tornavis/source/blender/bmesh/operators/bmo_removedoubles.c

/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

/** \file \ingroup bmesh
 *
 * Welding and merging functionality.
 */

#include "MEM_guardedalloc.h"

#include "BLI_math.h"
#include "BLI_alloca.h"
#include "BLI_kdtree.h"
#include "BLI_listbase.h"
#include "BLI_utildefines_stack.h"
#include "BLI_stack.h"

#include "BKE_customdata.h"

#include "bmesh.h"
#include "intern/bmesh_operators_private.h"

static void remdoubles_splitface(BMFace *f, BMesh *bm, BMOperator *op, BMOpSlot *slot_targetmap)
{
	BMIter liter;
	BMLoop *l, *l_tar, *l_double;
	bool split = false;

	BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
		BMVert *v_tar = BMO_slot_map_elem_get(slot_targetmap, l->v);
		/* ok: if v_tar is NULL (e.g. not in the map) then it's
		 *     a target vert, otherwise it's a double */
		if (v_tar) {
			l_tar = BM_face_vert_share_loop(f, v_tar);

			if (l_tar && (l_tar != l) && !BM_loop_is_adjacent(l_tar, l)) {
				l_double = l;
				split = true;
				break;
			}
		}
	}

	if (split) {
		BMLoop *l_new;
		BMFace *f_new;

		f_new = BM_face_split(bm, f, l_double, l_tar, &l_new, NULL, false);

		remdoubles_splitface(f,     bm, op, slot_targetmap);
		remdoubles_splitface(f_new, bm, op, slot_targetmap);
	}
}

#define ELE_DEL		1
#define EDGE_COL	2
#define VERT_IN_FACE	4

/**
 * helper function for bmo_weld_verts_exec so we can use stack memory
 */
static BMFace *remdoubles_createface(BMesh *bm, BMFace *f, BMOpSlot *slot_targetmap, bool *r_created)
{
	BMEdge *e_new;

	BMEdge **edges = BLI_array_alloca(edges, f->len);  /* new ordered edges */
	BMVert **verts = BLI_array_alloca(verts, f->len);  /* new ordered verts */
	BMLoop **loops = BLI_array_alloca(loops, f->len);  /* original ordered loops to copy attrs into the new face */

	STACK_DECLARE(edges);
	STACK_DECLARE(loops);
	STACK_DECLARE(verts);

	STACK_INIT(edges, f->len);
	STACK_INIT(loops, f->len);
	STACK_INIT(verts, f->len);

	*r_created = false;

	{
#define LOOP_MAP_VERT_INIT(l_init, v_map, is_del) \
		v_map = l_init->v; \
		is_del = BMO_vert_flag_test_bool(bm, v_map, ELE_DEL); \
		if (is_del) { \
			v_map = BMO_slot_map_elem_get(slot_targetmap, v_map); \
		} ((void)0)


		BMLoop *l_first, *l_curr, *l_next;
		BMVert *v_curr;
		bool is_del_v_curr;

		l_curr = l_first = BM_FACE_FIRST_LOOP(f);
		LOOP_MAP_VERT_INIT(l_curr, v_curr, is_del_v_curr);

		do {
			BMVert *v_next;
			bool is_del_v_next;

			l_next = l_curr->next;
			LOOP_MAP_VERT_INIT(l_next, v_next, is_del_v_next);

			/* only search for a new edge if one of the verts is mapped */
			if ((is_del_v_curr || is_del_v_next) == 0) {
				e_new = l_curr->e;
			}
			else if (v_curr == v_next) {
				e_new = NULL;  /* skip */
			}
			else {
				e_new = BM_edge_exists(v_curr, v_next);
				BLI_assert(e_new);  /* never fails */
			}

			if (e_new) {
				if (UNLIKELY(BMO_vert_flag_test(bm, v_curr, VERT_IN_FACE))) {
					/* we can't make the face, bail out */
					STACK_CLEAR(edges);
					goto finally;
				}
				BMO_vert_flag_enable(bm, v_curr, VERT_IN_FACE);

