fix for own bad logic with polygon normal calculation, was reading one past the loop array (reported as bug #31431).

1 files changed, 16 insertions, 10 deletions

diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index 944f06cf740..16e75fff702 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -2771,16 +2771,19 @@ static void mesh_calc_ngon_normal(MPoly *mpoly, MLoop *loopstart,
 {
 	const int nverts = mpoly->totloop;
 	float const *v_prev = mvert[loopstart[nverts - 1].v].co;
-	float const *v_curr = mvert[loopstart->v].co;
-	float n[3] = {0.0f};
+	float const *v_curr;
 	int i;
 
+	zero_v3(normal);
+
 	/* Newell's Method */
-	for (i = 0; i < nverts; v_prev = v_curr, v_curr = mvert[loopstart[++i].v].co) {
-		add_newell_cross_v3_v3v3(n, v_prev, v_curr);
+	for (i = 0; i < nverts; i++) {
+		v_curr = mvert[loopstart[i].v].co;
+		add_newell_cross_v3_v3v3(normal, v_prev, v_curr);
+		v_prev = v_curr;
 	}
 
-	if (UNLIKELY(normalize_v3_v3(normal, n) == 0.0f)) {
+	if (UNLIKELY(normalize_v3(normal) == 0.0f)) {
 		normal[2] = 1.0f; /* other axis set to 0.0 */
 	}
 }
@@ -2818,16 +2821,19 @@ static void mesh_calc_ngon_normal_coords(MPoly *mpoly, MLoop *loopstart,
 {
 	const int nverts = mpoly->totloop;
 	float const *v_prev = vertex_coords[loopstart[nverts - 1].v];
-	float const *v_curr = vertex_coords[loopstart->v];
-	float n[3] = {0.0f};
+	float const *v_curr;
 	int i;
 
+	zero_v3(normal);
+
 	/* Newell's Method */
-	for (i = 0; i < nverts; v_prev = v_curr, v_curr = vertex_coords[loopstart[++i].v]) {
-		add_newell_cross_v3_v3v3(n, v_prev, v_curr);
+	for (i = 0; i < nverts; i++) {
+		v_curr = vertex_coords[loopstart[i].v];
+		add_newell_cross_v3_v3v3(normal, v_prev, v_curr);
+		v_prev = v_curr;
 	}
 
-	if (UNLIKELY(normalize_v3_v3(normal, n) == 0.0f)) {
+	if (UNLIKELY(normalize_v3(normal) == 0.0f)) {
 		normal[2] = 1.0f; /* other axis set to 0.0 */
 	}
 }