Cleanup: rename bmesh_queries -> bmesh_query

Other files with the same purpose already used 'query'.

1 files changed, 2751 insertions, 0 deletions

diff --git a/source/blender/bmesh/intern/bmesh_query.c b/source/blender/bmesh/intern/bmesh_query.c
new file mode 100644
index 00000000000..33ad7836893
--- /dev/null
+++ b/source/blender/bmesh/intern/bmesh_query.c
@@ -0,0 +1,2751 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * 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.
+ *
+ * Contributor(s): Joseph Eagar, Geoffrey Bantle, Campbell Barton
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/bmesh/intern/bmesh_query.c
+ *  \ingroup bmesh
+ *
+ * This file contains functions for answering common
+ * Topological and geometric queries about a mesh, such
+ * as, "What is the angle between these two faces?" or,
+ * "How many faces are incident upon this vertex?" Tool
+ * authors should use the functions in this file instead
+ * of inspecting the mesh structure directly.
+ */
+
+#include "MEM_guardedalloc.h"
+
+#include "BLI_math.h"
+#include "BLI_alloca.h"
+#include "BLI_linklist.h"
+#include "BLI_utildefines_stack.h"
+
+#include "BKE_customdata.h"
+
+#include "bmesh.h"
+#include "intern/bmesh_private.h"
+
+/**
+ * \brief Other Loop in Face Sharing an Edge
+ *
+ * Finds the other loop that shares \a v with \a e loop in \a f.
+ * <pre>
+ *     +----------+
+ *     |          |
+ *     |    f     |
+ *     |          |
+ *     +----------+ <-- return the face loop of this vertex.
+ *     v --> e
+ *     ^     ^ <------- These vert args define direction
+ *                      in the face to check.
+ *                      The faces loop direction is ignored.
+ * </pre>
+ *
+ * \note caller must ensure \a e is used in \a f
+ */
+BMLoop *BM_face_other_edge_loop(BMFace *f, BMEdge *e, BMVert *v)
+{
+	BMLoop *l = BM_face_edge_share_loop(f, e);
+	BLI_assert(l != NULL);
+	return BM_loop_other_edge_loop(l, v);
+}
+
+/**
+ * See #BM_face_other_edge_loop This is the same functionality
+ * to be used when the edges loop is already known.
+ */
+BMLoop *BM_loop_other_edge_loop(BMLoop *l, BMVert *v)
+{
+	BLI_assert(BM_vert_in_edge(l->e, v));
+	return l->v == v ? l->prev : l->next;
+}
+
+/**
+ * \brief Other Loop in Face Sharing a Vertex
+ *
+ * Finds the other loop in a face.
+ *
+ * This function returns a loop in \a f that shares an edge with \a v
+ * The direction is defined by \a v_prev, where the return value is
+ * the loop of what would be 'v_next'
+ * <pre>
+ *     +----------+ <-- return the face loop of this vertex.
+ *     |          |
+ *     |    f     |
+ *     |          |
+ *     +----------+
+ *     v_prev --> v
+ *     ^^^^^^     ^ <-- These vert args define direction
+ *                      in the face to check.
+ *                      The faces loop direction is ignored.
+ * </pre>
+ *
+ * \note \a v_prev and \a v _implicitly_ define an edge.
+ */
+BMLoop *BM_face_other_vert_loop(BMFace *f, BMVert *v_prev, BMVert *v)
+{
+	BMLoop *l_iter = BM_face_vert_share_loop(f, v);
+
+	BLI_assert(BM_edge_exists(v_prev, v) != NULL);
+
+	if (l_iter) {
+		if (l_iter->prev->v == v_prev) {
+			return l_iter->next;
+		}
+		else if (l_iter->next->v == v_prev) {
+			return l_iter->prev;
+		}
+		else {
+			/* invalid args */
+			BLI_assert(0);
+			return NULL;
+		}
+	}
+	else {
+		/* invalid args */
+		BLI_assert(0);
+		return NULL;
+	}
+}
+
+/**
+ * \brief Other Loop in Face Sharing a Vert
+ *
+ * Finds the other loop that shares \a v with \a e loop in \a f.
+ * <pre>
+ *     +----------+ <-- return the face loop of this vertex.
+ *     |          |
+ *     |          |
+ *     |          |
+ *     +----------+ <-- This vertex defines the direction.
+ *           l    v
+ *           ^ <------- This loop defines both the face to search
+ *                      and the edge, in combination with 'v'
+ *                      The faces loop direction is ignored.
+ * </pre>
+ */
+BMLoop *BM_loop_other_vert_loop(BMLoop *l, BMVert *v)
+{
+#if 0 /* works but slow */
+	return BM_face_other_vert_loop(l->f, BM_edge_other_vert(l->e, v), v);
+#else
+	BMEdge *e = l->e;
+	BMVert *v_prev = BM_edge_other_vert(e, v);
+	if (l->v == v) {
+		if (l->prev->v == v_prev) {
+			return l->next;
+		}
+		else {
+			BLI_assert(l->next->v == v_prev);
+
+			return l->prev;
+		}
+	}
+	else {
+		BLI_assert(l->v == v_prev);
+
+		if (l->prev->v == v) {
+			return l->prev->prev;
+		}
+		else {
+			BLI_assert(l->next->v == v);
+			return l->next->next;
+		}
+	}
+#endif
+}
+
+/**
+ * Check if verts share a face.
+ */
+bool BM_vert_pair_share_face_check(
+        BMVert *v_a, BMVert *v_b)
+{
+	if (v_a->e && v_b->e) {
+		BMIter iter;
+		BMFace *f;
+
+		BM_ITER_ELEM (f, &iter, v_a, BM_FACES_OF_VERT) {
+			if (BM_vert_in_face(v_b, f)) {
+				return true;
+			}
+		}
+	}
+
+	return false;
+}
+
+bool BM_vert_pair_share_face_check_cb(
+        BMVert *v_a, BMVert *v_b,
+        bool (*test_fn)(BMFace *, void *user_data), void *user_data)
+{
+	if (v_a->e && v_b->e) {
+		BMIter iter;
+		BMFace *f;
+
+		BM_ITER_ELEM (f, &iter, v_a, BM_FACES_OF_VERT) {
+			if (test_fn(f, user_data)) {
+				if (BM_vert_in_face(v_b, f)) {
+					return true;
+				}
+			}
+		}
+	}
+
+	return false;
+}
+
+/**
+ * Given 2 verts, find the smallest face they share and give back both loops.
+ */
+BMFace *BM_vert_pair_share_face_by_len(
+        BMVert *v_a, BMVert *v_b,
+        BMLoop **r_l_a, BMLoop **r_l_b,
+        const bool allow_adjacent)
+{
+	BMLoop *l_cur_a = NULL, *l_cur_b = NULL;
+	BMFace *f_cur = NULL;
+
+	if (v_a->e && v_b->e) {
+		BMIter iter;
+		BMLoop *l_a, *l_b;
+
+		BM_ITER_ELEM (l_a, &iter, v_a, BM_LOOPS_OF_VERT) {
+			if ((f_cur == NULL) || (l_a->f->len < f_cur->len)) {
+				l_b = BM_face_vert_share_loop(l_a->f, v_b);
+				if (l_b && (allow_adjacent || !BM_loop_is_adjacent(l_a, l_b))) {
+					f_cur = l_a->f;
+					l_cur_a = l_a;
+					l_cur_b = l_b;
+				}
+			}
+		}
+	}
+
+	*r_l_a = l_cur_a;
+	*r_l_b = l_cur_b;
+
+	return f_cur;
+}
+
+BMFace *BM_edge_pair_share_face_by_len(
+        BMEdge *e_a, BMEdge *e_b,
+        BMLoop **r_l_a, BMLoop **r_l_b,
+        const bool allow_adjacent)
+{
+	BMLoop *l_cur_a = NULL, *l_cur_b = NULL;
+	BMFace *f_cur = NULL;
+
+	if (e_a->l && e_b->l) {
+		BMIter iter;
+		BMLoop *l_a, *l_b;
+
+		BM_ITER_ELEM (l_a, &iter, e_a, BM_LOOPS_OF_EDGE) {
+			if ((f_cur == NULL) || (l_a->f->len < f_cur->len)) {
+				l_b = BM_face_edge_share_loop(l_a->f, e_b);
+				if (l_b && (allow_adjacent || !BM_loop_is_adjacent(l_a, l_b))) {
+					f_cur = l_a->f;
+					l_cur_a = l_a;
+					l_cur_b = l_b;
+				}
+			}
+		}
+	}
+
+	*r_l_a = l_cur_a;
+	*r_l_b = l_cur_b;
+
+	return f_cur;
+}
+
+static float bm_face_calc_split_dot(BMLoop *l_a, BMLoop *l_b)
+{
+	float no[2][3];
+
+	if ((BM_face_calc_normal_subset(l_a, l_b, no[0]) != 0.0f) &&
+	    (BM_face_calc_normal_subset(l_b, l_a, no[1]) != 0.0f))
+	{
+		return dot_v3v3(no[0], no[1]);
+	}
+	else {
+		return -1.0f;
+	}
+}
+
+/**
+ * Check if a point is inside the corner defined by a loop
+ * (within the 2 planes defined by the loops corner & face normal).
+ *
+ * \return signed, squared distance to the loops planes, less than 0.0 when outside.
+ */
+float BM_loop_point_side_of_loop_test(const BMLoop *l, const float co[3])
+{
+	const float *axis = l->f->no;
+	return dist_signed_squared_to_corner_v3v3v3(co, l->prev->v->co, l->v->co, l->next->v->co, axis);
+}
+
+/**
+ * Check if a point is inside the edge defined by a loop
+ * (within the plane defined by the loops edge & face normal).