				STACK_PUSH(edges, e_new);
				STACK_PUSH(loops, l_curr);
				STACK_PUSH(verts, v_curr);
			}

			v_curr = v_next;
			is_del_v_curr = is_del_v_next;
		} while ((l_curr = l_next) != l_first);

#undef LOOP_MAP_VERT_INIT

	}

finally:
	{
		uint i;
		for (i = 0; i < STACK_SIZE(verts); i++) {
			BMO_vert_flag_disable(bm, verts[i], VERT_IN_FACE);
		}
	}

	if (STACK_SIZE(edges) >= 3) {
		BMFace *f_new = BM_face_exists(verts, STACK_SIZE(verts));
		if (f_new) {
			return f_new;
		}
		f_new = BM_face_create(bm, verts, edges, STACK_SIZE(edges), f, BM_CREATE_NOP);
		BLI_assert(f_new != f);

		if (f_new) {
			uint i = 0;
			BMLoop *l_iter, *l_first;
			l_iter = l_first = BM_FACE_FIRST_LOOP(f_new);
			do {
				BM_elem_attrs_copy(bm, bm, loops[i], l_iter);
			} while ((void)i++, (l_iter = l_iter->next) != l_first);

			*r_created = true;
			return f_new;
		}
	}

	return NULL;
}


/**
 * \note with 'targetmap', multiple 'keys' are currently supported, though no callers should be using.
 * (because slot maps currently use GHash without the GHASH_FLAG_ALLOW_DUPES flag set)
 */
void bmo_weld_verts_exec(BMesh *bm, BMOperator *op)
{
	BMIter iter, liter;
	BMVert *v;
	BMEdge *e;
	BMLoop *l;
	BMFace *f;
	BMOpSlot *slot_targetmap = BMO_slot_get(op->slots_in, "targetmap");

	/* Maintain selection history. */
	const bool has_selected = !BLI_listbase_is_empty(&bm->selected);
	const bool use_targetmap_all = has_selected;
	GHash *targetmap_all = NULL;
	if (use_targetmap_all) {
		/* Map deleted to keep elem. */
		targetmap_all = BLI_ghash_ptr_new(__func__);
	}

	/* mark merge verts for deletion */
	BM_ITER_MESH (v, &iter, bm, BM_VERTS_OF_MESH) {
		BMVert *v_dst = BMO_slot_map_elem_get(slot_targetmap, v);
		if (v_dst != NULL) {
			BMO_vert_flag_enable(bm, v, ELE_DEL);

			/* merge the vertex flags, else we get randomly selected/unselected verts */
			BM_elem_flag_merge_ex(v, v_dst, BM_ELEM_HIDDEN);

			if (use_targetmap_all) {
				BLI_assert(v != v_dst);
				BLI_ghash_insert(targetmap_all, v, v_dst);
			}
		}
	}

	/* check if any faces are getting their own corners merged
	 * together, split face if so */
	BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
		remdoubles_splitface(f, bm, op, slot_targetmap);
	}

	BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
		BMVert *v1, *v2;
		const bool is_del_v1 = BMO_vert_flag_test_bool(bm, (v1 = e->v1), ELE_DEL);
		const bool is_del_v2 = BMO_vert_flag_test_bool(bm, (v2 = e->v2), ELE_DEL);

		if (is_del_v1 || is_del_v2) {
			if (is_del_v1)
				v1 = BMO_slot_map_elem_get(slot_targetmap, v1);
			if (is_del_v2)
				v2 = BMO_slot_map_elem_get(slot_targetmap, v2);

			if (v1 == v2) {
				BMO_edge_flag_enable(bm, e, EDGE_COL);
			}
			else {
				/* always merge flags, even for edges we already created */
				BMEdge *e_new = BM_edge_exists(v1, v2);
				if (e_new == NULL) {
					e_new = BM_edge_create(bm, v1, v2, e, BM_CREATE_NOP);
				}
				BM_elem_flag_merge_ex(e_new, e, BM_ELEM_HIDDEN);
				if (use_targetmap_all) {
					BLI_assert(e != e_new);
					BLI_ghash_insert(targetmap_all, e, e_new);
				}
			}

