From 9547b76c2e8e0f6aa07858e94e4f0c404b86ac7d Mon Sep 17 00:00:00 2001
From: Jason Hays <jason_hays22@mymail.eku.edu>
Date: Thu, 31 May 2012 17:22:52 +0000
Subject: This fixes a precision issue in multi-paint so that near zero values
 do not cause flickering as you paint.

It also changes multi-paint's "zero weight color" to black again--it was unintentionally changed to red some time late last year when an aspect of the colors were changed.
---
 source/blender/blenkernel/intern/DerivedMesh.c     | 4 ++--
 source/blender/editors/sculpt_paint/paint_vertex.c | 8 +++++---
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/source/blender/blenkernel/intern/DerivedMesh.c b/source/blender/blenkernel/intern/DerivedMesh.c
index 5774dd7b1ba..7130776d05a 100644
--- a/source/blender/blenkernel/intern/DerivedMesh.c
+++ b/source/blender/blenkernel/intern/DerivedMesh.c
@@ -1054,10 +1054,10 @@ static void calc_weightpaint_vert_color(
 	}
 
 	if (make_black) { /* TODO, theme color */
-		r_col[3] = 0;
+		r_col[3] = 255;
 		r_col[2] = 0;
 		r_col[1] = 0;
-		r_col[0] = 255;
+		r_col[0] = 0;
 	}
 	else {
 		CLAMP(input, 0.0f, 1.0f);
diff --git a/source/blender/editors/sculpt_paint/paint_vertex.c b/source/blender/editors/sculpt_paint/paint_vertex.c
index e05191dad3b..88cf9b1b0dd 100644
--- a/source/blender/editors/sculpt_paint/paint_vertex.c
+++ b/source/blender/editors/sculpt_paint/paint_vertex.c
@@ -1878,6 +1878,7 @@ static void do_weight_paint_vertex(
 		float oldw;
 		float neww;
 		float testw = 0;
+		float observedChange = 0;
 		float change = 0;
 		float oldChange = 0;
 		int i;
@@ -1889,13 +1890,14 @@ static void do_weight_paint_vertex(
 		                    wpi->brush_alpha_value, wpi->do_flip, do_multipaint_totsel);
 		
 		/* setup multi-paint */
-		if (do_multipaint_totsel) {
+		observedChange = neww - oldw;
+		if (do_multipaint_totsel && observedChange) {
 			dv_copy.dw = MEM_dupallocN(dv->dw);
 			dv_copy.flag = dv->flag;
 			dv_copy.totweight = dv->totweight;
 			tdw = dw;
 			tdw_prev = dw_prev;
-			change = get_mp_change(&wp->wpaint_prev[index], wpi->defbase_tot, wpi->defbase_sel, neww - oldw);
+			change = get_mp_change(&wp->wpaint_prev[index], wpi->defbase_tot, wpi->defbase_sel, observedChange);
 			if (change) {
 				if (!tdw->weight) {
 					i = get_first_selected_nonzero_weight(dv, wpi->defbase_tot, wpi->defbase_sel);
@@ -1911,7 +1913,7 @@ static void do_weight_paint_vertex(
 					if (tdw->weight != tdw_prev->weight) {
 						oldChange = tdw->weight / tdw_prev->weight;
 						testw = tdw_prev->weight * change;
-						if (testw > tdw_prev->weight) {
+						if (observedChange > 0) {
 							if (change > oldChange) {
 								/* reset the weights and use the new change */
 								defvert_reset_to_prev(wp->wpaint_prev + index, dv);
-- 
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