+ *
+ * \return signed, squared distance to the edge plane, less than 0.0 when outside.
+ */
+float BM_loop_point_side_of_edge_test(const BMLoop *l, const float co[3])
+{
+	const float *axis = l->f->no;
+	float dir[3];
+	float plane[4];
+
+	sub_v3_v3v3(dir, l->next->v->co, l->v->co);
+	cross_v3_v3v3(plane, axis, dir);
+
+	plane[3] = -dot_v3v3(plane, l->v->co);
+	return dist_signed_squared_to_plane_v3(co, plane);
+}
+
+/**
+ * Given 2 verts, find a face they share that has the lowest angle across these verts and give back both loops.
+ *
+ * This can be better then #BM_vert_pair_share_face_by_len because concave splits are ranked lowest.
+ */
+BMFace *BM_vert_pair_share_face_by_angle(
+        BMVert *v_a, BMVert *v_b,
+        BMLoop **r_l_a, BMLoop **r_l_b,
+        const bool allow_adjacent)
+{
+	BMLoop *l_cur_a = NULL, *l_cur_b = NULL;
+	BMFace *f_cur = NULL;
+
+	if (v_a->e && v_b->e) {
+		BMIter iter;
+		BMLoop *l_a, *l_b;
+		float dot_best = -1.0f;
+
+		BM_ITER_ELEM (l_a, &iter, v_a, BM_LOOPS_OF_VERT) {
+			l_b = BM_face_vert_share_loop(l_a->f, v_b);
+			if (l_b && (allow_adjacent || !BM_loop_is_adjacent(l_a, l_b))) {
+
+				if (f_cur == NULL) {
+					f_cur = l_a->f;
+					l_cur_a = l_a;
+					l_cur_b = l_b;
+				}
+				else {
+					/* avoid expensive calculations if we only ever find one face */
+					float dot;
+					if (dot_best == -1.0f) {
+						dot_best = bm_face_calc_split_dot(l_cur_a, l_cur_b);
+					}
+
+					dot = bm_face_calc_split_dot(l_a, l_b);
+					if (dot > dot_best) {
+						dot_best = dot;
+
+						f_cur = l_a->f;
+						l_cur_a = l_a;
+						l_cur_b = l_b;
+					}
+				}
+			}
+		}
+	}
+
+	*r_l_a = l_cur_a;
+	*r_l_b = l_cur_b;
+
+	return f_cur;
+}
+
+
+/**
+ * Get the first loop of a vert. Uses the same initialization code for the first loop of the
+ * iterator API
+ */
+BMLoop *BM_vert_find_first_loop(BMVert *v)
+{
+	return v->e ? bmesh_disk_faceloop_find_first(v->e, v) : NULL;
+}
+
+/**
+ * Returns true if the vertex is used in a given face.
+ */
+bool BM_vert_in_face(BMVert *v, BMFace *f)
+{
+	BMLoop *l_iter, *l_first;
+
+#ifdef USE_BMESH_HOLES
+	BMLoopList *lst;
+	for (lst = f->loops.first; lst; lst = lst->next)
+#endif
+	{
+#ifdef USE_BMESH_HOLES
+		l_iter = l_first = lst->first;
+#else
+		l_iter = l_first = f->l_first;
+#endif
+		do {
+			if (l_iter->v == v) {
+				return true;
+			}
+		} while ((l_iter = l_iter->next) != l_first);
+	}
+
+	return false;
+}
+
+/**
+ * Compares the number of vertices in an array
+ * that appear in a given face
+ */
+int BM_verts_in_face_count(BMVert **varr, int len, BMFace *f)
+{
+	BMLoop *l_iter, *l_first;
+
+#ifdef USE_BMESH_HOLES
+	BMLoopList *lst;
+#endif
+
+	int i, count = 0;
+
+	for (i = 0; i < len; i++) {
+		BM_ELEM_API_FLAG_ENABLE(varr[i], _FLAG_OVERLAP);
+	}
+
+#ifdef USE_BMESH_HOLES
+	for (lst = f->loops.first; lst; lst = lst->next)
+#endif
+	{
+
+#ifdef USE_BMESH_HOLES
+		l_iter = l_first = lst->first;
+#else
+		l_iter = l_first = f->l_first;
+#endif
+
+		do {
+			if (BM_ELEM_API_FLAG_TEST(l_iter->v, _FLAG_OVERLAP)) {
+				count++;
+			}
+
+		} while ((l_iter = l_iter->next) != l_first);
+	}
+
+	for (i = 0; i < len; i++) {
+		BM_ELEM_API_FLAG_DISABLE(varr[i], _FLAG_OVERLAP);
+	}
+
+	return count;
+}
+
+
+/**
+ * Return true if all verts are in the face.
+ */
+bool BM_verts_in_face(BMVert **varr, int len, BMFace *f)
+{
+	BMLoop *l_iter, *l_first;
+
+#ifdef USE_BMESH_HOLES
+	BMLoopList *lst;
+#endif
+
+	int i;
+	bool ok = true;
+
+	/* simple check, we know can't succeed */
+	if (f->len < len) {
+		return false;
+	}
+
+	for (i = 0; i < len; i++) {
+		BM_ELEM_API_FLAG_ENABLE(varr[i], _FLAG_OVERLAP);
+	}
+
+#ifdef USE_BMESH_HOLES
+	for (lst = f->loops.first; lst; lst = lst->next)
+#endif
+	{
+
+#ifdef USE_BMESH_HOLES
+		l_iter = l_first = lst->first;
+#else
+		l_iter = l_first = f->l_first;
+#endif
+
+		do {
+			if (BM_ELEM_API_FLAG_TEST(l_iter->v, _FLAG_OVERLAP)) {
+				/* pass */
+			}
+			else {
+				ok = false;
+				break;
+			}
+
+		} while ((l_iter = l_iter->next) != l_first);
+	}
+
+	for (i = 0; i < len; i++) {
+		BM_ELEM_API_FLAG_DISABLE(varr[i], _FLAG_OVERLAP);
+	}
+
+	return ok;
+}
+
+/**
+ * Returns whether or not a given edge is part of a given face.
+ */
+bool BM_edge_in_face(const BMEdge *e, const BMFace *f)
+{
+	if (e->l) {
+		const BMLoop *l_iter, *l_first;
+
+		l_iter = l_first = e->l;
+		do {
+			if (l_iter->f == f) {
+				return true;
+			}
+		} while ((l_iter = l_iter->radial_next) != l_first);
+	}
+
+	return false;
+}
+
+/**
+ * Given a edge and a loop (assumes the edge is manifold). returns
+ * the other faces loop, sharing the same vertex.
+ *
+ * <pre>
+ * +-------------------+
+ * |                   |
+ * |                   |
+ * |l_other <-- return |
+ * +-------------------+ <-- A manifold edge between 2 faces
+ * |l    e  <-- edge   |
+ * |^ <-------- loop   |
+ * |                   |
+ * +-------------------+
+ * </pre>
+ */
+BMLoop *BM_edge_other_loop(BMEdge *e, BMLoop *l)
+{
+	BMLoop *l_other;
+
+	// BLI_assert(BM_edge_is_manifold(e));  // TOO strict, just check if we have another radial face
+	BLI_assert(e->l && e->l->radial_next != e->l);
+	BLI_assert(BM_vert_in_edge(e, l->v));
+
+	l_other = (l->e == e) ? l : l->prev;
+	l_other = l_other->radial_next;
+	BLI_assert(l_other->e == e);
+
+	if (l_other->v == l->v) {
+		/* pass */
+	}
+	else if (l_other->next->v == l->v) {
+		l_other = l_other->next;
+	}
+	else {
+		BLI_assert(0);
+	}
+
+	return l_other;
+}
+
+/**
+ * Utility function to step around a fan of loops,
+ * using an edge to mark the previous side.
+ *
+ * \note all edges must be manifold,
+ * once a non manifold edge is hit, return NULL.
+ *
+ * <pre>
+ *                ,.,-->|
+ *            _,-'      |
+ *          ,'          | (notice how 'e_step'
+ *         /            |  and 'l' define the
+ *        /             |  direction the arrow
+ *       |     return   |  points).
+ *       |     loop --> |
+ * ---------------------+---------------------
+ *         ^      l --> |
+ *         |            |
+ *  assign e_step       |
+ *                      |
+ *   begin e_step ----> |
+ *                      |
+ * </pre>
+ */
+
+BMLoop *BM_vert_step_fan_loop(BMLoop *l, BMEdge **e_step)
+{
+	BMEdge *e_prev = *e_step;
+	BMEdge *e_next;
+	if (l->e == e_prev) {
+		e_next = l->prev->e;
+	}
+	else if (l->prev->e == e_prev) {
+		e_next = l->e;
+	}
+	else {
+		BLI_assert(0);
+		return NULL;
+	}
+
+	if (BM_edge_is_manifold(e_next)) {
+		return BM_edge_other_loop((*e_step = e_next), l);
+	}
+	else {
+		return NULL;
+	}
+}
+
+
+
+/**
+ * The function takes a vertex at the center of a fan and returns the opposite edge in the fan.
+ * All edges in the fan must be manifold, otherwise return NULL.
+ *
+ * \note This could (probably) be done more efficiently.