			BMO_edge_flag_enable(bm, e, ELE_DEL);
		}
	}

	/* faces get "modified" by creating new faces here, then at the
	 * end the old faces are deleted */
	BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
		bool vert_delete = false;
		int  edge_collapse = 0;

		BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
			if (BMO_vert_flag_test(bm, l->v, ELE_DEL)) {
				vert_delete = true;
			}
			if (BMO_edge_flag_test(bm, l->e, EDGE_COL)) {
				edge_collapse++;
			}
		}

		if (vert_delete) {
			bool use_in_place = false;
			BMFace *f_new = NULL;
			BMO_face_flag_enable(bm, f, ELE_DEL);

			if (f->len - edge_collapse >= 3) {
				bool created;
				f_new = remdoubles_createface(bm, f, slot_targetmap, &created);
				/* do this so we don't need to return a list of created faces */
				if (f_new) {
					if (created) {
						bmesh_face_swap_data(f_new, f);

						if (bm->use_toolflags) {
							SWAP(BMFlagLayer *, ((BMFace_OFlag *)f)->oflags, ((BMFace_OFlag *)f_new)->oflags);
						}

						BMO_face_flag_disable(bm, f, ELE_DEL);
						BM_face_kill(bm, f_new);
						use_in_place = true;
					}
					else {
						BM_elem_flag_merge_ex(f_new, f, BM_ELEM_HIDDEN);
					}
				}
			}

			if ((use_in_place == false) && (f_new != NULL)) {
				BLI_assert(f != f_new);
				if (use_targetmap_all) {
					BLI_ghash_insert(targetmap_all, f, f_new);
				}
				if (bm->act_face && (f == bm->act_face)) {
					bm->act_face = f_new;
				}
			}
		}
	}

	if (has_selected) {
		BM_select_history_merge_from_targetmap(bm, targetmap_all, targetmap_all, targetmap_all, true);
	}

	if (use_targetmap_all) {
		BLI_ghash_free(targetmap_all, NULL, NULL);
	}

	BMO_mesh_delete_oflag_context(bm, ELE_DEL, DEL_ONLYTAGGED);
}

#define VERT_KEEP	8
#define VERT_IN		32

#define EDGE_MARK	1

void bmo_pointmerge_facedata_exec(BMesh *bm, BMOperator *op)
{
	BMOIter siter;
	BMIter iter;
	BMVert *v, *vert_snap;
	BMLoop *l, *l_first = NULL;
	float fac;
	int i, tot;

	vert_snap = BMO_slot_buffer_get_single(BMO_slot_get(op->slots_in, "vert_snap"));
	tot = BM_vert_face_count(vert_snap);

	if (!tot)
		return;

	fac = 1.0f / tot;
	BM_ITER_ELEM (l, &iter, vert_snap, BM_LOOPS_OF_VERT) {
		if (l_first == NULL) {
			l_first = l;
		}

		for (i = 0; i < bm->ldata.totlayer; i++) {
			if (CustomData_layer_has_math(&bm->ldata, i)) {
				const int type = bm->ldata.layers[i].type;
				const int offset = bm->ldata.layers[i].offset;
				void *e1, *e2;

				e1 = BM_ELEM_CD_GET_VOID_P(l_first, offset);
				e2 = BM_ELEM_CD_GET_VOID_P(l,       offset);

				CustomData_data_multiply(type, e2, fac);

				if (l != l_first) {
					CustomData_data_add(type, e1, e2);
				}
			}
		}
	}

	BMO_ITER (v, &siter, op->slots_in, "verts", BM_VERT) {
		BM_ITER_ELEM (l, &iter, v, BM_LOOPS_OF_VERT) {
			if (l == l_first) {
				continue;
			}

			CustomData_bmesh_copy_data(&bm->ldata, &bm->ldata, l_first->head.data, &l->head.data);
		}
	}
}

void bmo_average_vert_facedata_exec(BMesh *bm, BMOperator *op)
{
	BMOIter siter;
	BMIter iter;
	BMVert *v;
	BMLoop *l /* , *firstl = NULL */;
	CDBlockBytes min, max;
	int i;

	for (i = 0; i < bm->ldata.totlayer; i++) {
		const int type = bm->ldata.layers[i].type;
		const int offset = bm->ldata.layers[i].offset;

		if (!CustomData_layer_has_math(&bm->ldata, i))
			continue;

