept in cache for a short time, freeing
up space.

No functional changes.

6 files changed, 44 insertions, 99 deletions

diff --git a/source/blender/editors/space_view3d/space_view3d.c b/source/blender/editors/space_view3d/space_view3d.c
index 8c356bc1600..c9f345b3123 100644
--- a/source/blender/editors/space_view3d/space_view3d.c
+++ b/source/blender/editors/space_view3d/space_view3d.c
@@ -786,12 +786,6 @@ static void view3d_main_region_free(ARegion *region)
       RE_engine_free(rv3d->render_engine);
     }
 
-    if (rv3d->depths) {
-      if (rv3d->depths->depths) {
-        MEM_freeN(rv3d->depths->depths);
-      }
-      MEM_freeN(rv3d->depths);
-    }
     if (rv3d->sms) {
       MEM_freeN(rv3d->sms);
     }
@@ -815,7 +809,6 @@ static void *view3d_main_region_duplicate(void *poin)
       new->clipbb = MEM_dupallocN(rv3d->clipbb);
     }
 
-    new->depths = NULL;
     new->render_engine = NULL;
     new->sms = NULL;
     new->smooth_timer = NULL;
diff --git a/source/blender/editors/space_view3d/view3d_draw.c b/source/blender/editors/space_view3d/view3d_draw.c
index 0bc19887118..c024bab355d 100644
--- a/source/blender/editors/space_view3d/view3d_draw.c
+++ b/source/blender/editors/space_view3d/view3d_draw.c
@@ -2221,7 +2221,7 @@ int ED_view3d_backbuf_sample_size_clamp(ARegion *region, const float dist)
 /** \name Z-Depth Utilities
  * \{ */
 
-void view3d_update_depths_rect(ARegion *region, ViewDepths *d, rcti *rect)
+void view3d_depths_rect_create(ARegion *region, rcti *rect, ViewDepths *r_d)
 {
   /* clamp rect by region */
   rcti r = {
@@ -2242,70 +2242,44 @@ void view3d_update_depths_rect(ARegion *region, ViewDepths *d, rcti *rect)
   int h = BLI_rcti_size_y(rect);
 
   if (w <= 0 || h <= 0) {
-    if (d->depths) {
-      MEM_freeN(d->depths);
-    }
-    d->depths = NULL;
-
-    d->damaged = false;
+    r_d->depths = NULL;
+    return;
   }
-  else if (d->w != w || d->h != h || d->x != x || d->y != y || d->depths == NULL) {
-    d->x = x;
-    d->y = y;
-    d->w = w;
-    d->h = h;
 
-    if (d->depths) {
-      MEM_freeN(d->depths);
-    }
-
-    d->depths = MEM_mallocN(sizeof(float) * d->w * d->h, "View depths Subset");
+  r_d->x = x;
+  r_d->y = y;
+  r_d->w = w;
+  r_d->h = h;
 
-    d->damaged = true;
-  }
+  r_d->depths = MEM_mallocN(sizeof(float) * w * h, "View depths Subset");
 
-  if (d->damaged) {
+  {
     GPUViewport *viewport = WM_draw_region_get_viewport(region);
-    view3d_opengl_read_Z_pixels(viewport, rect, d->depths);
+    view3d_opengl_read_Z_pixels(viewport, rect, r_d->depths);
     /* Range is assumed to be this as they are never changed. */
-    d->depth_range[0] = 0.0;
-    d->depth_range[1] = 1.0;
-    d->damaged = false;
+    r_d->depth_range[0] = 0.0;
+    r_d->depth_range[1] = 1.0;
   }
 }
 
 /* Note, with nouveau drivers the glReadPixels() is very slow. T24339. */
-static void view3d_depth_cache_update(ARegion *region)
+static ViewDepths *view3d_depths_create(ARegion *region)
 {
-  RegionView3D *rv3d = region->regiondata;
+  ViewDepths *d = MEM_callocN(sizeof(ViewDepths), "ViewDepths");
+  d->w = region->winx;
+  d->h = region->winy;
+  d->depths = MEM_mallocN(sizeof(float) * d->w * d->h, "View depths");
 
