Old bug fix: Uv smart stitch failed to detect angle if islands were

rotated close to 180 degrees and there were edges both below and above
the 180 degree threshhold. Separating and averaging the negative and
positive angles seems to solve the issue making the tool a bit more
robust ;)

source/blender/blenlib/BLI_math_matrix.h

@@ -88,6 +88,7 @@ void mul_serie_m4(float R[4][4],
 
 void mul_m4_v3(float M[4][4], float r[3]);
 void mul_v3_m4v3(float r[3], float M[4][4], const float v[3]);
+void mul_v2_m2v2(float r[2], float M[2][2], const float v[2]);
 void mul_mat3_m4_v3(float M[4][4], float r[3]);
 void mul_m4_v4(float M[4][4], float r[4]);
 void mul_v4_m4v4(float r[4], float M[4][4], const float v[4]);
@@ -170,6 +171,7 @@ void mat4_to_size(float r[3], float M[4][4]);
 
 void translate_m4(float mat[4][4], float tx, float ty, float tz);
 void rotate_m4(float mat[4][4], const char axis, const float angle);
+void rotate_m2(float mat[2][2], const float angle);
 
 
 void mat3_to_rot_size(float rot[3][3], float size[3], float mat3[3][3]);

source/blender/blenlib/intern/math_matrix.c

@@ -344,6 +344,12 @@ void mul_v3_m4v3(float in[3], float mat[4][4], const float vec[3])
 	in[2] = x * mat[0][2] + y * mat[1][2] + mat[2][2] * vec[2] + mat[3][2];
 }
 
+void mul_v2_m2v2(float r[2], float M[2][2], const float v[2])
+{
+	r[0] = M[0][0]*v[0] + M[1][0]*v[1];
+	r[1] = M[0][1]*v[0] + M[1][1]*v[1];
+}
+
 /* same as mul_m4_v3() but doesnt apply translation component */
 void mul_mat3_m4_v3(float mat[4][4], float vec[3])
 {
@@ -1304,6 +1310,13 @@ void rotate_m4(float mat[4][4], const char axis, const float angle)
 	}
 }
 
+void rotate_m2(float mat[2][2], const float angle)
+{
+	mat[0][0] = mat[1][1] = cosf(angle);
+	mat[0][1] = sinf(angle);
+	mat[1][0] = -mat[0][1];
+}
+
 void blend_m3_m3m3(float out[3][3], float dst[3][3], float src[3][3], const float srcweight)
 {
 	float srot[3][3], drot[3][3];

source/blender/editors/uvedit/uvedit_smart_stitch.c

@@ -100,11 +100,13 @@ struct IslandStitchData;
 typedef struct IslandStitchData {
 	/* rotation can be used only for edges, for vertices there is no such notion */
 	float rotation;
+	float rotation_neg;
 	float translation[2];
 	/* Used for rotation, the island will rotate around this point */
 	float medianPoint[2];
 	int numOfElements;
 	int num_rot_elements;
+	int num_rot_elements_neg;
 	/* flag to remember if island has been added for preview */
 	char addedForPreview;
 	/* flag an island to be considered for determining static island */
@@ -286,20 +288,15 @@ static int getNumOfIslandUvs(UvElementMap *elementMap, int island)
 	}
 }
 
-static void stitch_uv_rotate(float rotation, float medianPoint[2], float uv[2], float aspect)
+static void stitch_uv_rotate(float mat[2][2], float medianPoint[2], float uv[2], float aspect)
 {
 	float uv_rotation_result[2];
 
 	uv[1] /= aspect;
 
-	uv[0] -= medianPoint[0];
-	uv[1] -= medianPoint[1];
-
-	uv_rotation_result[0] = cosf(rotation) * uv[0] - sinf(rotation) * uv[1];
-	uv_rotation_result[1] = sinf(rotation) * uv[0] + cosf(rotation) * uv[1];
-
-	uv[0] = uv_rotation_result[0] + medianPoint[0];
-	uv[1] = uv_rotation_result[1] + medianPoint[1];
+	sub_v2_v2(uv, medianPoint);
+	mul_v2_m2v2(uv_rotation_result, mat, uv);
+	add_v2_v2v2(uv, uv_rotation_result, medianPoint);
 
 	uv[1] *= aspect;
 }
@@ -412,17 +409,35 @@ static void stitch_calculate_island_snapping(StitchState *state, PreviewPosition
 	for (i = 0; i < state->element_map->totalIslands; i++) {
 		if (island_stitch_data[i].addedForPreview) {
 			int numOfIslandUVs = 0, j;
+			int totelem = island_stitch_data[i].num_rot_elements_neg + island_stitch_data[i].num_rot_elements;
+			float rotation;
+			float rotation_mat[2][2];
 
 			/* check to avoid divide by 0 */
-			if (island_stitch_data[i].num_rot_elements > 0) {
+			if (island_stitch_data[i].num_rot_elements > 1)
 				island_stitch_data[i].rotation /= island_stitch_data[i].num_rot_elements;
+
+			if (island_stitch_data[i].num_rot_elements_neg > 1)
+				island_stitch_data[i].rotation_neg /= island_stitch_data[i].num_rot_elements_neg;
+
+			if (island_stitch_data[i].numOfElements > 1) {
 				island_stitch_data[i].medianPoint[0] /= island_stitch_data[i].numOfElements;
 				island_stitch_data[i].medianPoint[1] /= island_stitch_data[i].numOfElements;
-				island_stitch_data[i].medianPoint[1] /= state->aspect;
-			}
-			island_stitch_data[i].translation[0] /= island_stitch_data[i].numOfElements;
-			island_stitch_data[i].translation[1] /= island_stitch_data[i].numOfElements;
 
