Fix #30638 and part of #30646.

Problem was that area calculation of polygons was done relative to the xy plane, and with a very obscure (to me at least) algorithm. That meant that vertical ngons would get 0 area. 

Commented initial code in case this is a strange optimization case that someone wants to use and used a cleaner algorithm: first project vertices to the ngon plane, defined by the normal of the ngon and the center (mean) of the ngon vertices. This will only be exact for convex and mostly planar ngons, still it is much better than the previous code.

Also fixed memory leak when stretch display was on.

1 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/math_vector.c b/source/blender/blenlib/intern/math_vector.c
index ce387291dff..e7c96ce3dc3 100644
--- a/source/blender/blenlib/intern/math_vector.c
+++ b/source/blender/blenlib/intern/math_vector.c
@@ -286,6 +286,20 @@ void project_v3_v3v3(float c[3], const float v1[3], const float v2[3])
 	c[2] = mul * v2[2];
 }
 
+/* project a vector on a plane defined by normal and a plane point p */
+void project_v3_plane(float v[3], const float n[3], const float p[3])
+{
+	float vector[3];
+	float mul;
+
+	sub_v3_v3v3(vector, v, p);
+	mul = dot_v3v3(vector, n)/len_squared_v3(n);
+
+	mul_v3_v3fl(vector, n, mul);
+
+	sub_v3_v3(v, vector);
+}
+
 /* Returns a vector bisecting the angle at v2 formed by v1, v2 and v3 */
 void bisect_v3_v3v3v3(float out[3], const float v1[3], const float v2[3], const float v3[3])
 {