-  /* Create storage for, and, if necessary, copy depth buffer. */
-  if (!rv3d->depths) {
-    rv3d->depths = MEM_callocN(sizeof(ViewDepths), "ViewDepths");
-  }
-  if (rv3d->depths) {
-    ViewDepths *d = rv3d->depths;
-    if (d->w != region->winx || d->h != region->winy || !d->depths) {
-      d->w = region->winx;
-      d->h = region->winy;
-      if (d->depths) {
-        MEM_freeN(d->depths);
-      }
-      d->depths = MEM_mallocN(sizeof(float) * d->w * d->h, "View depths");
-      d->damaged = true;
-    }
-
-    if (d->damaged) {
-      GPUViewport *viewport = WM_draw_region_get_viewport(region);
-      DefaultFramebufferList *fbl = GPU_viewport_framebuffer_list_get(viewport);
-      GPU_framebuffer_read_depth(fbl->depth_only_fb, 0, 0, d->w, d->h, GPU_DATA_FLOAT, d->depths);
+  {
+    GPUViewport *viewport = WM_draw_region_get_viewport(region);
+    DefaultFramebufferList *fbl = GPU_viewport_framebuffer_list_get(viewport);
+    GPU_framebuffer_read_depth(fbl->depth_only_fb, 0, 0, d->w, d->h, GPU_DATA_FLOAT, d->depths);
 
-      /* Assumed to be this as they are never changed. */
-      d->depth_range[0] = 0.0;
-      d->depth_range[1] = 1.0;
-      d->damaged = false;
-    }
+    /* Assumed to be this as they are never changed. */
+    d->depth_range[0] = 0.0;
+    d->depth_range[1] = 1.0;
   }
+  return d;
 }
 
 /* Utility function to find the closest Z value, use for auto-depth. */
@@ -2345,7 +2319,7 @@ void ED_view3d_depth_override(Depsgraph *depsgraph,
                               View3D *v3d,
                               Object *obact,
                               eV3DDepthOverrideMode mode,
-                              bool update_cache)
+                              ViewDepths **r_depths)
 {
   if (v3d->runtime.flag & V3D_RUNTIME_DEPTHBUF_OVERRIDDEN) {
     return;
@@ -2390,12 +2364,8 @@ void ED_view3d_depth_override(Depsgraph *depsgraph,
         break;
     }
 
-    if (rv3d->depths != NULL) {
-      rv3d->depths->damaged = true;
-      /* TODO: Clear cache? */
-    }
-    if (update_cache) {
-      view3d_depth_cache_update(region);
+    if (r_depths) {
+      *r_depths = view3d_depths_create(region);
     }
   }
 
@@ -2409,6 +2379,13 @@ void ED_view3d_depth_override(Depsgraph *depsgraph,
   UI_Theme_Restore(&theme_state);
 }
 
+void ED_view3d_depths_free(ViewDepths *depths)
+{
+  if (depths->depths) {
+    MEM_freeN(depths->depths);
+  }
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
diff --git a/source/blender/editors/space_view3d/view3d_edit.c b/source/blender/editors/space_view3d/view3d_edit.c
index 8b6d0e9ee04..ab0683644c3 100644
--- a/source/blender/editors/space_view3d/view3d_edit.c
+++ b/source/blender/editors/space_view3d/view3d_edit.c
@@ -953,7 +953,6 @@ static int viewrotate_modal(bContext *C, wmOperator *op, const wmEvent *event)
     }
   }
   else if (event_code == VIEW_CONFIRM) {
-    ED_view3d_depth_tag_update(vod->rv3d);
     use_autokey = true;
     ret = OPERATOR_FINISHED;
   }
@@ -1014,7 +1013,6 @@ static int viewrotate_invoke(bContext *C, wmOperator *op, const wmEvent *event)
     }
 
     viewrotate_apply(vod, event_xy);
-    ED_view3d_depth_tag_update(vod->rv3d);
 
     viewops_data_free(C, op);
 
@@ -1799,7 +1797,6 @@ static int viewmove_modal(bContext *C, wmOperator *op, const wmEvent *event)
     }
   }
   else if (event_code == VIEW_CONFIRM) {
-    ED_view3d_depth_tag_update(vod->rv3d);
     use_autokey = true;
     ret = OPERATOR_FINISHED;
   }
@@ -1840,7 +1837,6 @@ static int viewmove_invoke(bContext *C, wmOperator *op, const wmEvent *event)
   if (event->type == MOUSEPAN) {
     /* invert it, trackpad scroll follows same principle as 2d windows this way */
     viewmove_apply(vod, 2 * event->x - event->prevx, 2 * event->y - event->prevy);
-    ED_view3d_depth_tag_update(vod->rv3d);
 
     viewops_data_free(C, op);
 
