Transform: improve normal orientation

- when 3 verts are selected ensure the normal is flipped on the side of existing vert normals.
  also use the most distant 2 verts to define the tangent.

- when 2 vertices are selected, the normal wasn't aligned with the vert normal.

1 files changed, 9 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_utildefines.h b/source/blender/blenlib/BLI_utildefines.h
index 9bf720c03ea..0f7c0ac0fd8 100644
--- a/source/blender/blenlib/BLI_utildefines.h
+++ b/source/blender/blenlib/BLI_utildefines.h
@@ -56,6 +56,15 @@
 #define MAX3(x, y, z)       (MAX2(MAX2((x), (y)), (z)))
 #define MAX4(x, y, z, a)    (MAX2(MAX2((x), (y)), MAX2((z), (a))))
 
+/* min/max that return a value of our choice */
+#define MAX3_PAIR(cmp_a, cmp_b, cmp_c, ret_a, ret_b, ret_c) \
+	((cmp_a > cmp_b) ? ((cmp_a > cmp_c) ? ret_a : ret_c) : \
+	                   ((cmp_b > cmp_c) ? ret_b : ret_c))
+
+#define MIN3_PAIR(cmp_a, cmp_b, cmp_c, ret_a, ret_b, ret_c) \
+	((cmp_a < cmp_b) ? ((cmp_a < cmp_c) ? ret_a : ret_c) : \
+	                   ((cmp_b < cmp_c) ? ret_b : ret_c))
+
 #define INIT_MINMAX(min, max) {                                               \
 		(min)[0] = (min)[1] = (min)[2] =  1.0e30f;                            \
 		(max)[0] = (max)[1] = (max)[2] = -1.0e30f;                            \