Fix part of T44320 selecting islands can fail.

Issue here is simple and has been fixed in other places such as
texpainting: Basically if face has different winding, do not calculate
it as adjucent to the other face, even if UV is identical.

This allows us to stack islands of symmetrical closed meshes on top of
one another and still be able to select the two identical island halfs
(provided the normals are correct of course).

2 files changed, 61 insertions, 25 deletions

diff --git a/source/blender/blenkernel/intern/mesh_mapping.c b/source/blender/blenkernel/intern/mesh_mapping.c
index 8d9fbe46f19..974e8118b15 100644
--- a/source/blender/blenkernel/intern/mesh_mapping.c
+++ b/source/blender/blenkernel/intern/mesh_mapping.c
@@ -30,7 +30,9 @@
 #include "MEM_guardedalloc.h"
 
 #include "DNA_meshdata_types.h"
+#include "DNA_vec_types.h"
 
+#include "BLI_buffer.h"
 #include "BLI_utildefines.h"
 #include "BLI_bitmap.h"
 #include "BLI_math.h"
@@ -62,6 +64,8 @@ UvVertMap *BKE_mesh_uv_vert_map_create(struct MPoly *mpoly, struct MLoop *mloop,
 	int i, totuv, nverts;
 
 	totuv = 0;
+	bool *winding;
+	BLI_buffer_declare_static(vec2f, tf_uv_buf, BLI_BUFFER_NOP, 32);
 
 	/* generate UvMapVert array */
 	mp = mpoly;
@@ -72,7 +76,9 @@ UvVertMap *BKE_mesh_uv_vert_map_create(struct MPoly *mpoly, struct MLoop *mloop,
 	if (totuv == 0)
 		return NULL;
 
+	winding = MEM_callocN(sizeof(*winding) * totpoly, "winding");
 	vmap = (UvVertMap *)MEM_callocN(sizeof(*vmap), "UvVertMap");
+
 	if (!vmap)
 		return NULL;
 
@@ -87,6 +93,8 @@ UvVertMap *BKE_mesh_uv_vert_map_create(struct MPoly *mpoly, struct MLoop *mloop,
 	mp = mpoly;
 	for (a = 0; a < totpoly; a++, mp++) {
 		if (!selected || (!(mp->flag & ME_HIDE) && (mp->flag & ME_FACE_SEL))) {
+			float (*tf_uv)[2]     = (float (*)[2])BLI_buffer_resize_data(&tf_uv_buf, vec2f, mp->totloop);
+
 			nverts = mp->totloop;
 
 			for (i = 0; i < nverts; i++) {
@@ -95,8 +103,12 @@ UvVertMap *BKE_mesh_uv_vert_map_create(struct MPoly *mpoly, struct MLoop *mloop,
 				buf->separate = 0;
 				buf->next = vmap->vert[mloop[mp->loopstart + i].v];
 				vmap->vert[mloop[mp->loopstart + i].v] = buf;
+
+				copy_v2_v2(tf_uv[i], mloopuv[mpoly[a].loopstart + i].uv);
 				buf++;
 			}
+
+			winding[a] = cross_poly_v2((const float (*)[2])tf_uv, (unsigned int)nverts) > 0;
 		}
 	}
 
@@ -123,7 +135,9 @@ UvVertMap *BKE_mesh_uv_vert_map_create(struct MPoly *mpoly, struct MLoop *mloop,
 				sub_v2_v2v2(uvdiff, uv2, uv);
 
 
-				if (fabsf(uv[0] - uv2[0]) < limit[0] && fabsf(uv[1] - uv2[1]) < limit[1]) {
+				if (fabsf(uv[0] - uv2[0]) < limit[0] && fabsf(uv[1] - uv2[1]) < limit[1] &&
+				    winding[iterv->f] == winding[v->f])
+				{
 					if (lastv) lastv->next = next;
 					else vlist = next;
 					iterv->next = newvlist;
@@ -141,6 +155,9 @@ UvVertMap *BKE_mesh_uv_vert_map_create(struct MPoly *mpoly, struct MLoop *mloop,
 		vmap->vert[a] = newvlist;
 	}
 
+	MEM_freeN(winding);
+	BLI_buffer_free(&tf_uv_buf);
+
 	return vmap;
 }
 
diff --git a/source/blender/editors/mesh/editmesh_utils.c b/source/blender/editors/mesh/editmesh_utils.c
index 86cd75eed7a..1875689415a 100644
--- a/source/blender/editors/mesh/editmesh_utils.c
+++ b/source/blender/editors/mesh/editmesh_utils.c
@@ -37,6 +37,7 @@
 