@@ -2254,7 +2250,6 @@ static int viewzoom_modal(bContext *C, wmOperator *op, const wmEvent *event)
     }
   }
   else if (event_code == VIEW_CONFIRM) {
-    ED_view3d_depth_tag_update(vod->rv3d);
     use_autokey = true;
     ret = OPERATOR_FINISHED;
   }
@@ -2341,8 +2336,6 @@ static int viewzoom_exec(bContext *C, wmOperator *op)
     view3d_boxview_sync(area, region);
   }
 
-  ED_view3d_depth_tag_update(rv3d);
-
   ED_view3d_camera_lock_sync(depsgraph, v3d, rv3d);
   ED_view3d_camera_lock_autokey(v3d, rv3d, C, false, true);
 
@@ -2398,8 +2391,6 @@ static int viewzoom_invoke(bContext *C, wmOperator *op, const wmEvent *event)
                      (use_cursor_init && (U.uiflag & USER_ZOOM_TO_MOUSEPOS)));
       ED_view3d_camera_lock_autokey(vod->v3d, vod->rv3d, C, false, true);
 
-      ED_view3d_depth_tag_update(vod->rv3d);
-
       viewops_data_free(C, op);
       return OPERATOR_FINISHED;
     }
@@ -2579,7 +2570,6 @@ static int viewdolly_modal(bContext *C, wmOperator *op, const wmEvent *event)
     }
   }
   else if (event_code == VIEW_CONFIRM) {
-    ED_view3d_depth_tag_update(vod->rv3d);
     use_autokey = true;
     ret = OPERATOR_FINISHED;
   }
@@ -2636,8 +2626,6 @@ static int viewdolly_exec(bContext *C, wmOperator *op)
     view3d_boxview_sync(area, region);
   }
 
-  ED_view3d_depth_tag_update(rv3d);
-
   ED_view3d_camera_lock_sync(CTX_data_ensure_evaluated_depsgraph(C), v3d, rv3d);
 
   ED_region_tag_redraw(region);
@@ -2718,7 +2706,6 @@ static int viewdolly_invoke(bContext *C, wmOperator *op, const wmEvent *event)
                                                         event->prevx;
       }
       viewdolly_apply(vod, &event->prevx, (U.uiflag & USER_ZOOM_INVERT) == 0);
-      ED_view3d_depth_tag_update(vod->rv3d);
 
       viewops_data_free(C, op);
       return OPERATOR_FINISHED;
@@ -3629,13 +3616,13 @@ static int view3d_zoom_border_exec(bContext *C, wmOperator *op)
   ED_view3d_dist_range_get(v3d, dist_range);
 
   ED_view3d_depth_override(
-      CTX_data_ensure_evaluated_depsgraph(C), region, v3d, NULL, V3D_DEPTH_NO_GPENCIL, false);
+      CTX_data_ensure_evaluated_depsgraph(C), region, v3d, NULL, V3D_DEPTH_NO_GPENCIL, NULL);
   {
     /* avoid allocating the whole depth buffer */
     ViewDepths depth_temp = {0};
 
     /* avoid view3d_update_depths() for speed. */
-    view3d_update_depths_rect(region, &depth_temp, &rect);
+    view3d_depths_rect_create(region, &rect, &depth_temp);
 
     /* find the closest Z pixel */
     depth_close = view3d_depth_near(&depth_temp);
@@ -4433,7 +4420,6 @@ static int viewroll_modal(bContext *C, wmOperator *op, const wmEvent *event)
     }
   }
   else if (event_code == VIEW_CONFIRM) {
-    ED_view3d_depth_tag_update(vod->rv3d);
     use_autokey = true;
     ret = OPERATOR_FINISHED;
   }
@@ -4541,7 +4527,6 @@ static int viewroll_invoke(bContext *C, wmOperator *op, const wmEvent *event)
     if (event->type == MOUSEROTATE) {
       vod->init.event_xy[0] = vod->prev.event_xy[0] = event->x;
       viewroll_apply(vod, event->prevx, event->prevy);
-      ED_view3d_depth_tag_update(vod->rv3d);
 
       viewops_data_free(C, op);
       return OPERATOR_FINISHED;
@@ -4638,7 +4623,6 @@ static int viewpan_invoke(bContext *C, wmOperator *op, const wmEvent *event)
 
   viewmove_apply(vod, vod->prev.event_xy[0] + x, vod->prev.event_xy[1] + y);
 