		CustomData_data_initminmax(type, &min, &max);

		BMO_ITER (v, &siter, op->slots_in, "verts", BM_VERT) {
			BM_ITER_ELEM (l, &iter, v, BM_LOOPS_OF_VERT) {
				void *block = BM_ELEM_CD_GET_VOID_P(l, offset);
				CustomData_data_dominmax(type, block, &min, &max);
			}
		}

		CustomData_data_multiply(type, &min, 0.5f);
		CustomData_data_multiply(type, &max, 0.5f);
		CustomData_data_add(type, &min, &max);

		BMO_ITER (v, &siter, op->slots_in, "verts", BM_VERT) {
			BM_ITER_ELEM (l, &iter, v, BM_LOOPS_OF_VERT) {
				void *block = BM_ELEM_CD_GET_VOID_P(l, offset);
				CustomData_data_copy_value(type, &min, block);
			}
		}
	}
}

void bmo_pointmerge_exec(BMesh *bm, BMOperator *op)
{
	BMOperator weldop;
	BMOIter siter;
	BMVert *v, *vert_snap = NULL;
	float vec[3];
	BMOpSlot *slot_targetmap;

	BMO_slot_vec_get(op->slots_in, "merge_co", vec);

	//BMO_op_callf(bm, op->flag, "collapse_uvs edges=%s", op, "edges");
	BMO_op_init(bm, &weldop, op->flag, "weld_verts");

	slot_targetmap = BMO_slot_get(weldop.slots_in, "targetmap");

	BMO_ITER (v, &siter, op->slots_in, "verts", BM_VERT) {
		if (!vert_snap) {
			vert_snap = v;
			copy_v3_v3(vert_snap->co, vec);
		}
		else {
			BMO_slot_map_elem_insert(&weldop, slot_targetmap, v, vert_snap);
		}
	}

	BMO_op_exec(bm, &weldop);
	BMO_op_finish(bm, &weldop);
}

void bmo_collapse_exec(BMesh *bm, BMOperator *op)
{
	BMOperator weldop;
	BMWalker walker;
	BMIter iter;
	BMEdge *e;
	BLI_Stack *edge_stack;
	BMOpSlot *slot_targetmap;

	if (BMO_slot_bool_get(op->slots_in, "uvs")) {
		BMO_op_callf(bm, op->flag, "collapse_uvs edges=%s", op, "edges");
	}

	BMO_op_init(bm, &weldop, op->flag, "weld_verts");
	slot_targetmap = BMO_slot_get(weldop.slots_in, "targetmap");

	BMO_slot_buffer_flag_enable(bm, op->slots_in, "edges", BM_EDGE, EDGE_MARK);

	BMW_init(&walker, bm, BMW_VERT_SHELL,
	         BMW_MASK_NOP, EDGE_MARK, BMW_MASK_NOP,
	         BMW_FLAG_NOP, /* no need to use BMW_FLAG_TEST_HIDDEN, already marked data */
	         BMW_NIL_LAY);

	edge_stack = BLI_stack_new(sizeof(BMEdge *), __func__);

	BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
		float center[3];
		int count = 0;
		BMVert *v_tar;

		zero_v3(center);

		if (!BMO_edge_flag_test(bm, e, EDGE_MARK))
			continue;

		BLI_assert(BLI_stack_is_empty(edge_stack));

		for (e = BMW_begin(&walker, e->v1); e; e = BMW_step(&walker)) {
			BLI_stack_push(edge_stack, &e);

			add_v3_v3(center, e->v1->co);
			add_v3_v3(center, e->v2->co);

			count += 2;

			/* prevent adding to slot_targetmap multiple times */
			BM_elem_flag_disable(e->v1, BM_ELEM_TAG);
			BM_elem_flag_disable(e->v2, BM_ELEM_TAG);
		}

		if (!BLI_stack_is_empty(edge_stack)) {
			mul_v3_fl(center, 1.0f / count);