+ */
+BMEdge *BM_vert_other_disk_edge(BMVert *v, BMEdge *e_first)
+{
+	BMLoop *l_a;
+	int tot = 0;
+	int i;
+
+	BLI_assert(BM_vert_in_edge(e_first, v));
+
+	l_a = e_first->l;
+	do {
+		l_a = BM_loop_other_vert_loop(l_a, v);
+		l_a = BM_vert_in_edge(l_a->e, v) ? l_a : l_a->prev;
+		if (BM_edge_is_manifold(l_a->e)) {
+			l_a = l_a->radial_next;
+		}
+		else {
+			return NULL;
+		}
+
+		tot++;
+	} while (l_a != e_first->l);
+
+	/* we know the total, now loop half way */
+	tot /= 2;
+	i = 0;
+
+	l_a = e_first->l;
+	do {
+		if (i == tot) {
+			l_a = BM_vert_in_edge(l_a->e, v) ? l_a : l_a->prev;
+			return l_a->e;
+		}
+
+		l_a = BM_loop_other_vert_loop(l_a, v);
+		l_a = BM_vert_in_edge(l_a->e, v) ? l_a : l_a->prev;
+		if (BM_edge_is_manifold(l_a->e)) {
+			l_a = l_a->radial_next;
+		}
+		/* this wont have changed from the previous loop */
+
+
+		i++;
+	} while (l_a != e_first->l);
+
+	return NULL;
+}
+
+/**
+ * Returns edge length
+ */
+float BM_edge_calc_length(const BMEdge *e)
+{
+	return len_v3v3(e->v1->co, e->v2->co);
+}
+
+/**
+ * Returns edge length squared (for comparisons)
+ */
+float BM_edge_calc_length_squared(const BMEdge *e)
+{
+	return len_squared_v3v3(e->v1->co, e->v2->co);
+}
+
+/**
+ * Utility function, since enough times we have an edge
+ * and want to access 2 connected faces.
+ *
+ * \return true when only 2 faces are found.
+ */
+bool BM_edge_face_pair(BMEdge *e, BMFace **r_fa, BMFace **r_fb)
+{
+	BMLoop *la, *lb;
+
+	if ((la = e->l) &&
+	    (lb = la->radial_next) &&
+	    (la != lb) &&
+	    (lb->radial_next == la))
+	{
+		*r_fa = la->f;
+		*r_fb = lb->f;
+		return true;
+	}
+	else {
+		*r_fa = NULL;
+		*r_fb = NULL;
+		return false;
+	}
+}
+
+/**
+ * Utility function, since enough times we have an edge
+ * and want to access 2 connected loops.
+ *
+ * \return true when only 2 faces are found.
+ */
+bool BM_edge_loop_pair(BMEdge *e, BMLoop **r_la, BMLoop **r_lb)
+{
+	BMLoop *la, *lb;
+
+	if ((la = e->l) &&
+	    (lb = la->radial_next) &&
+	    (la != lb) &&
+	    (lb->radial_next == la))
+	{
+		*r_la = la;
+		*r_lb = lb;
+		return true;
+	}
+	else {
+		*r_la = NULL;
+		*r_lb = NULL;
+		return false;
+	}
+}
+
+/**
+ * Fast alternative to ``(BM_vert_edge_count(v) == 2)``
+ */
+bool BM_vert_is_edge_pair(const BMVert *v)
+{
+	const BMEdge *e = v->e;
+	if (e) {
+		BMEdge *e_other = BM_DISK_EDGE_NEXT(e, v);
+		return ((e_other != e) && (BM_DISK_EDGE_NEXT(e_other, v) == e));
+	}
+	return false;
+}
+
+/**
+ * Fast alternative to ``(BM_vert_edge_count(v) == 2)``
+ * that checks both edges connect to the same faces.
+ */
+bool BM_vert_is_edge_pair_manifold(const BMVert *v)
+{
+	const BMEdge *e = v->e;
+	if (e) {
+		BMEdge *e_other = BM_DISK_EDGE_NEXT(e, v);
+		if (((e_other != e) && (BM_DISK_EDGE_NEXT(e_other, v) == e))) {
+			return BM_edge_is_manifold(e) && BM_edge_is_manifold(e_other);
+		}
+	}
+	return false;
+}
+
+/**
+ * Access a verts 2 connected edges.
+ *
+ * \return true when only 2 verts are found.
+ */
+bool BM_vert_edge_pair(BMVert *v, BMEdge **r_e_a, BMEdge **r_e_b)
+{
+	BMEdge *e_a = v->e;
+	if (e_a) {
+		BMEdge *e_b = BM_DISK_EDGE_NEXT(e_a, v);
+		if ((e_b != e_a) && (BM_DISK_EDGE_NEXT(e_b, v) == e_a)) {
+			*r_e_a = e_a;
+			*r_e_b = e_b;
+			return true;
+		}
+	}
+
+	*r_e_a = NULL;
+	*r_e_b = NULL;
+	return false;
+}
+
+/**
+ *	Returns the number of edges around this vertex.
+ */
+int BM_vert_edge_count(const BMVert *v)
+{
+	return bmesh_disk_count(v);
+}
+
+int BM_vert_edge_count_at_most(const BMVert *v, const int count_max)
+{
+	return bmesh_disk_count_at_most(v, count_max);
+}
+
+int BM_vert_edge_count_nonwire(const BMVert *v)
+{
+	int count = 0;
+	BMIter eiter;
+	BMEdge *edge;
+	BM_ITER_ELEM (edge, &eiter, (BMVert *)v, BM_EDGES_OF_VERT) {
+		if (edge->l) {
+			count++;
+		}
+	}
+	return count;
+}
+/**
+ *	Returns the number of faces around this edge
+ */
+int BM_edge_face_count(const BMEdge *e)
+{
+	int count = 0;
+
+	if (e->l) {
+		BMLoop *l_iter, *l_first;
+
+		l_iter = l_first = e->l;
+		do {
+			count++;
+		} while ((l_iter = l_iter->radial_next) != l_first);
+	}
+
+	return count;
+}
+
+int BM_edge_face_count_at_most(const BMEdge *e, const int count_max)
+{
+	int count = 0;
+
+	if (e->l) {
+		BMLoop *l_iter, *l_first;
+
+		l_iter = l_first = e->l;
+		do {
+			count++;
+			if (count == count_max) {
+				break;
+			}
+		} while ((l_iter = l_iter->radial_next) != l_first);
+	}
+
+	return count;
+}
+
+/**
+ * Returns the number of faces around this vert
+ * length matches #BM_LOOPS_OF_VERT iterator
+ */
+int BM_vert_face_count(const BMVert *v)
+{
+	return bmesh_disk_facevert_count(v);
+}
+
+int BM_vert_face_count_at_most(const BMVert *v, int count_max)
+{
+	return bmesh_disk_facevert_count_at_most(v, count_max);
+}
+
+/**
+ * Return true if the vertex is connected to _any_ faces.
+ *
+ * same as ``BM_vert_face_count(v) != 0`` or ``BM_vert_find_first_loop(v) == NULL``
+ */
+bool BM_vert_face_check(const BMVert *v)
+{
+	if (v->e != NULL) {
+		const BMEdge *e_iter, *e_first;
+		e_first = e_iter = v->e;
+		do {
+			if (e_iter->l != NULL) {
+				return true;
+			}
+		} while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e_first);
+	}
+	return false;
+}
+
+/**
+ * Tests whether or not the vertex is part of a wire edge.
+ * (ie: has no faces attached to it)
+ */
+bool BM_vert_is_wire(const BMVert *v)
+{
+	if (v->e) {
+		BMEdge *e_first, *e_iter;
+
+		e_first = e_iter = v->e;
+		do {
+			if (e_iter->l) {
+				return false;
+			}
+		} while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e_first);
+
+		return true;
+	}
+	else {
+		return false;
+	}
+}
+
+/**
+ * A vertex is non-manifold if it meets the following conditions:
+ * 1: Loose - (has no edges/faces incident upon it).
+ * 2: Joins two distinct regions - (two pyramids joined at the tip).
+ * 3: Is part of an edge with more than 2 faces.
+ * 4: Is part of a wire edge.