-  ED_view3d_depth_tag_update(vod->rv3d);
   viewops_data_free(C, op);
 
   return OPERATOR_FINISHED;
diff --git a/source/blender/editors/space_view3d/view3d_intern.h b/source/blender/editors/space_view3d/view3d_intern.h
index 6f07cb8b44d..0964c2dcbcc 100644
--- a/source/blender/editors/space_view3d/view3d_intern.h
+++ b/source/blender/editors/space_view3d/view3d_intern.h
@@ -137,7 +137,7 @@ void ED_view3d_draw_depth_loop(struct Depsgraph *depsgraph,
                                struct ARegion *region,
                                View3D *v3d);
 
-void view3d_update_depths_rect(struct ARegion *region, struct ViewDepths *d, struct rcti *rect);
+void view3d_depths_rect_create(struct ARegion *region, struct rcti *rect, struct ViewDepths *r_d);
 float view3d_depth_near(struct ViewDepths *d);
 
 /* view3d_select.c */
diff --git a/source/blender/editors/space_view3d/view3d_select.c b/source/blender/editors/space_view3d/view3d_select.c
index 5bdeb2cb35f..f768d7faf63 100644
--- a/source/blender/editors/space_view3d/view3d_select.c
+++ b/source/blender/editors/space_view3d/view3d_select.c
@@ -4385,7 +4385,7 @@ static int view3d_circle_select_exec(bContext *C, wmOperator *op)
     FOREACH_OBJECT_IN_MODE_END;
   }
   else if (obact && (obact->mode & OB_MODE_PARTICLE_EDIT)) {
-    if (PE_circle_select(C, sel_op, mval, (float)radius)) {
+    if (PE_circle_select(C, wm_userdata, sel_op, mval, (float)radius)) {
       return OPERATOR_FINISHED;
     }
     return OPERATOR_CANCELLED;
diff --git a/source/blender/editors/space_view3d/view3d_utils.c b/source/blender/editors/space_view3d/view3d_utils.c
index 8ae5d4a29e9..c7da3378ae3 100644
--- a/source/blender/editors/space_view3d/view3d_utils.c
+++ b/source/blender/editors/space_view3d/view3d_utils.c
@@ -1017,9 +1017,9 @@ static float view_autodist_depth_margin(ARegion *region, const int mval[2], int
   }
 
   ViewDepths depth_temp = {0};
-  view3d_update_depths_rect(region, &depth_temp, &rect);
+  view3d_depths_rect_create(region, &rect, &depth_temp);
   float depth_close = view3d_depth_near(&depth_temp);
-  MEM_SAFE_FREE(depth_temp.depths);
+  ED_view3d_depths_free(&depth_temp);
   return depth_close;
 }
 
@@ -1044,7 +1044,7 @@ bool ED_view3d_autodist(Depsgraph *depsgraph,
   bool depth_ok = false;
 
   /* Get Z Depths, needed for perspective, nice for ortho */
-  ED_view3d_depth_override(depsgraph, region, v3d, NULL, V3D_DEPTH_NO_GPENCIL, false);
+  ED_view3d_depth_override(depsgraph, region, v3d, NULL, V3D_DEPTH_NO_GPENCIL, NULL);
 
   /* Attempt with low margin's first */
   int i = 0;
@@ -1694,7 +1694,8 @@ bool ED_view3d_depth_read_cached(const ViewDepths *vd,
   return false;
 }
 
-bool ED_view3d_depth_read_cached_normal(const ViewContext *vc,
+bool ED_view3d_depth_read_cached_normal(const ARegion *region,
+                                        const ViewDepths *depths,
                                         const int mval[2],
                                         float r_normal[3])
 {
@@ -1705,9 +1706,6 @@ bool ED_view3d_depth_read_cached_normal(const ViewContext *vc,
   bool depths_valid[9] = {false};
   float coords[9][3] = {{0}};
 
-  ARegion *region = vc->region;
-  const ViewDepths *depths = vc->rv3d->depths;
-
   for (int x = 0, i = 0; x < 2; x++) {
     for (int y = 0; y < 2; y++) {
       const int mval_ofs[2] = {mval[0] + (x - 1), mval[1] + (y - 1)};
@@ -1761,11 +1759,4 @@ bool ED_view3d_depth_unproject_v3(const ARegion *region,
   return ED_view3d_unproject_v3(region, centx, centy, depth, r_location_world);
 }
 
-void ED_view3d_depth_tag_update(RegionView3D *rv3d)
-{
-  if (rv3d->depths) {
-    rv3d->depths->damaged = true;
-  }
-}
-
 /** \} */