Bugfix for incorrect unwrapping of some triangle shaped quads;

Triangulation of these quads could lead to degenerate triangles, resulting
in UV's in random places. Now quads are automatically triangulated in the
best direction.

This bug was reported by Tim Fisher (thanks!).

1 files changed, 151 insertions, 38 deletions

diff --git a/source/blender/src/unwrapper.c b/source/blender/src/unwrapper.c
index 4337c586650..a0d96cebb9a 100644
--- a/source/blender/src/unwrapper.c
+++ b/source/blender/src/unwrapper.c
@@ -364,19 +364,35 @@ static void lscm_add_triangle(float *v1, float *v2, float *v3, int vid1, int vid
 	nlEnd(NL_ROW);
 }
 
+static float lscm_angle_cos(float *v1, float *v2, float *v3)
+{
+    float vec1[3], vec2[3];
+
+	VecSubf(vec1, v2, v1);
+	VecSubf(vec2, v3, v1);
+	Normalise(vec1);
+	Normalise(vec2);
+
+	return vec1[0]*vec2[0] + vec1[1]*vec2[1] + vec1[2]*vec2[2];
+}
+
 static int lscm_build_vertex_data(Mesh *me, int *groups, int gid, LscmVert **lscm_vertices, LscmVert ***sort_vertices)
 {
+	MVert *mv;
 	MFace *mf;
 	TFace *tf;
 	int *gf, totvert, a;
 	LscmVert *lscmvert, **sortvert;
 	LscmVert *v1, *v2, *v3, **sv1, **sv2, **sv3;
+	float a1, a2;
 
 	/* determine size for malloc */
 	totvert= 0;
+	mv = me->mvert;
 	mf= me->mface;
 	tf= me->tface;
 	gf= groups;
+	a1 = a2 = 0;
 
 	for(a=me->totface; a>0; a--) {
 		if(*gf==gid) {
@@ -408,50 +424,66 @@ static int lscm_build_vertex_data(Mesh *me, int *groups, int gid, LscmVert **lsc
 	/* warning: ugly code :) */
 	for(a=me->totface; a>0; a--) {
 		if(*gf==gid) {
-			v1->v= mf->v1;
-			v2->v= mf->v2;
-			v3->v= mf->v3;
+			/* determine triangulation direction, to avoid degenerate
+			   triangles (small cos = degenerate). */
+			if(mf->v4) {
+				a1 = lscm_angle_cos((mv+mf->v1)->co, (mv+mf->v2)->co, (mv+mf->v3)->co);
+				a1 += lscm_angle_cos((mv+mf->v2)->co, (mv+mf->v1)->co, (mv+mf->v3)->co);
+				a1 += lscm_angle_cos((mv+mf->v3)->co, (mv+mf->v1)->co, (mv+mf->v2)->co);
 
-			v1->tf_index= 0;
-			v2->tf_index= 1;
-			v3->tf_index= 2;
+				a2 = lscm_angle_cos((mv+mf->v1)->co, (mv+mf->v2)->co, (mv+mf->v4)->co);
+				a2 += lscm_angle_cos((mv+mf->v2)->co, (mv+mf->v1)->co, (mv+mf->v4)->co);
+				a2 += lscm_angle_cos((mv+mf->v4)->co, (mv+mf->v1)->co, (mv+mf->v2)->co);
+			}
 
-			v1->flag= v2->flag= v3->flag= 0;
+			a1 = 0.0; a2 = 1.0;
 
-			v1->v1= mf->v2;
-			v1->v2= mf->v3;
+			if(!mf->v4 || a1 > a2) {
+				v1->v= mf->v1;
+				v2->v= mf->v2;
+				v3->v= mf->v3;
 
-			v2->v1= mf->v1;
-			v2->v2= mf->v3;
+				v1->tf_index= 0;
+				v2->tf_index= 1;
+				v3->tf_index= 2;
 
-			v3->v1= mf->v1;
-			v3->v2= mf->v2;
+				v1->flag= v2->flag= v3->flag= 0;
 
-			v1->tf= v2->tf= v3->tf= tf;
+				v1->v1= v2->v;
+				v1->v2= v3->v;
 
-			*sv1= v1;
-			*sv2= v2;
-			*sv3= v3;
+				v2->v1= v1->v;
+				v2->v2= v3->v;
 
-			if(tf->unwrap & TF_SEAM1) {
-				v1->flag |= LSCM_SEAM1;
-				v2->flag |= LSCM_SEAM1;
-			}
+				v3->v1= v1->v;
+				v3->v2= v2->v;
 
-			if(tf->unwrap & TF_SEAM2) {
-				v2->flag |= LSCM_SEAM2;
-				v3->flag |= LSCM_SEAM2;
-			}
+				v1->tf= v2->tf= v3->tf= tf;
 