+ */
+bool BM_vert_is_manifold(const BMVert *v)
+{
+	BMEdge *e_iter, *e_first, *e_prev;
+	BMLoop *l_iter, *l_first;
+	int loop_num = 0, loop_num_region = 0, boundary_num = 0;
+
+	if (v->e == NULL) {
+		/* loose vert */
+		return false;
+	}
+
+	/* count edges while looking for non-manifold edges */
+	e_first = e_iter = v->e;
+	/* may be null */
+	l_first = e_iter->l;
+	do {
+		/* loose edge or edge shared by more than two faces,
+		 * edges with 1 face user are OK, otherwise we could
+		 * use BM_edge_is_manifold() here */
+		if (e_iter->l == NULL || (e_iter->l != e_iter->l->radial_next->radial_next)) {
+			return false;
+		}
+
+		/* count radial loops */
+		if (e_iter->l->v == v) {
+			loop_num += 1;
+		}
+
+		if (!BM_edge_is_boundary(e_iter)) {
+			/* non boundary check opposite loop */
+			if (e_iter->l->radial_next->v == v) {
+				loop_num += 1;
+			}
+		}
+		else {
+			/* start at the boundary */
+			l_first = e_iter->l;
+			boundary_num += 1;
+			/* >2 boundaries cant be manifold */
+			if (boundary_num == 3) {
+				return false;
+			}
+		}
+	} while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e_first);
+
+	e_first = l_first->e;
+	l_first = (l_first->v == v) ? l_first : l_first->next;
+	BLI_assert(l_first->v == v);
+
+	l_iter = l_first;
+	e_prev = e_first;
+
+	do {
+		loop_num_region += 1;
+	} while (((l_iter = BM_vert_step_fan_loop(l_iter, &e_prev)) != l_first) && (l_iter != NULL));
+
+	return (loop_num == loop_num_region);
+}
+
+#define LOOP_VISIT _FLAG_WALK
+#define EDGE_VISIT _FLAG_WALK
+
+static int bm_loop_region_count__recursive(BMEdge *e, BMVert *v)
+{
+	BMLoop *l_iter, *l_first;
+	int count = 0;
+
+	BLI_assert(!BM_ELEM_API_FLAG_TEST(e, EDGE_VISIT));
+	BM_ELEM_API_FLAG_ENABLE(e, EDGE_VISIT);
+
+	l_iter = l_first = e->l;
+	do {
+		if (l_iter->v == v) {
+			BMEdge *e_other = l_iter->prev->e;
+			if (!BM_ELEM_API_FLAG_TEST(l_iter, LOOP_VISIT)) {
+				BM_ELEM_API_FLAG_ENABLE(l_iter, LOOP_VISIT);
+				count += 1;
+			}
+			if (!BM_ELEM_API_FLAG_TEST(e_other, EDGE_VISIT)) {
+				count += bm_loop_region_count__recursive(e_other, v);
+			}
+		}
+		else if (l_iter->next->v == v) {
+			BMEdge *e_other = l_iter->next->e;
+			if (!BM_ELEM_API_FLAG_TEST(l_iter->next, LOOP_VISIT)) {
+				BM_ELEM_API_FLAG_ENABLE(l_iter->next, LOOP_VISIT);
+				count += 1;
+			}
+			if (!BM_ELEM_API_FLAG_TEST(e_other, EDGE_VISIT)) {
+				count += bm_loop_region_count__recursive(e_other, v);
+			}
+		}
+		else {
+			BLI_assert(0);
+		}
+	} while ((l_iter = l_iter->radial_next) != l_first);
+
+	return count;
+}
+
+static int bm_loop_region_count__clear(BMLoop *l)
+{
+	int count = 0;
+	BMEdge *e_iter, *e_first;
+
+	/* clear flags */
+	e_iter = e_first = l->e;
+	do {
+		BM_ELEM_API_FLAG_DISABLE(e_iter, EDGE_VISIT);
+		if (e_iter->l) {
+			BMLoop *l_iter, *l_first;
+			l_iter = l_first = e_iter->l;
+			do {
+				if (l_iter->v == l->v) {
+					BM_ELEM_API_FLAG_DISABLE(l_iter, LOOP_VISIT);
+					count += 1;
+				}
+			} while ((l_iter = l_iter->radial_next) != l_first);
+		}
+	} while ((e_iter = BM_DISK_EDGE_NEXT(e_iter, l->v)) != e_first);
+
+	return count;
+}
+
+/**
+ * The number of loops connected to this loop (not including disconnected regions).
+ */
+int BM_loop_region_loops_count_at_most(BMLoop *l, int *r_loop_total)
+{
+	const int count       = bm_loop_region_count__recursive(l->e, l->v);
+	const int count_total = bm_loop_region_count__clear(l);
+	if (r_loop_total) {
+		*r_loop_total = count_total;
+	}
+	return count;
+}
+
+#undef LOOP_VISIT
+#undef EDGE_VISIT
+
+int BM_loop_region_loops_count(BMLoop *l)
+{
+	return BM_loop_region_loops_count_at_most(l, NULL);
+}
+
+/**
+ * A version of #BM_vert_is_manifold
+ * which only checks if we're connected to multiple isolated regions.
+ */
+bool BM_vert_is_manifold_region(const BMVert *v)
+{
+	BMLoop *l_first = BM_vert_find_first_loop((BMVert *)v);
+	if (l_first) {
+		int count, count_total;
+		count = BM_loop_region_loops_count_at_most(l_first, &count_total);
+		return (count == count_total);
+	}
+	return true;
+}
+
+/**
+ * Check if the edge is convex or concave
+ * (depends on face winding)
+ */
+bool BM_edge_is_convex(const BMEdge *e)
+{
+	if (BM_edge_is_manifold(e)) {
+		BMLoop *l1 = e->l;
+		BMLoop *l2 = e->l->radial_next;
+		if (!equals_v3v3(l1->f->no, l2->f->no)) {
+			float cross[3];
+			float l_dir[3];
+			cross_v3_v3v3(cross, l1->f->no, l2->f->no);
+			/* we assume contiguous normals, otherwise the result isn't meaningful */
+			sub_v3_v3v3(l_dir, l1->next->v->co, l1->v->co);
+			return (dot_v3v3(l_dir, cross) > 0.0f);
+		}
+	}
+	return true;
+}
+
+/**
+ * \return true when loop customdata is contiguous.
+ */
+bool BM_edge_is_contiguous_loop_cd(
+        const BMEdge *e,
+        const int cd_loop_type, const int cd_loop_offset)
+{
+	BLI_assert(cd_loop_offset != -1);
+
+	if (e->l && e->l->radial_next != e->l) {
+		const BMLoop *l_base_v1 = e->l;
+		const BMLoop *l_base_v2 = e->l->next;
+		const void *l_base_cd_v1 = BM_ELEM_CD_GET_VOID_P(l_base_v1, cd_loop_offset);
+		const void *l_base_cd_v2 = BM_ELEM_CD_GET_VOID_P(l_base_v2, cd_loop_offset);
+		const BMLoop *l_iter = e->l->radial_next;
+		do {
+			const BMLoop *l_iter_v1;
+			const BMLoop *l_iter_v2;
+			const void *l_iter_cd_v1;
+			const void *l_iter_cd_v2;
+
+			if (l_iter->v == l_base_v1->v) {
+				l_iter_v1 = l_iter;
+				l_iter_v2 = l_iter->next;
+			}
+			else {
+				l_iter_v1 = l_iter->next;
+				l_iter_v2 = l_iter;
+			}
+			BLI_assert((l_iter_v1->v == l_base_v1->v) &&
+			           (l_iter_v2->v == l_base_v2->v));
+
+			l_iter_cd_v1 = BM_ELEM_CD_GET_VOID_P(l_iter_v1, cd_loop_offset);
+			l_iter_cd_v2 = BM_ELEM_CD_GET_VOID_P(l_iter_v2, cd_loop_offset);
+
+
+			if ((CustomData_data_equals(cd_loop_type, l_base_cd_v1, l_iter_cd_v1) == 0) ||
+			    (CustomData_data_equals(cd_loop_type, l_base_cd_v2, l_iter_cd_v2) == 0))
+			{
+				return false;
+			}
+
+		} while ((l_iter = l_iter->radial_next) != e->l);
+	}
+	return true;
+}
+
+bool BM_vert_is_boundary(const BMVert *v)
+{
+	if (v->e) {
+		BMEdge *e_first, *e_iter;
+
+		e_first = e_iter = v->e;
+		do {
+			if (BM_edge_is_boundary(e_iter)) {
+				return true;
+			}
+		} while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e_first);
+
+		return false;
+	}
+	else {
+		return false;
+	}
+}
+
+/**
+ * Returns the number of faces that are adjacent to both f1 and f2,
+ * \note Could be sped up a bit by not using iterators and by tagging
+ * faces on either side, then count the tags rather then searching.
+ */
+int BM_face_share_face_count(BMFace *f1, BMFace *f2)
+{
+	BMIter iter1, iter2;
+	BMEdge *e;
+	BMFace *f;
+	int count = 0;
+
+	BM_ITER_ELEM (e, &iter1, f1, BM_EDGES_OF_FACE) {
+		BM_ITER_ELEM (f, &iter2, e, BM_FACES_OF_EDGE) {
+			if (f != f1 && f != f2 && BM_face_share_edge_check(f, f2))
+				count++;
+		}
+	}
+
+	return count;
+}
+
+/**
+ * same as #BM_face_share_face_count but returns a bool
+ */
+bool BM_face_share_face_check(BMFace *f1, BMFace *f2)
+{
+	BMIter iter1, iter2;
+	BMEdge *e;
+	BMFace *f;
+
+	BM_ITER_ELEM (e, &iter1, f1, BM_EDGES_OF_FACE) {
+		BM_ITER_ELEM (f, &iter2, e, BM_FACES_OF_EDGE) {
+			if (f != f1 && f != f2 && BM_face_share_edge_check(f, f2))
+				return true;
+		}
+	}
+
+	return false;
+}
+
+/**
+ *  Counts the number of edges two faces share (if any)
+ */
+int BM_face_share_edge_count(BMFace *f_a, BMFace *f_b)
+{
+	BMLoop *l_iter;
+	BMLoop *l_first;
+	int count = 0;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f_a);
+	do {
+		if (BM_edge_in_face(l_iter->e, f_b)) {
+			count++;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+
+	return count;
+}
+
+/**
+ *  Returns true if the faces share an edge
+ */
+bool BM_face_share_edge_check(BMFace *f1, BMFace *f2)
+{
+	BMLoop *l_iter;
+	BMLoop *l_first;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f1);
+	do {
+		if (BM_edge_in_face(l_iter->e, f2)) {
+			return true;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+
+	return false;
+}
+
+/**
+ *  Counts the number of verts two faces share (if any).
+ */
+int BM_face_share_vert_count(BMFace *f_a, BMFace *f_b)
+{
+	BMLoop *l_iter;
+	BMLoop *l_first;
+	int count = 0;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f_a);
+	do {
+		if (BM_vert_in_face(l_iter->v, f_b)) {
+			count++;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+
+	return count;
+}
+
+/**
+ *  Returns true if the faces share a vert.