			/* snap edges to a point.  for initial testing purposes anyway */
			e = *(BMEdge **)BLI_stack_peek(edge_stack);
			v_tar = e->v1;

			while (!BLI_stack_is_empty(edge_stack)) {
				uint j;
				BLI_stack_pop(edge_stack, &e);

				for (j = 0; j < 2; j++) {
					BMVert *v_src = *((&e->v1) + j);

					copy_v3_v3(v_src->co, center);
					if ((v_src != v_tar) && !BM_elem_flag_test(v_src, BM_ELEM_TAG)) {
						BM_elem_flag_enable(v_src, BM_ELEM_TAG);
						BMO_slot_map_elem_insert(&weldop, slot_targetmap, v_src, v_tar);
					}
				}
			}
		}
	}

	BLI_stack_free(edge_stack);

	BMO_op_exec(bm, &weldop);
	BMO_op_finish(bm, &weldop);

	BMW_end(&walker);
}

/* uv collapse function */
static void bmo_collapsecon_do_layer(BMesh *bm, const int layer, const short oflag)
{
	const int type = bm->ldata.layers[layer].type;
	const int offset = bm->ldata.layers[layer].offset;
	BMIter iter, liter;
	BMFace *f;
	BMLoop *l, *l2;
	BMWalker walker;
	BLI_Stack *block_stack;
	CDBlockBytes min, max;

	BMW_init(&walker, bm, BMW_LOOPDATA_ISLAND,
	         BMW_MASK_NOP, oflag, BMW_MASK_NOP,
	         BMW_FLAG_NOP, /* no need to use BMW_FLAG_TEST_HIDDEN, already marked data */
	         layer);

	block_stack = BLI_stack_new(sizeof(void *), __func__);

	BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
		BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
			if (BMO_edge_flag_test(bm, l->e, oflag)) {
				/* walk */
				BLI_assert(BLI_stack_is_empty(block_stack));

				CustomData_data_initminmax(type, &min, &max);
				for (l2 = BMW_begin(&walker, l); l2; l2 = BMW_step(&walker)) {
					void *block = BM_ELEM_CD_GET_VOID_P(l2, offset);
					CustomData_data_dominmax(type, block, &min, &max);
					BLI_stack_push(block_stack, &block);
				}

				if (!BLI_stack_is_empty(block_stack)) {
					CustomData_data_multiply(type, &min, 0.5f);
					CustomData_data_multiply(type, &max, 0.5f);
					CustomData_data_add(type, &min, &max);

					/* snap CD (uv, vcol) points to their centroid */
					while (!BLI_stack_is_empty(block_stack)) {
						void *block;
						BLI_stack_pop(block_stack, &block);
						CustomData_data_copy_value(type, &min, block);
					}
				}
			}
		}
	}

	BLI_stack_free(block_stack);

	BMW_end(&walker);
}

void bmo_collapse_uvs_exec(BMesh *bm, BMOperator *op)
{
	const short oflag = EDGE_MARK;
	int i;

	/* check flags dont change once set */
#ifndef NDEBUG
	int tot_test;
#endif

	if (!CustomData_has_math(&bm->ldata)) {
		return;
	}

	BMO_slot_buffer_flag_enable(bm, op->slots_in, "edges", BM_EDGE, oflag);

#ifndef NDEBUG
	tot_test = BM_iter_mesh_count_flag(BM_EDGES_OF_MESH, bm, oflag, true);
#endif

	for (i = 0; i < bm->ldata.totlayer; i++) {
		if (CustomData_layer_has_math(&bm->ldata, i))
			bmo_collapsecon_do_layer(bm, i, oflag);
	}

#ifndef NDEBUG
	BLI_assert(tot_test == BM_iter_mesh_count_flag(BM_EDGES_OF_MESH, bm, EDGE_MARK, true));
#endif

}

static void bmesh_find_doubles_common(
        BMesh *bm, BMOperator *op,
        BMOperator *optarget, BMOpSlot *optarget_slot)
{
	const BMOpSlot *slot_verts = BMO_slot_get(op->slots_in, "verts");
	BMVert * const *verts = (BMVert **)slot_verts->data.buf;
	const int       verts_len = slot_verts->len;

	bool has_keep_vert = false;
	bool found_duplicates = false;

	const float dist  = BMO_slot_float_get(op->slots_in, "dist");

