Texture Paint: prevent normal angle masking duplicating backface culling.

If backface culling is off, the user obviously wants to paint on
back faces, so the normal angle cutoff designed to prevent painting
at glancing angles shouldn't do the culling as a side effect.

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/editors/sculpt_paint/paint_image_proj.c b/source/blender/editors/sculpt_paint/paint_image_proj.c
index 6ef4a230a57..f3af52f4f47 100644
--- a/source/blender/editors/sculpt_paint/paint_image_proj.c
+++ b/source/blender/editors/sculpt_paint/paint_image_proj.c
@@ -1461,6 +1461,11 @@ static float project_paint_uvpixel_mask(
 			angle_cos = dot_v3v3(viewDirPersp, no);
 		}
 
+		/* If backface culling is disabled, allow painting on back faces. */
+		if (!ps->do_backfacecull) {
+			angle_cos = fabsf(angle_cos);
+		}
+
 		if (angle_cos <= ps->normal_angle__cos) {
 			return 0.0f; /* outsize the normal limit*/
 		}