+ */
+bool BM_face_share_vert_check(BMFace *f_a, BMFace *f_b)
+{
+	BMLoop *l_iter;
+	BMLoop *l_first;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f_a);
+	do {
+		if (BM_vert_in_face(l_iter->v, f_b)) {
+			return true;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+
+	return false;
+}
+
+/**
+ * Returns true when 2 loops share an edge (are adjacent in the face-fan)
+ */
+bool BM_loop_share_edge_check(BMLoop *l_a, BMLoop *l_b)
+{
+	BLI_assert(l_a->v == l_b->v);
+	return (ELEM(l_a->e, l_b->e, l_b->prev->e) ||
+	        ELEM(l_b->e, l_a->e, l_a->prev->e));
+}
+
+/**
+ * Test if e1 shares any faces with e2
+ */
+bool BM_edge_share_face_check(BMEdge *e1, BMEdge *e2)
+{
+	BMLoop *l;
+	BMFace *f;
+
+	if (e1->l && e2->l) {
+		l = e1->l;
+		do {
+			f = l->f;
+			if (BM_edge_in_face(e2, f)) {
+				return true;
+			}
+			l = l->radial_next;
+		} while (l != e1->l);
+	}
+	return false;
+}
+
+/**
+ *	Test if e1 shares any quad faces with e2
+ */
+bool BM_edge_share_quad_check(BMEdge *e1, BMEdge *e2)
+{
+	BMLoop *l;
+	BMFace *f;
+
+	if (e1->l && e2->l) {
+		l = e1->l;
+		do {
+			f = l->f;
+			if (f->len == 4) {
+				if (BM_edge_in_face(e2, f)) {
+					return true;
+				}
+			}
+			l = l->radial_next;
+		} while (l != e1->l);
+	}
+	return false;
+}
+
+/**
+ *	Tests to see if e1 shares a vertex with e2
+ */
+bool BM_edge_share_vert_check(BMEdge *e1, BMEdge *e2)
+{
+	return (e1->v1 == e2->v1 ||
+	        e1->v1 == e2->v2 ||
+	        e1->v2 == e2->v1 ||
+	        e1->v2 == e2->v2);
+}
+
+/**
+ *	Return the shared vertex between the two edges or NULL
+ */
+BMVert *BM_edge_share_vert(BMEdge *e1, BMEdge *e2)
+{
+	BLI_assert(e1 != e2);
+	if (BM_vert_in_edge(e2, e1->v1)) {
+		return e1->v1;
+	}
+	else if (BM_vert_in_edge(e2, e1->v2)) {
+		return e1->v2;
+	}
+	else {
+		return NULL;
+	}
+}
+
+/**
+ * \brief Return the Loop Shared by Edge and Vert
+ *
+ * Finds the loop used which uses \a  in face loop \a l
+ *
+ * \note this function takes a loop rather then an edge
+ * so we can select the face that the loop should be from.
+ */
+BMLoop *BM_edge_vert_share_loop(BMLoop *l, BMVert *v)
+{
+	BLI_assert(BM_vert_in_edge(l->e, v));
+	if (l->v == v) {
+		return l;
+	}
+	else {
+		return l->next;
+	}
+}
+
+/**
+ * \brief Return the Loop Shared by Face and Vertex
+ *
+ * Finds the loop used which uses \a v in face loop \a l
+ *
+ * \note currently this just uses simple loop in future may be sped up
+ * using radial vars
+ */
+BMLoop *BM_face_vert_share_loop(BMFace *f, BMVert *v)
+{
+	BMLoop *l_first;
+	BMLoop *l_iter;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+	do {
+		if (l_iter->v == v) {
+			return l_iter;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+
+	return NULL;
+}
+
+/**
+ * \brief Return the Loop Shared by Face and Edge
+ *
+ * Finds the loop used which uses \a e in face loop \a l
+ *
+ * \note currently this just uses simple loop in future may be sped up
+ * using radial vars
+ */
+BMLoop *BM_face_edge_share_loop(BMFace *f, BMEdge *e)
+{
+	BMLoop *l_first;
+	BMLoop *l_iter;
+
+	l_iter = l_first = e->l;
+	do {
+		if (l_iter->f == f) {
+			return l_iter;
+		}
+	} while ((l_iter = l_iter->radial_next) != l_first);
+
+	return NULL;
+}
+
+/**
+ * Returns the verts of an edge as used in a face
+ * if used in a face at all, otherwise just assign as used in the edge.
+ *
+ * Useful to get a deterministic winding order when calling
+ * BM_face_create_ngon() on an arbitrary array of verts,
+ * though be sure to pick an edge which has a face.
+ *
+ * \note This is in fact quite a simple check, mainly include this function so the intent is more obvious.
+ * We know these 2 verts will _always_ make up the loops edge
+ */
+void BM_edge_ordered_verts_ex(
+        const BMEdge *edge, BMVert **r_v1, BMVert **r_v2,
+        const BMLoop *edge_loop)
+{
+	BLI_assert(edge_loop->e == edge);
+	(void)edge; /* quiet warning in release build */
+	*r_v1 = edge_loop->v;
+	*r_v2 = edge_loop->next->v;
+}
+
+void BM_edge_ordered_verts(const BMEdge *edge, BMVert **r_v1, BMVert **r_v2)
+{
+	BM_edge_ordered_verts_ex(edge, r_v1, r_v2, edge->l);
+}
+
+/**
+ * \return The previous loop, over \a eps_sq distance from \a l (or \a NULL if l_stop is reached).
+ */
+BMLoop *BM_loop_find_prev_nodouble(BMLoop *l, BMLoop *l_stop, const float eps_sq)
+{
+	BMLoop *l_step = l->prev;
+
+	BLI_assert(!ELEM(l_stop, NULL, l));
+
+	while (UNLIKELY(len_squared_v3v3(l->v->co, l_step->v->co) < eps_sq)) {
+		l_step = l_step->prev;
+		BLI_assert(l_step != l);
+		if (UNLIKELY(l_step == l_stop)) {
+			return NULL;
+		}
+	}
+
+	return l_step;
+}
+
+/**
+ * \return The next loop, over \a eps_sq distance from \a l (or \a NULL if l_stop is reached).
+ */
+BMLoop *BM_loop_find_next_nodouble(BMLoop *l, BMLoop *l_stop, const float eps_sq)
+{
+	BMLoop *l_step = l->next;
+
+	BLI_assert(!ELEM(l_stop, NULL, l));
+
+	while (UNLIKELY(len_squared_v3v3(l->v->co, l_step->v->co) < eps_sq)) {
+		l_step = l_step->next;
+		BLI_assert(l_step != l);
+		if (UNLIKELY(l_step == l_stop)) {
+			return NULL;
+		}
+	}
+
+	return l_step;
+}
+
+/**
+ * Check if the loop is convex or concave
+ * (depends on face normal)
+ */
+bool BM_loop_is_convex(const BMLoop *l)
+{
+	float e_dir_prev[3];
+	float e_dir_next[3];
+	float l_no[3];
+
+	sub_v3_v3v3(e_dir_prev, l->prev->v->co, l->v->co);
+	sub_v3_v3v3(e_dir_next, l->next->v->co, l->v->co);
+	cross_v3_v3v3(l_no, e_dir_next, e_dir_prev);
+	return dot_v3v3(l_no, l->f->no) > 0.0f;
+}
+
+/**
+ * Calculates the angle between the previous and next loops
+ * (angle at this loops face corner).
+ *
+ * \return angle in radians
+ */
+float BM_loop_calc_face_angle(const BMLoop *l)
+{
+	return angle_v3v3v3(l->prev->v->co,
+	                    l->v->co,
+	                    l->next->v->co);
+}
+
+/**
+ * \brief BM_loop_calc_face_normal
+ *
+ * Calculate the normal at this loop corner or fallback to the face normal on straight lines.
+ *
+ * \param l: The loop to calculate the normal at.
+ * \param epsilon_sq: Value to avoid numeric errors (1e-5f works well).
+ * \param r_normal: Resulting normal.
+ */
+float BM_loop_calc_face_normal_safe_ex(const BMLoop *l, const float epsilon_sq, float r_normal[3])
+{
+	/* Note: we cannot use result of normal_tri_v3 here to detect colinear vectors (vertex on a straight line)
+	 * from zero value, because it does not normalize both vectors before making crossproduct.
+	 * Instead of adding two costly normalize computations, just check ourselves for colinear case. */
+	/* Note: FEPSILON might need some finer tweaking at some point? Seems to be working OK for now though. */
+	float v1[3], v2[3], v_tmp[3];
+	sub_v3_v3v3(v1, l->prev->v->co, l->v->co);
+	sub_v3_v3v3(v2, l->next->v->co, l->v->co);
+
+	const float fac =
+	        ((v2[0] == 0.0f) ?
+	        ((v2[1] == 0.0f) ?
+	        ((v2[2] == 0.0f) ?  0.0f : v1[2] / v2[2]) : v1[1] / v2[1]) : v1[0] / v2[0]);
+
+	mul_v3_v3fl(v_tmp, v2, fac);
+	sub_v3_v3(v_tmp, v1);
+	if (fac != 0.0f && !is_zero_v3(v1) && len_squared_v3(v_tmp) > epsilon_sq) {
+		/* Not co-linear, we can compute crossproduct and normalize it into normal. */
+		cross_v3_v3v3(r_normal, v1, v2);
+		return normalize_v3(r_normal);
+	}
+	else {
+		copy_v3_v3(r_normal, l->f->no);
+		return 0.0f;
+	}
+}
+
+/**
+ * #BM_loop_calc_face_normal_safe_ex with pre-defined sane epsilon.
+ *
+ * Since this doesn't scale baed on triangle size, fixed value works well.