 #include "BLI_math.h"
 #include "BLI_alloca.h"
+#include "BLI_buffer.h"
 #include "BLI_listbase.h"
 
 #include "BKE_DerivedMesh.h"
@@ -625,11 +626,14 @@ UvVertMap *BM_uv_vert_map_create(BMesh *bm, bool use_select, const float limit[2
 	/* MTexPoly *tf; */ /* UNUSED */
 	MLoopUV *luv;
 	unsigned int a;
-	int totverts, i, totuv;
+	int totverts, i, totuv, totfaces;
 	const int cd_loop_uv_offset = CustomData_get_offset(&bm->ldata, CD_MLOOPUV);
+	bool *winding;
+	BLI_buffer_declare_static(vec2f, tf_uv_buf, BLI_BUFFER_NOP, BM_DEFAULT_NGON_STACK_SIZE);
 
 	BM_mesh_elem_index_ensure(bm, BM_VERT | BM_FACE);
 	
+	totfaces = bm->totface;
 	totverts = bm->totvert;
 	totuv = 0;
 
@@ -650,17 +654,18 @@ UvVertMap *BM_uv_vert_map_create(BMesh *bm, bool use_select, const float limit[2
 
 	vmap->vert = (UvMapVert **)MEM_callocN(sizeof(*vmap->vert) * totverts, "UvMapVert_pt");
 	buf = vmap->buf = (UvMapVert *)MEM_callocN(sizeof(*vmap->buf) * totuv, "UvMapVert");
+	winding = MEM_callocN(sizeof(*winding) * totfaces, "winding");
 
 	if (!vmap->vert || !vmap->buf) {
 		BKE_mesh_uv_vert_map_free(vmap);
 		return NULL;
 	}
 	
-	a = 0;
-	BM_ITER_MESH (efa, &iter, bm, BM_FACES_OF_MESH) {
+	BM_ITER_MESH_INDEX (efa, &iter, bm, BM_FACES_OF_MESH, a) {
 		if ((use_select == false) || BM_elem_flag_test(efa, BM_ELEM_SELECT)) {
-			i = 0;
-			BM_ITER_ELEM (l, &liter, efa, BM_LOOPS_OF_FACE) {
+			float (*tf_uv)[2]     = (float (*)[2])BLI_buffer_resize_data(&tf_uv_buf, vec2f, efa->len);
+
+			BM_ITER_ELEM_INDEX(l, &liter, efa, BM_LOOPS_OF_FACE, i) {
 				buf->tfindex = i;
 				buf->f = a;
 				buf->separate = 0;
@@ -668,17 +673,18 @@ UvVertMap *BM_uv_vert_map_create(BMesh *bm, bool use_select, const float limit[2
 				buf->next = vmap->vert[BM_elem_index_get(l->v)];
 				vmap->vert[BM_elem_index_get(l->v)] = buf;
 				
+				luv = BM_ELEM_CD_GET_VOID_P(l, cd_loop_uv_offset);
+				copy_v2_v2(tf_uv[i], luv->uv);
+
 				buf++;
-				i++;
 			}
-		}
 
-		a++;
+			winding[a] = cross_poly_v2((const float (*)[2])tf_uv, efa->len) > 0;
+		}
 	}
 	
 	/* sort individual uvs for each vert */
-	a = 0;
-	BM_ITER_MESH (ev, &iter, bm, BM_VERTS_OF_MESH) {
+	BM_ITER_MESH_INDEX (ev, &iter, bm, BM_VERTS_OF_MESH, a) {
 		UvMapVert *newvlist = NULL, *vlist = vmap->vert[a];
 		UvMapVert *iterv, *v, *lastv, *next;
 		float *uv, *uv2, uvdiff[2];
@@ -710,7 +716,9 @@ UvVertMap *BM_uv_vert_map_create(BMesh *bm, bool use_select, const float limit[2
 				
 				sub_v2_v2v2(uvdiff, uv2, uv);
 
-				if (fabsf(uvdiff[0]) < limit[0] && fabsf(uvdiff[1]) < limit[1]) {
+				if (fabsf(uvdiff[0]) < limit[0] && fabsf(uvdiff[1]) < limit[1] &&
+				    winding[iterv->f] == winding[v->f])
+				{
 					if (lastv) lastv->next = next;
 					else vlist = next;
 					iterv->next = newvlist;
@@ -727,9 +735,11 @@ UvVertMap *BM_uv_vert_map_create(BMesh *bm, bool use_select, const float limit[2
 		}
 
 		vmap->vert[a] = newvlist;
-		a++;
 	}
 
+	MEM_freeN(winding);
+	BLI_buffer_free(&tf_uv_buf);
+
 	return vmap;
 }
 
@@ -755,9 +765,11 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm, const bool selected, const boo
 	UvElement *islandbuf;
 	/* island number for faces */
 	int *island_number;
+	bool *winding;
+	BLI_buffer_declare_static(vec2f, tf_uv_buf, BLI_BUFFER_NOP, BM_DEFAULT_NGON_STACK_SIZE);
 
