Merging volume embedding and transform snapping.

- Volume embed is available as a transform snap option (need new icon). Not as "continuous" as stroke embed, will have to be fixed somehow.
- Transform snaps work in armature edit mode (only snap to mesh, not other armatures, for now). Adding to other edit data type should be easy.
- Strokes can use all the transform snap options plus volume embed.

Bug fix: added small threshold to face snap (and volume embed) to prevent slipping in cracks between faces. More tweaking needed but this now takes care of all the worst cases.

2 files changed, 52 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_arithb.h b/source/blender/blenlib/BLI_arithb.h
index 6a2db92d25f..092ed00fbe5 100644
--- a/source/blender/blenlib/BLI_arithb.h
+++ b/source/blender/blenlib/BLI_arithb.h
@@ -394,6 +394,7 @@ int LineIntersectLine(float v1[3], float v2[3], float v3[3], float v4[3], float
 int LineIntersectLineStrict(float v1[3], float v2[3], float v3[3], float v4[3], float vi[3], float *lambda);
 int LineIntersectsTriangle(float p1[3], float p2[3], float v0[3], float v1[3], float v2[3], float *lambda, float *uv);
 int RayIntersectsTriangle(float p1[3], float d[3], float v0[3], float v1[3], float v2[3], float *lambda, float *uv);
+int RayIntersectsTriangleThreshold(float p1[3], float d[3], float v0[3], float v1[3], float v2[3], float *lambda, float *uv, float threshold);
 int SweepingSphereIntersectsTriangleUV(float p1[3], float p2[3], float radius, float v0[3], float v1[3], float v2[3], float *lambda, float *ipoint);
 int AxialLineIntersectsTriangle(int axis, float co1[3], float co2[3], float v0[3], float v1[3], float v2[3], float *lambda);
 int AabbIntersectAabb(float min1[3], float max1[3], float min2[3], float max2[3]);
diff --git a/source/blender/blenlib/intern/arithb.c b/source/blender/blenlib/intern/arithb.c
index 5f94df6f5eb..ad1dc1ca12c 100644
--- a/source/blender/blenlib/intern/arithb.c
+++ b/source/blender/blenlib/intern/arithb.c
@@ -3896,6 +3896,57 @@ int RayIntersectsTriangle(float p1[3], float d[3], float v0[3], float v1[3], flo
 	return 1;
 }
 
+int RayIntersectsTriangleThreshold(float p1[3], float d[3], float v0[3], float v1[3], float v2[3], float *lambda, float *uv, float threshold)
+{
+	float p[3], s[3], e1[3], e2[3], q[3];
+	float a, f, u, v;
+	float du = 0, dv = 0;
+	
+	VecSubf(e1, v1, v0);
+	VecSubf(e2, v2, v0);
+	
+	Crossf(p, d, e2);
+	a = Inpf(e1, p);
+	if ((a > -0.000001) && (a < 0.000001)) return 0;
+	f = 1.0f/a;
+	
+	VecSubf(s, p1, v0);
+	
+	Crossf(q, s, e1);
+	*lambda = f * Inpf(e2, q);
+	if ((*lambda < 0.0)) return 0;
+	
+	u = f * Inpf(s, p);
+	v = f * Inpf(d, q);
+	
+	if (u < 0) du = u;
+	if (u > 1) du = u - 1;
+	if (v < 0) dv = v;
+	if (v > 1) dv = v - 1;
+	if (u > 0 && v > 0 && u + v > 1)
+	{
+		float t = u + v - 1;
+		du = u - t/2;
+		dv = v - t/2;
+	}
+
+	VecMulf(e1, du);
+	VecMulf(e2, dv);
+	
+	if (Inpf(e1, e1) + Inpf(e2, e2) > threshold * threshold)
+	{
+		return 0;
+	}
+
+	if(uv) {
+		uv[0]= u;
+		uv[1]= v;
+	}
+	
+	return 1;
+}
+
+
 /* Adapted from the paper by Kasper Fauerby */
 /* "Improved Collision detection and Response" */
 static int getLowestRoot(float a, float b, float c, float maxR, float* root)