+ */
+float BM_loop_calc_face_normal_safe(const BMLoop *l, float r_normal[3])
+{
+	return BM_loop_calc_face_normal_safe_ex(l, 1e-5f, r_normal);
+}
+
+/**
+ * \brief BM_loop_calc_face_normal
+ *
+ * Calculate the normal at this loop corner or fallback to the face normal on straight lines.
+ *
+ * \param l The loop to calculate the normal at
+ * \param r_normal Resulting normal
+ * \return The length of the cross product (double the area).
+ */
+float BM_loop_calc_face_normal(const BMLoop *l, float r_normal[3])
+{
+	float v1[3], v2[3];
+	sub_v3_v3v3(v1, l->prev->v->co, l->v->co);
+	sub_v3_v3v3(v2, l->next->v->co, l->v->co);
+
+	cross_v3_v3v3(r_normal, v1, v2);
+	const float len = normalize_v3(r_normal);
+	if (UNLIKELY(len == 0.0f)) {
+		copy_v3_v3(r_normal, l->f->no);
+	}
+	return len;
+}
+
+/**
+ * \brief BM_loop_calc_face_direction
+ *
+ * Calculate the direction a loop is pointing.
+ *
+ * \param l The loop to calculate the direction at
+ * \param r_dir Resulting direction
+ */
+void BM_loop_calc_face_direction(const BMLoop *l, float r_dir[3])
+{
+	float v_prev[3];
+	float v_next[3];
+
+	sub_v3_v3v3(v_prev, l->v->co, l->prev->v->co);
+	sub_v3_v3v3(v_next, l->next->v->co, l->v->co);
+
+	normalize_v3(v_prev);
+	normalize_v3(v_next);
+
+	add_v3_v3v3(r_dir, v_prev, v_next);
+	normalize_v3(r_dir);
+}
+
+/**
+ * \brief BM_loop_calc_face_tangent
+ *
+ * Calculate the tangent at this loop corner or fallback to the face normal on straight lines.
+ * This vector always points inward into the face.
+ *
+ * \param l The loop to calculate the tangent at
+ * \param r_tangent Resulting tangent
+ */
+void BM_loop_calc_face_tangent(const BMLoop *l, float r_tangent[3])
+{
+	float v_prev[3];
+	float v_next[3];
+	float dir[3];
+
+	sub_v3_v3v3(v_prev, l->prev->v->co, l->v->co);
+	sub_v3_v3v3(v_next, l->v->co, l->next->v->co);
+
+	normalize_v3(v_prev);
+	normalize_v3(v_next);
+	add_v3_v3v3(dir, v_prev, v_next);
+
+	if (compare_v3v3(v_prev, v_next, FLT_EPSILON * 10.0f) == false) {
+		float nor[3]; /* for this purpose doesn't need to be normalized */
+		cross_v3_v3v3(nor, v_prev, v_next);
+		/* concave face check */
+		if (UNLIKELY(dot_v3v3(nor, l->f->no) < 0.0f)) {
+			negate_v3(nor);
+		}
+		cross_v3_v3v3(r_tangent, dir, nor);
+	}
+	else {
+		/* prev/next are the same - compare with face normal since we don't have one */
+		cross_v3_v3v3(r_tangent, dir, l->f->no);
+	}
+
+	normalize_v3(r_tangent);
+}
+
+/**
+ * \brief BMESH EDGE/FACE ANGLE
+ *
+ *  Calculates the angle between two faces.
+ *  Assumes the face normals are correct.
+ *
+ * \return angle in radians
+ */
+float BM_edge_calc_face_angle_ex(const BMEdge *e, const float fallback)
+{
+	if (BM_edge_is_manifold(e)) {
+		const BMLoop *l1 = e->l;
+		const BMLoop *l2 = e->l->radial_next;
+		return angle_normalized_v3v3(l1->f->no, l2->f->no);
+	}
+	else {
+		return fallback;
+	}
+}
+float BM_edge_calc_face_angle(const BMEdge *e)
+{
+	return BM_edge_calc_face_angle_ex(e, DEG2RADF(90.0f));
+}
+
+/**
+ * \brief BMESH EDGE/FACE ANGLE
+ *
+ *  Calculates the angle between two faces.
+ *  Assumes the face normals are correct.
+ *
+ * \return angle in radians
+ */
+float BM_edge_calc_face_angle_signed_ex(const BMEdge *e, const float fallback)
+{
+	if (BM_edge_is_manifold(e)) {
+		BMLoop *l1 = e->l;
+		BMLoop *l2 = e->l->radial_next;
+		const float angle = angle_normalized_v3v3(l1->f->no, l2->f->no);
+		return BM_edge_is_convex(e) ? angle : -angle;
+	}
+	else {
+		return fallback;
+	}
+}
+float BM_edge_calc_face_angle_signed(const BMEdge *e)
+{
+	return BM_edge_calc_face_angle_signed_ex(e, DEG2RADF(90.0f));
+}
+
+/**
+ * \brief BMESH EDGE/FACE TANGENT
+ *
+ * Calculate the tangent at this loop corner or fallback to the face normal on straight lines.
+ * This vector always points inward into the face.
+ *
+ * \brief BM_edge_calc_face_tangent
+ * \param e
+ * \param e_loop The loop to calculate the tangent at,
+ * used to get the face and winding direction.
+ * \param r_tangent The loop corner tangent to set
+ */
+
+void BM_edge_calc_face_tangent(const BMEdge *e, const BMLoop *e_loop, float r_tangent[3])
+{
+	float tvec[3];
+	BMVert *v1, *v2;
+	BM_edge_ordered_verts_ex(e, &v1, &v2, e_loop);
+
+	sub_v3_v3v3(tvec, v1->co, v2->co); /* use for temp storage */
+	/* note, we could average the tangents of both loops,
+	 * for non flat ngons it will give a better direction */
+	cross_v3_v3v3(r_tangent, tvec, e_loop->f->no);
+	normalize_v3(r_tangent);
+}
+
+/**
+ * \brief BMESH VERT/EDGE ANGLE
+ *
+ * Calculates the angle a verts 2 edges.
+ *
+ * \returns the angle in radians
+ */
+float BM_vert_calc_edge_angle_ex(const BMVert *v, const float fallback)
+{
+	BMEdge *e1, *e2;
+
+	/* saves BM_vert_edge_count(v) and and edge iterator,
+	 * get the edges and count them both at once */
+
+	if ((e1 = v->e) &&
+	    (e2 =  bmesh_disk_edge_next(e1, v)) &&
+	    (e1 != e2) &&
+	    /* make sure we come full circle and only have 2 connected edges */
+	    (e1 == bmesh_disk_edge_next(e2, v)))
+	{
+		BMVert *v1 = BM_edge_other_vert(e1, v);
+		BMVert *v2 = BM_edge_other_vert(e2, v);
+
+		return (float)M_PI - angle_v3v3v3(v1->co, v->co, v2->co);
+	}
+	else {
+		return fallback;
+	}
+}
+
+float BM_vert_calc_edge_angle(const BMVert *v)
+{
+	return BM_vert_calc_edge_angle_ex(v, DEG2RADF(90.0f));
+}
+
+/**
+ * \note this isn't optimal to run on an array of verts,
+ * see 'solidify_add_thickness' for a function which runs on an array.
+ */
+float BM_vert_calc_shell_factor(const BMVert *v)
+{
+	BMIter iter;
+	BMLoop *l;
+	float accum_shell = 0.0f;
+	float accum_angle = 0.0f;
+
+	BM_ITER_ELEM (l, &iter, (BMVert *)v, BM_LOOPS_OF_VERT) {
+		const float face_angle = BM_loop_calc_face_angle(l);
+		accum_shell += shell_v3v3_normalized_to_dist(v->no, l->f->no) * face_angle;
+		accum_angle += face_angle;
+	}
+
+	if (accum_angle != 0.0f) {
+		return accum_shell / accum_angle;
+	}
+	else {
+		return 1.0f;
+	}
+}
+/* alternate version of #BM_vert_calc_shell_factor which only
+ * uses 'hflag' faces, but falls back to all if none found. */
+float BM_vert_calc_shell_factor_ex(const BMVert *v, const float no[3], const char hflag)
+{
+	BMIter iter;
+	const BMLoop *l;
+	float accum_shell = 0.0f;
+	float accum_angle = 0.0f;
+	int tot_sel = 0, tot = 0;
+
+	BM_ITER_ELEM (l, &iter, (BMVert *)v, BM_LOOPS_OF_VERT) {
+		if (BM_elem_flag_test(l->f, hflag)) {  /* <-- main difference to BM_vert_calc_shell_factor! */
+			const float face_angle = BM_loop_calc_face_angle(l);
+			accum_shell += shell_v3v3_normalized_to_dist(no, l->f->no) * face_angle;
+			accum_angle += face_angle;
+			tot_sel++;
+		}
+		tot++;
+	}
+
+	if (accum_angle != 0.0f) {
+		return accum_shell / accum_angle;
+	}
+	else {
+		/* other main difference from BM_vert_calc_shell_factor! */
+		if (tot != 0 && tot_sel == 0) {
+			/* none selected, so use all */
+			return BM_vert_calc_shell_factor(v);
+		}
+		else {
+			return 1.0f;
+		}
+	}
+}
+
+/**
+ * \note quite an obscure function.
+ * used in bmesh operators that have a relative scale options,
+ */
+float BM_vert_calc_mean_tagged_edge_length(const BMVert *v)
+{
+	BMIter iter;
+	BMEdge *e;
+	int tot;
+	float length = 0.0f;
+
+	BM_ITER_ELEM_INDEX (e, &iter, (BMVert *)v, BM_EDGES_OF_VERT, tot) {
+		const BMVert *v_other = BM_edge_other_vert(e, v);
+		if (BM_elem_flag_test(v_other, BM_ELEM_TAG)) {
+			length += BM_edge_calc_length(e);
+		}
+	}
+
+	if (tot) {
+		return length / (float)tot;
+	}
+	else {
+		return 0.0f;
+	}
+}
+
+
+/**
+ * Returns the loop of the shortest edge in f.
