Fix #26932: When I enable multires, and start sculpting, some parts of the mesh just disappears.

Redraw issue was caused due to different redraw rectangles used for 3d view redraw and
gathering PBVH nodes to be re-drawed. I moved redraw rect expansion with rect from
previous step into sculpt_get_redraw_rect, so now redrawing works as it was planned
some commits ago -- redraw everything to which is inside currect rectangle and rectangle
from previous stroke step -- this still prevents artifact caused by fast strokes but
mesh doesn't disappear.

Brecht, Nicholas: it's the simpliest fix i could suggest atm. I've got some more
ideas with additional node flags, but it looked more complicated for me and
made code more difficult to understand. If you could see something better (like
revert all this redraw fixes for fast strokes) please tell me.

1 files changed, 20 insertions, 10 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 1543cbedae9..ad1d55c336b 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -306,7 +306,23 @@ static int sculpt_get_redraw_rect(ARegion *ar, RegionView3D *rv3d,
 		}
 	}
 	
-	return rect->xmin < rect->xmax && rect->ymin < rect->ymax;
+	if (rect->xmin < rect->xmax && rect->ymin < rect->ymax) {
+		/* expand redraw rect with redraw rect from previous step to prevent
+		   partial-redraw issues caused by fast strokes. This is needed here (not in sculpt_flush_update)
+		   as it was before because redraw rectangle should be the same in both of
+		   optimized PBVH draw function and 3d view redraw (if not -- some mesh parts could
+		   disapper from screen (sergey) */
+		SculptSession *ss = ob->sculpt;
+
+		if (ss->cache) {
+			if (!BLI_rcti_is_empty(&ss->cache->previous_r))
+				BLI_union_rcti(rect, &ss->cache->previous_r);
+		}
+
+		return 1;
+	}
+
+	return 0;
 }
 
 void sculpt_get_redraw_planes(float planes[4][4], ARegion *ar,
@@ -3417,20 +3433,14 @@ static void sculpt_flush_update(bContext *C)
 
 		BLI_pbvh_update(ss->pbvh, PBVH_UpdateBB, NULL);
 		if (sculpt_get_redraw_rect(ar, CTX_wm_region_view3d(C), ob, &r)) {
+			if (ss->cache)
+				ss->cache->previous_r= r;
+
 			r.xmin += ar->winrct.xmin + 1;
 			r.xmax += ar->winrct.xmin - 1;
 			r.ymin += ar->winrct.ymin + 1;
 			r.ymax += ar->winrct.ymin - 1;
 
-			if (ss->cache) {
-				rcti tmp = r;
-
-				if (!BLI_rcti_is_empty(&ss->cache->previous_r))
-					BLI_union_rcti(&r, &ss->cache->previous_r);
-
-				ss->cache->previous_r= tmp;
-			}
-
 			ss->partial_redraw = 1;
 			ED_region_tag_redraw_partial(ar, &r);
 		}