 	MLoopUV *luv;
-	int totverts, i, totuv, j, nislands = 0, islandbufsize = 0;
+	int totverts, totfaces, i, totuv, j, nislands = 0, islandbufsize = 0;
 
 	unsigned int *map;
 	BMFace **stack;
@@ -767,13 +779,12 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm, const bool selected, const boo
 
 	BM_mesh_elem_index_ensure(bm, BM_VERT | BM_FACE);
 
+	totfaces = bm->totface;
 	totverts = bm->totvert;
 	totuv = 0;
 
-	island_number = MEM_mallocN(sizeof(*stack) * bm->totface, "uv_island_number_face");
-	if (!island_number) {
-		return NULL;
-	}
+	island_number = MEM_mallocN(sizeof(*stack) * totfaces, "uv_island_number_face");
+	winding = MEM_callocN(sizeof(*winding) * totfaces, "winding");
 
 	/* generate UvElement array */
 	BM_ITER_MESH (efa, &iter, bm, BM_FACES_OF_MESH) {
@@ -801,10 +812,11 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm, const bool selected, const boo
 		return NULL;
 	}
 
-	j = 0;
-	BM_ITER_MESH (efa, &iter, bm, BM_FACES_OF_MESH) {
-		island_number[j++] = INVALID_ISLAND;
+	BM_ITER_MESH_INDEX (efa, &iter, bm, BM_FACES_OF_MESH, j) {
+		island_number[j] = INVALID_ISLAND;
 		if (!selected || BM_elem_flag_test(efa, BM_ELEM_SELECT)) {
+			float (*tf_uv)[2]     = (float (*)[2])BLI_buffer_resize_data(&tf_uv_buf, vec2f, efa->len);
+
 			BM_ITER_ELEM_INDEX (l, &liter, efa, BM_LOOPS_OF_FACE, i) {
 				buf->l = l;
 				buf->separate = 0;
@@ -814,14 +826,18 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm, const bool selected, const boo
 				buf->next = element_map->vert[BM_elem_index_get(l->v)];
 				element_map->vert[BM_elem_index_get(l->v)] = buf;
 
+				luv = BM_ELEM_CD_GET_VOID_P(l, cd_loop_uv_offset);
+				copy_v2_v2(tf_uv[i], luv->uv);
+
 				buf++;
 			}
+
+			winding[j] = cross_poly_v2((const float (*)[2])tf_uv, efa->len) > 0;
 		}
 	}
 
 	/* sort individual uvs for each vert */
-	i = 0;
-	BM_ITER_MESH (ev, &iter, bm, BM_VERTS_OF_MESH) {
+	BM_ITER_MESH_INDEX (ev, &iter, bm, BM_VERTS_OF_MESH, i) {
 		UvElement *newvlist = NULL, *vlist = element_map->vert[i];
 		UvElement *iterv, *v, *lastv, *next;
 		float *uv, *uv2, uvdiff[2];
@@ -848,7 +864,8 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm, const bool selected, const boo
 
 				sub_v2_v2v2(uvdiff, uv2, uv);
 
-				if (fabsf(uvdiff[0]) < STD_UV_CONNECT_LIMIT && fabsf(uvdiff[1]) < STD_UV_CONNECT_LIMIT) {
+				if (fabsf(uvdiff[0]) < STD_UV_CONNECT_LIMIT && fabsf(uvdiff[1]) < STD_UV_CONNECT_LIMIT &&
+				    winding[BM_elem_index_get(iterv->l->f)] == winding[BM_elem_index_get(v->l->f)]) {
 					if (lastv) lastv->next = next;
 					else vlist = next;
 					iterv->next = newvlist;
@@ -865,7 +882,6 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm, const bool selected, const boo
 		}
 
 		element_map->vert[i] = newvlist;
-		i++;
 	}
 
 	if (do_islands) {
@@ -958,7 +974,10 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm, const bool selected, const boo
 		MEM_freeN(stack);
 		MEM_freeN(map);
 	}
+
 	MEM_freeN(island_number);
+	MEM_freeN(winding);
+	BLI_buffer_free(&tf_uv_buf);
 
 	return element_map;
 }