+ */
+BMLoop *BM_face_find_shortest_loop(BMFace *f)
+{
+	BMLoop *shortest_loop = NULL;
+	float shortest_len = FLT_MAX;
+
+	BMLoop *l_iter;
+	BMLoop *l_first;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+
+	do {
+		const float len_sq = len_squared_v3v3(l_iter->v->co, l_iter->next->v->co);
+		if (len_sq <= shortest_len) {
+			shortest_loop = l_iter;
+			shortest_len = len_sq;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+
+	return shortest_loop;
+}
+
+/**
+ * Returns the loop of the longest edge in f.
+ */
+BMLoop *BM_face_find_longest_loop(BMFace *f)
+{
+	BMLoop *longest_loop = NULL;
+	float len_max_sq = 0.0f;
+
+	BMLoop *l_iter;
+	BMLoop *l_first;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+
+	do {
+		const float len_sq = len_squared_v3v3(l_iter->v->co, l_iter->next->v->co);
+		if (len_sq >= len_max_sq) {
+			longest_loop = l_iter;
+			len_max_sq = len_sq;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+
+	return longest_loop;
+}
+
+/**
+ * Returns the edge existing between \a v_a and \a v_b, or NULL if there isn't one.
+ *
+ * \note multiple edges may exist between any two vertices, and therefore
+ * this function only returns the first one found.
+ */
+#if 0
+BMEdge *BM_edge_exists(BMVert *v_a, BMVert *v_b)
+{
+	BMIter iter;
+	BMEdge *e;
+
+
+	BLI_assert(v_a != v_b);
+	BLI_assert(v_a->head.htype == BM_VERT && v_b->head.htype == BM_VERT);
+
+	BM_ITER_ELEM (e, &iter, v_a, BM_EDGES_OF_VERT) {
+		if (e->v1 == v_b || e->v2 == v_b)
+			return e;
+	}
+
+	return NULL;
+}
+#else
+BMEdge *BM_edge_exists(BMVert *v_a, BMVert *v_b)
+{
+	/* speedup by looping over both edges verts
+	 * where one vert may connect to many edges but not the other. */
+
+	BMEdge *e_a, *e_b;
+
+	BLI_assert(v_a != v_b);
+	BLI_assert(v_a->head.htype == BM_VERT && v_b->head.htype == BM_VERT);
+
+	if ((e_a = v_a->e) && (e_b = v_b->e)) {
+		BMEdge *e_a_iter = e_a, *e_b_iter = e_b;
+
+		do {
+			if (BM_vert_in_edge(e_a_iter, v_b)) {
+				return e_a_iter;
+			}
+			if (BM_vert_in_edge(e_b_iter, v_a)) {
+				return e_b_iter;
+			}
+		} while (((e_a_iter = bmesh_disk_edge_next(e_a_iter, v_a)) != e_a) &&
+		         ((e_b_iter = bmesh_disk_edge_next(e_b_iter, v_b)) != e_b));
+	}
+
+	return NULL;
+}
+#endif
+
+/**
+ * Returns an edge sharing the same vertices as this one.
+ * This isn't an invalid state but tools should clean up these cases before
+ * returning the mesh to the user.
+ */
+BMEdge *BM_edge_find_double(BMEdge *e)
+{
+	BMVert *v       = e->v1;
+	BMVert *v_other = e->v2;
+
+	BMEdge *e_iter;
+
+	e_iter = e;
+	while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e) {
+		if (UNLIKELY(BM_vert_in_edge(e_iter, v_other))) {
+			return e_iter;
+		}
+	}
+
+	return NULL;
+}
+
+/**
+ * Given a set of vertices (varr), find out if
+ * there is a face with exactly those vertices
+ * (and only those vertices).
+ *
+ * \note there used to be a BM_face_exists_overlap function that checks for partial overlap.
+ */
+BMFace *BM_face_exists(BMVert **varr, int len)
+{
+	if (varr[0]->e) {
+		BMEdge *e_iter, *e_first;
+		e_iter = e_first = varr[0]->e;
+
+		/* would normally use BM_LOOPS_OF_VERT, but this runs so often,
+		 * its faster to iterate on the data directly */
+		do {
+			if (e_iter->l) {
+				BMLoop *l_iter_radial, *l_first_radial;
+				l_iter_radial = l_first_radial = e_iter->l;
+
+				do {
+					if ((l_iter_radial->v == varr[0]) &&
+					    (l_iter_radial->f->len == len))
+					{
+						/* the fist 2 verts match, now check the remaining (len - 2) faces do too
+						 * winding isn't known, so check in both directions */
+						int i_walk = 2;
+
+						if (l_iter_radial->next->v == varr[1]) {
+							BMLoop *l_walk = l_iter_radial->next->next;
+							do {
+								if (l_walk->v != varr[i_walk]) {
+									break;
+								}
+							} while ((void)(l_walk = l_walk->next), ++i_walk != len);
+						}
+						else if (l_iter_radial->prev->v == varr[1]) {
+							BMLoop *l_walk = l_iter_radial->prev->prev;
+							do {
+								if (l_walk->v != varr[i_walk]) {
+									break;
+								}
+							} while ((void)(l_walk = l_walk->prev), ++i_walk != len);
+						}
+
+						if (i_walk == len) {
+							return l_iter_radial->f;
+						}
+					}
+				} while ((l_iter_radial = l_iter_radial->radial_next) != l_first_radial);
+
+			}
+		} while ((e_iter = BM_DISK_EDGE_NEXT(e_iter, varr[0])) != e_first);
+	}
+
+	return NULL;
+}
+
+
+/**
+ * Given a set of vertices and edges (\a varr, \a earr), find out if
+ * all those vertices are filled in by existing faces that _only_ use those vertices.
+ *
+ * This is for use in cases where creating a face is possible but would result in
+ * many overlapping faces.
+ *
+ * An example of how this is used: when 2 tri's are selected that share an edge,
+ * pressing Fkey would make a new overlapping quad (without a check like this)
+ *
+ * \a earr and \a varr can be in any order, however they _must_ form a closed loop.
+ */
+bool BM_face_exists_multi(BMVert **varr, BMEdge **earr, int len)
+{
+	BMFace *f;
+	BMEdge *e;
+	BMVert *v;
+	bool ok;
+	int tot_tag;
+
+	BMIter fiter;
+	BMIter viter;
+
+	int i;
+
+	for (i = 0; i < len; i++) {
+		/* save some time by looping over edge faces rather then vert faces
+		 * will still loop over some faces twice but not as many */
+		BM_ITER_ELEM (f, &fiter, earr[i], BM_FACES_OF_EDGE) {
+			BM_elem_flag_disable(f, BM_ELEM_INTERNAL_TAG);
+			BM_ITER_ELEM (v, &viter, f, BM_VERTS_OF_FACE) {
+				BM_elem_flag_disable(v, BM_ELEM_INTERNAL_TAG);
+			}
+		}
+
+		/* clear all edge tags */
+		BM_ITER_ELEM (e, &fiter, varr[i], BM_EDGES_OF_VERT) {
+			BM_elem_flag_disable(e, BM_ELEM_INTERNAL_TAG);
+		}
+	}
+
+	/* now tag all verts and edges in the boundary array as true so
+	 * we can know if a face-vert is from our array */
+	for (i = 0; i < len; i++) {
+		BM_elem_flag_enable(varr[i], BM_ELEM_INTERNAL_TAG);
+		BM_elem_flag_enable(earr[i], BM_ELEM_INTERNAL_TAG);
+	}
+
+
+	/* so! boundary is tagged, everything else cleared */
+
+
+	/* 1) tag all faces connected to edges - if all their verts are boundary */
+	tot_tag = 0;
+	for (i = 0; i < len; i++) {
+		BM_ITER_ELEM (f, &fiter, earr[i], BM_FACES_OF_EDGE) {
+			if (!BM_elem_flag_test(f, BM_ELEM_INTERNAL_TAG)) {
+				ok = true;
+				BM_ITER_ELEM (v, &viter, f, BM_VERTS_OF_FACE) {
+					if (!BM_elem_flag_test(v, BM_ELEM_INTERNAL_TAG)) {
+						ok = false;
+						break;
+					}
+				}
+
+				if (ok) {
+					/* we only use boundary verts */
+					BM_elem_flag_enable(f, BM_ELEM_INTERNAL_TAG);
+					tot_tag++;
+				}
+			}
+			else {
+				/* we already found! */
+			}
+		}
+	}
+
+	if (tot_tag == 0) {
+		/* no faces use only boundary verts, quit early */
+		ok = false;
+		goto finally;
+	}
+
+	/* 2) loop over non-boundary edges that use boundary verts,
+	 *    check each have 2 tagged faces connected (faces that only use 'varr' verts) */
+	ok = true;
+	for (i = 0; i < len; i++) {
+		BM_ITER_ELEM (e, &fiter, varr[i], BM_EDGES_OF_VERT) {
+
+			if (/* non-boundary edge */
+			    BM_elem_flag_test(e, BM_ELEM_INTERNAL_TAG) == false &&
+			    /* ...using boundary verts */
+			    BM_elem_flag_test(e->v1, BM_ELEM_INTERNAL_TAG) &&
+			    BM_elem_flag_test(e->v2, BM_ELEM_INTERNAL_TAG))
+			{
+				int tot_face_tag = 0;
+				BM_ITER_ELEM (f, &fiter, e, BM_FACES_OF_EDGE) {
+					if (BM_elem_flag_test(f, BM_ELEM_INTERNAL_TAG)) {
+						tot_face_tag++;
+					}
+				}
+
+				if (tot_face_tag != 2) {
+					ok = false;
+					break;
+				}
+
+			}
+		}
+
+		if (ok == false) {
+			break;
+		}
+	}
+
+finally:
+	/* Cleanup */
+	for (i = 0; i < len; i++) {
+		BM_elem_flag_disable(varr[i], BM_ELEM_INTERNAL_TAG);
+		BM_elem_flag_disable(earr[i], BM_ELEM_INTERNAL_TAG);
+	}
+	return ok;
+}
+
+/* same as 'BM_face_exists_multi' but built vert array from edges */
+bool BM_face_exists_multi_edge(BMEdge **earr, int len)
+{
+	BMVert **varr = BLI_array_alloca(varr, len);
+
+	/* first check if verts have edges, if not we can bail out early */
+	if (!BM_verts_from_edges(varr, earr, len)) {
+		BMESH_ASSERT(0);
+		return false;
+	}
+
+	return BM_face_exists_multi(varr, earr, len);
+}
+
+
+/**
+ * Given a set of vertices (varr), find out if
+ * all those vertices overlap an existing face.
