fix for edge slide bug, when there were no edges to slide along the direction calculated from the face would be wrong half the time (depending on the edge loop direction which is arbitrary).

1 files changed, 15 insertions, 7 deletions

diff --git a/source/blender/editors/transform/transform.c b/source/blender/editors/transform/transform.c
index 6f811de3c8c..62b57aa071b 100644
--- a/source/blender/editors/transform/transform.c
+++ b/source/blender/editors/transform/transform.c
@@ -4901,16 +4901,24 @@ static BMLoop *get_next_loop(BMVert *v, BMLoop *l,
 				mul_v3_fl(a, 1.0f / (float)i);
 			}
 			else {
-				float f1[3], f2[3], f3[3];
+				/* When there is no edge to slide along,
+				 * we must slide along the vector defined by the face we're attach to */
+				float e_dir_prev[3], e_dir_next[3], tvec[3];
 
-				sub_v3_v3v3(f1, BM_edge_other_vert(e_prev, v)->co, v->co);
-				sub_v3_v3v3(f2, BM_edge_other_vert(e_next, v)->co, v->co);
+				sub_v3_v3v3(e_dir_prev, BM_edge_other_vert(e_prev, v)->co, v->co);
+				sub_v3_v3v3(e_dir_next, BM_edge_other_vert(e_next, v)->co, v->co);
 
-				cross_v3_v3v3(f3, f1, l->f->no);
-				cross_v3_v3v3(a, f2, l->f->no);
-				negate_v3(a);
+				cross_v3_v3v3(tvec, l->f->no, e_dir_prev);
+				cross_v3_v3v3(a, e_dir_next, l->f->no);
 
-				mid_v3_v3v3(a, a, f3);
+				mid_v3_v3v3(a, a, tvec);
+
+				/* check if we need to flip
+				 * (compare the normal defines by the edges with the face normal) */
+				cross_v3_v3v3(tvec, e_dir_prev, e_dir_next);
+				if (dot_v3v3(tvec, l->f->no) > 0.0f) {
+					negate_v3(a);
+				}
 			}
 
 			copy_v3_v3(vec, a);