	/* Test whether keep_verts arg exists and is non-empty */
	if (BMO_slot_exists(op->slots_in, "keep_verts")) {
		BMOIter oiter;
		has_keep_vert = BMO_iter_new(&oiter, op->slots_in, "keep_verts", BM_VERT) != NULL;
	}

	/* Flag keep_verts */
	if (has_keep_vert) {
		BMO_slot_buffer_flag_enable(bm, op->slots_in, "keep_verts", BM_VERT, VERT_KEEP);
	}

	int *duplicates = MEM_mallocN(sizeof(int) * verts_len, __func__);
	{
		KDTree *tree = BLI_kdtree_new(verts_len);
		for (int i = 0; i < verts_len; i++) {
			BLI_kdtree_insert(tree, i, verts[i]->co);
			if (has_keep_vert && BMO_vert_flag_test(bm, verts[i], VERT_KEEP)) {
				duplicates[i] = i;
			}
			else {
				duplicates[i] = -1;
			}
		}

		BLI_kdtree_balance(tree);
		found_duplicates = BLI_kdtree_calc_duplicates_fast(tree, dist, false, duplicates) != 0;
		BLI_kdtree_free(tree);
	}

	if (found_duplicates) {
		for (int i = 0; i < verts_len; i++) {
			BMVert *v_check = verts[i];
			if (duplicates[i] == -1) {
				/* nop (others can use as target) */
			}
			else if (duplicates[i] == i) {
				/* keep (others can use as target) */
			}
			else {
				BMVert *v_other = verts[duplicates[i]];
				BLI_assert(ELEM(duplicates[duplicates[i]], -1, duplicates[i]));
				BMO_slot_map_elem_insert(optarget, optarget_slot, v_check, v_other);
			}
		}
	}

	MEM_freeN(duplicates);
}

void bmo_remove_doubles_exec(BMesh *bm, BMOperator *op)
{
	BMOperator weldop;
	BMOpSlot *slot_targetmap;

	BMO_op_init(bm, &weldop, op->flag, "weld_verts");
	slot_targetmap = BMO_slot_get(weldop.slots_in, "targetmap");
	bmesh_find_doubles_common(bm, op,
	                          &weldop, slot_targetmap);
	BMO_op_exec(bm, &weldop);
	BMO_op_finish(bm, &weldop);
}


void bmo_find_doubles_exec(BMesh *bm, BMOperator *op)
{
	BMOpSlot *slot_targetmap_out;
	slot_targetmap_out = BMO_slot_get(op->slots_out, "targetmap.out");
	bmesh_find_doubles_common(bm, op,
	                          op, slot_targetmap_out);
}

void bmo_automerge_exec(BMesh *bm, BMOperator *op)
{
	BMOperator findop, weldop;
	BMIter viter;
	BMVert *v;

	/* The "verts" input sent to this op is the set of verts that
	 * can be merged away into any other verts. Mark all other verts
	 * as VERT_KEEP. */
	BMO_slot_buffer_flag_enable(bm, op->slots_in, "verts", BM_VERT, VERT_IN);
	BM_ITER_MESH (v, &viter, bm, BM_VERTS_OF_MESH) {
		if (!BMO_vert_flag_test(bm, v, VERT_IN)) {
			BMO_vert_flag_enable(bm, v, VERT_KEEP);
		}
	}

	/* Search for doubles among all vertices, but only merge non-VERT_KEEP
	 * vertices into VERT_KEEP vertices. */
	BMO_op_initf(bm, &findop, op->flag, "find_doubles verts=%av keep_verts=%fv", VERT_KEEP);
	BMO_slot_copy(op,      slots_in, "dist",
	              &findop, slots_in, "dist");
	BMO_op_exec(bm, &findop);

	/* weld the vertices */
	BMO_op_init(bm, &weldop, op->flag, "weld_verts");
	BMO_slot_copy(&findop, slots_out, "targetmap.out",
	              &weldop, slots_in,  "targetmap");
	BMO_op_exec(bm, &weldop);

	BMO_op_finish(bm, &findop);
	BMO_op_finish(bm, &weldop);
}