+				island_stitch_data[i].translation[0] /= island_stitch_data[i].numOfElements;
+				island_stitch_data[i].translation[1] /= island_stitch_data[i].numOfElements;
+			}
+
+			island_stitch_data[i].medianPoint[1] /= state->aspect;
+			if ((island_stitch_data[i].rotation + island_stitch_data[i].rotation_neg < M_PI_2) ||
+				island_stitch_data[i].num_rot_elements == 0 || island_stitch_data[i].num_rot_elements_neg == 0)
+				rotation = (island_stitch_data[i].rotation*island_stitch_data[i].num_rot_elements -
+							island_stitch_data[i].rotation_neg*island_stitch_data[i].num_rot_elements_neg)/totelem;
+			else
+				rotation = (island_stitch_data[i].rotation*island_stitch_data[i].num_rot_elements +
+							(2*M_PI - island_stitch_data[i].rotation_neg)*island_stitch_data[i].num_rot_elements_neg)/totelem;
+
+			rotate_m2(rotation_mat, rotation);
 			numOfIslandUVs = getNumOfIslandUvs(state->element_map, i);
 			element = &state->element_map->buf[state->element_map->islandIndices[i]];
 			for (j = 0; j < numOfIslandUVs; j++, element++) {
@@ -436,15 +451,16 @@ static void stitch_calculate_island_snapping(StitchState *state, PreviewPosition
 
 					if (final) {
 
-						stitch_uv_rotate(island_stitch_data[i].rotation, island_stitch_data[i].medianPoint, luv->uv, state->aspect);
+						stitch_uv_rotate(rotation_mat, island_stitch_data[i].medianPoint, luv->uv, state->aspect);
 
 						add_v2_v2(luv->uv, island_stitch_data[i].translation);
 					}
 
 					else {
+
 						int face_preview_pos = preview_position[BM_elem_index_get(element->l->f)].data_position;
 
-						stitch_uv_rotate(island_stitch_data[i].rotation, island_stitch_data[i].medianPoint,
+						stitch_uv_rotate(rotation_mat, island_stitch_data[i].medianPoint,
 						                 preview->preview_polys + face_preview_pos + 2 * element->tfindex, state->aspect);
 
 						add_v2_v2(preview->preview_polys + face_preview_pos + 2 * element->tfindex,
@@ -500,13 +516,15 @@ static void stitch_island_calculate_edge_rotation(UvEdge *edge, StitchState *sta
 
 	edgecos = dot_v2v2(uv1, uv2);
 	edgesin = cross_v2v2(uv1, uv2);
+	rotation = acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
 
-	rotation = (edgesin > 0.0f) ?
-	            +acosf(max_ff(-1.0f, min_ff(1.0f, edgecos))) :
-	            -acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
-
-	island_stitch_data[element1->island].num_rot_elements++;
-	island_stitch_data[element1->island].rotation += rotation;
+	if (edgesin > 0.0f) {
+		island_stitch_data[element1->island].num_rot_elements++;
+		island_stitch_data[element1->island].rotation += rotation;
+	} else {
+		island_stitch_data[element1->island].num_rot_elements_neg++;
+		island_stitch_data[element1->island].rotation_neg += rotation;
+	}
 }
 
 
@@ -515,7 +533,8 @@ static void stitch_island_calculate_vert_rotation(UvElement *element, StitchStat
 	float edgecos = 1.0f, edgesin = 0.0f;
 	int index;
 	UvElement *element_iter;
-	float rotation = 0;
+	float rotation = 0, rotation_neg = 0;
+	int rot_elem = 0, rot_elem_neg = 0;
 	BMLoop *l;
 
 	if (element->island == state->static_island && !state->midpoints)
@@ -544,16 +563,25 @@ static void stitch_island_calculate_vert_rotation(UvElement *element, StitchStat
 			negate_v2_v2(normal, state->normals + index_tmp2 * 2);
 			edgecos = dot_v2v2(normal, state->normals + index_tmp1 * 2);
 			edgesin = cross_v2v2(normal, state->normals + index_tmp1 * 2);
-			rotation += (edgesin > 0.0f) ?
-			    +acosf(max_ff(-1.0f, min_ff(1.0f, edgecos))) :
-			    -acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
+			if (edgesin > 0.0f) {
+			    rotation += acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
+				rot_elem++;
+			}
+			else {
+			    rotation_neg += acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
+				rot_elem_neg++;
+			}
 		}
 	}
 
-	if (state->midpoints)
+	if (state->midpoints) {
 		rotation /= 2.0f;
-	island_stitch_data[element->island].num_rot_elements++;
+		rotation_neg /= 2.0f;
+	}
+	island_stitch_data[element->island].num_rot_elements += rot_elem;
 	island_stitch_data[element->island].rotation += rotation;
+	island_stitch_data[element->island].num_rot_elements_neg += rot_elem_neg;
+	island_stitch_data[element->island].rotation_neg += rotation_neg;
 }