Skeleton Sketching

Cut gesture: drawing a line with RMB adds exact points (joints in the final skeleton) on strokes. Can cut multiple strokes at once as long as it cuts each one only once (this could be changed).

Shape of the gesture doesn't matter, but eventually it would be straight lines shapes for cuts.

source/blender/blenlib/intern/arithb.c

@@ -4221,6 +4221,67 @@ int LineIntersectLine(float v1[3], float v2[3], float v3[3], float v4[3], float
 	}
 } 
 
+/* Intersection point strictly between the two lines
+ * 0 when no intersection is found 
+ * */
+int LineIntersectLineStrict(float v1[3], float v2[3], float v3[3], float v4[3], float vi[3], float *lambda)
+{
+	float a[3], b[3], c[3], ab[3], cb[3], ca[3], dir1[3], dir2[3];
+	float d;
+	float d1;
+	
+	VecSubf(c, v3, v1);
+	VecSubf(a, v2, v1);
+	VecSubf(b, v4, v3);
+
+	VecCopyf(dir1, a);
+	Normalize(dir1);
+	VecCopyf(dir2, b);
+	Normalize(dir2);
+	d = Inpf(dir1, dir2);
+	if (d == 1.0f || d == -1.0f || d == 0) {
+		/* colinear or one vector is zero-length*/
+		return 0;
+	}
+	
+	d1 = d;
+
+	Crossf(ab, a, b);
+	d = Inpf(c, ab);
+
+	/* test if the two lines are coplanar */
+	if (d > -0.000001f && d < 0.000001f) {
+		float f1, f2;
+		Crossf(cb, c, b);
+		Crossf(ca, c, a);
+
+		f1 = Inpf(cb, ab) / Inpf(ab, ab);
+		f2 = Inpf(ca, ab) / Inpf(ab, ab);
+		
+		if (f1 >= 0 && f1 <= 1 &&
+			f2 >= 0 && f2 <= 1)
+		{
+			VecMulf(a, f1);
+			VecAddf(vi, v1, a);
+			
+			if (lambda != NULL)
+			{
+				*lambda = f1;
+			}
+			
+			return 1; /* intersection found */
+		}
+		else
+		{
+			return 0;
+		}
+	}
+	else
+	{
+		return 0;
+	}
+} 
+
 int AabbIntersectAabb(float min1[3], float max1[3], float min2[3], float max2[3])
 {
 	return (min1[0]<max2[0] && min1[1]<max2[1] && min1[2]<max2[2] &&