-			if(!mf->v4 && tf->unwrap & TF_SEAM3) {
-				v1->flag |= LSCM_SEAM2;
-				v3->flag |= LSCM_SEAM1;
-			}
+				*sv1= v1;
+				*sv2= v2;
+				*sv3= v3;
 
-			v1 += 3; v2 += 3; v3 += 3;
-			sv1 += 3; sv2 += 3; sv3 += 3;
+				if(tf->unwrap & TF_SEAM1) {
+					v1->flag |= LSCM_SEAM1;
+					v2->flag |= LSCM_SEAM1;
+				}
+	
+				if(tf->unwrap & TF_SEAM2) {
+					v2->flag |= LSCM_SEAM2;
+					v3->flag |= LSCM_SEAM2;
+				}
 
-			if(mf->v4) {
+				if(!mf->v4 && tf->unwrap & TF_SEAM3) {
+					v1->flag |= LSCM_SEAM2;
+					v3->flag |= LSCM_SEAM1;
+				}
+
+				v1 += 3; v2 += 3; v3 += 3;
+				sv1 += 3; sv2 += 3; sv3 += 3;
+			}
+
+			if(mf->v4 && a1 > a2) {
 				v1->v= mf->v1;
 				v2->v= mf->v3;
 				v3->v= mf->v4;
@@ -462,14 +494,14 @@ static int lscm_build_vertex_data(Mesh *me, int *groups, int gid, LscmVert **lsc
 
 				v1->flag= v2->flag= v3->flag= 0;
 
-				v1->v1= mf->v3;
-				v1->v2= mf->v4;
+				v1->v1= v2->v;
+				v1->v2= v3->v;
 
-				v2->v1= mf->v4;
-				v2->v2= mf->v1;
+				v2->v1= v3->v;
+				v2->v2= v1->v;
 	
-				v3->v1= mf->v1;
-				v3->v2= mf->v3;
+				v3->v1= v1->v;
+				v3->v2= v2->v;
 
 				v1->tf= v2->tf= v3->tf= tf;
 
@@ -490,6 +522,87 @@ static int lscm_build_vertex_data(Mesh *me, int *groups, int gid, LscmVert **lsc
 				v1 += 3; v2 += 3; v3 += 3;
 				sv1 += 3; sv2 += 3; sv3 += 3;
 			}
+
+			if(mf->v4 && a1 <= a2) {
+				v1->v= mf->v1;
+				v2->v= mf->v2;
+				v3->v= mf->v4;
+
+				v1->tf_index= 0;
+				v2->tf_index= 1;
+				v3->tf_index= 3;
+
+				v1->flag= v2->flag= v3->flag= 0;
+
+				v1->v1= v2->v;
+				v1->v2= v3->v;
+
+				v2->v1= v1->v;
+				v2->v2= v3->v;
+
+				v3->v1= v1->v;
+				v3->v2= v2->v;
+
+				v1->tf= v2->tf= v3->tf= tf;
+
+				*sv1= v1;
+				*sv2= v2;
+				*sv3= v3;
+
+				if(tf->unwrap & TF_SEAM1) {
+					v1->flag |= LSCM_SEAM1;
+					v2->flag |= LSCM_SEAM1;
+				}
+	
+				if(tf->unwrap & TF_SEAM4) {
+					v1->flag |= LSCM_SEAM2;
+					v3->flag |= LSCM_SEAM1;
+				}
+
+				v1 += 3; v2 += 3; v3 += 3;
+				sv1 += 3; sv2 += 3; sv3 += 3;
+
+				/* -- */
+
+				v1->v= mf->v2;
+				v2->v= mf->v3;
+				v3->v= mf->v4;
+
+				v1->tf_index= 1;
+				v2->tf_index= 2;
+				v3->tf_index= 3;
+
+				v1->flag= v2->flag= v3->flag= 0;
+
+				v1->v1= v2->v;
+				v1->v2= v3->v;
+
+				v2->v1= v1->v;
+				v2->v2= v3->v;
+	
+				v3->v1= v1->v;
+				v3->v2= v2->v;
+
+				v1->tf= v2->tf= v3->tf= tf;
+
+				*sv1= v1;
+				*sv2= v2;
+				*sv3= v3;
+
+				if(tf->unwrap & TF_SEAM2) {
+					v1->flag |= LSCM_SEAM1;
+					v2->flag |= LSCM_SEAM1;
+				}
+	
+				if(tf->unwrap & TF_SEAM3) {
+					v2->flag |= LSCM_SEAM2;
+					v3->flag |= LSCM_SEAM2;
+				}
+
+				v1 += 3; v2 += 3; v3 += 3;
+				sv1 += 3; sv2 += 3; sv3 += 3;
+			}
+
 		}
 		tf++; mf++; gf++;
 	}