+ *
+ * \note The face may contain other verts \b not in \a varr.
+ *
+ * \note Its possible there are more than one overlapping faces,
+ * in this case the first one found will be returned.
+ *
+ * \param varr  Array of unordered verts.
+ * \param len  \a varr array length.
+ * \return The face or NULL.
+ */
+
+BMFace *BM_face_exists_overlap(BMVert **varr, const int len)
+{
+	BMIter viter;
+	BMFace *f;
+	int i;
+	BMFace *f_overlap = NULL;
+	LinkNode *f_lnk = NULL;
+
+#ifdef DEBUG
+	/* check flag isn't already set */
+	for (i = 0; i < len; i++) {
+		BM_ITER_ELEM (f, &viter, varr[i], BM_FACES_OF_VERT) {
+			BLI_assert(BM_ELEM_API_FLAG_TEST(f, _FLAG_OVERLAP) == 0);
+		}
+	}
+#endif
+
+	for (i = 0; i < len; i++) {
+		BM_ITER_ELEM (f, &viter, varr[i], BM_FACES_OF_VERT) {
+			if (BM_ELEM_API_FLAG_TEST(f, _FLAG_OVERLAP) == 0) {
+				if (len <= BM_verts_in_face_count(varr, len, f)) {
+					f_overlap = f;
+					break;
+				}
+
+				BM_ELEM_API_FLAG_ENABLE(f, _FLAG_OVERLAP);
+				BLI_linklist_prepend_alloca(&f_lnk, f);
+			}
+		}
+	}
+
+	for (; f_lnk; f_lnk = f_lnk->next) {
+		BM_ELEM_API_FLAG_DISABLE((BMFace *)f_lnk->link, _FLAG_OVERLAP);
+	}
+
+	return f_overlap;
+}
+
+/**
+ * Given a set of vertices (varr), find out if
+ * there is a face that uses vertices only from this list
+ * (that the face is a subset or made from the vertices given).
+ *
+ * \param varr  Array of unordered verts.
+ * \param len  varr array length.
+ */
+bool BM_face_exists_overlap_subset(BMVert **varr, const int len)
+{
+	BMIter viter;
+	BMFace *f;
+	bool is_init = false;
+	bool is_overlap = false;
+	LinkNode *f_lnk = NULL;
+
+#ifdef DEBUG
+	/* check flag isn't already set */
+	for (int i = 0; i < len; i++) {
+		BLI_assert(BM_ELEM_API_FLAG_TEST(varr[i], _FLAG_OVERLAP) == 0);
+		BM_ITER_ELEM (f, &viter, varr[i], BM_FACES_OF_VERT) {
+			BLI_assert(BM_ELEM_API_FLAG_TEST(f, _FLAG_OVERLAP) == 0);
+		}
+	}
+#endif
+
+	for (int i = 0; i < len; i++) {
+		BM_ITER_ELEM (f, &viter, varr[i], BM_FACES_OF_VERT) {
+			if ((f->len <= len) && (BM_ELEM_API_FLAG_TEST(f, _FLAG_OVERLAP) == 0)) {
+				/* check if all vers in this face are flagged*/
+				BMLoop *l_iter, *l_first;
+
+				if (is_init == false) {
+					is_init = true;
+					for (int j = 0; j < len; j++) {
+						BM_ELEM_API_FLAG_ENABLE(varr[j], _FLAG_OVERLAP);
+					}
+				}
+
+				l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+				is_overlap = true;
+				do {
+					if (BM_ELEM_API_FLAG_TEST(l_iter->v, _FLAG_OVERLAP) == 0) {
+						is_overlap = false;
+						break;
+					}
+				} while ((l_iter = l_iter->next) != l_first);
+
+				if (is_overlap) {
+					break;
+				}
+
+				BM_ELEM_API_FLAG_ENABLE(f, _FLAG_OVERLAP);
+				BLI_linklist_prepend_alloca(&f_lnk, f);
+			}
+		}
+	}
+
+	if (is_init == true) {
+		for (int i = 0; i < len; i++) {
+			BM_ELEM_API_FLAG_DISABLE(varr[i], _FLAG_OVERLAP);
+		}
+	}
+
+	for (; f_lnk; f_lnk = f_lnk->next) {
+		BM_ELEM_API_FLAG_DISABLE((BMFace *)f_lnk->link, _FLAG_OVERLAP);
+	}
+
+	return is_overlap;
+}
+
+bool BM_vert_is_all_edge_flag_test(const BMVert *v, const char hflag, const bool respect_hide)
+{
+	if (v->e) {
+		BMEdge *e_other;
+		BMIter eiter;
+
+		BM_ITER_ELEM (e_other, &eiter, (BMVert *)v, BM_EDGES_OF_VERT) {
+			if (!respect_hide || !BM_elem_flag_test(e_other, BM_ELEM_HIDDEN)) {
+				if (!BM_elem_flag_test(e_other, hflag)) {
+					return false;
+				}
+			}
+		}
+	}
+
+	return true;
+}
+
+bool BM_vert_is_all_face_flag_test(const BMVert *v, const char hflag, const bool respect_hide)
+{
+	if (v->e) {
+		BMEdge *f_other;
+		BMIter fiter;
+
+		BM_ITER_ELEM (f_other, &fiter, (BMVert *)v, BM_FACES_OF_VERT) {
+			if (!respect_hide || !BM_elem_flag_test(f_other, BM_ELEM_HIDDEN)) {
+				if (!BM_elem_flag_test(f_other, hflag)) {
+					return false;
+				}
+			}
+		}
+	}
+
+	return true;
+}
+
+
+bool BM_edge_is_all_face_flag_test(const BMEdge *e, const char hflag, const bool respect_hide)
+{
+	if (e->l) {
+		BMLoop *l_iter, *l_first;
+
+		l_iter = l_first = e->l;
+		do {
+			if (!respect_hide || !BM_elem_flag_test(l_iter->f, BM_ELEM_HIDDEN)) {
+				if (!BM_elem_flag_test(l_iter->f, hflag)) {
+					return false;
+				}
+			}
+		} while ((l_iter = l_iter->radial_next) != l_first);
+	}
+
+	return true;
+}
+
+/* convenience functions for checking flags */
+bool BM_edge_is_any_vert_flag_test(const BMEdge *e, const char hflag)
+{
+	return (BM_elem_flag_test(e->v1, hflag) ||
+	        BM_elem_flag_test(e->v2, hflag));
+}
+
+bool BM_face_is_any_vert_flag_test(const BMFace *f, const char hflag)
+{
+	BMLoop *l_iter;
+	BMLoop *l_first;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+	do {
+		if (BM_elem_flag_test(l_iter->v, hflag)) {
+			return true;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+	return false;
+}
+
+bool BM_face_is_any_edge_flag_test(const BMFace *f, const char hflag)
+{
+	BMLoop *l_iter;
+	BMLoop *l_first;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+	do {
+		if (BM_elem_flag_test(l_iter->e, hflag)) {
+			return true;
+		}
+	} while ((l_iter = l_iter->next) != l_first);
+	return false;
+}
+
+/**
+ * Use within assert's to check normals are valid.
+ */
+bool BM_face_is_normal_valid(const BMFace *f)
+{
+	const float eps = 0.0001f;
+	float no[3];
+
+	BM_face_calc_normal(f, no);
+	return len_squared_v3v3(no, f->no) < (eps * eps);
+}
+
+static void bm_mesh_calc_volume_face(const BMFace *f, float *r_vol)
+{
+	const int tottri = f->len - 2;
+	BMLoop **loops = BLI_array_alloca(loops, f->len);
+	uint (*index)[3] = BLI_array_alloca(index, tottri);
+	int j;
+
+	BM_face_calc_tessellation(f, false, loops, index);
+
+	for (j = 0; j < tottri; j++) {
+		const float *p1 = loops[index[j][0]]->v->co;
+		const float *p2 = loops[index[j][1]]->v->co;
+		const float *p3 = loops[index[j][2]]->v->co;
+
+		/* co1.dot(co2.cross(co3)) / 6.0 */
+		float cross[3];
+		cross_v3_v3v3(cross, p2, p3);
+		*r_vol += (1.0f / 6.0f) * dot_v3v3(p1, cross);
+	}
+}
+float BM_mesh_calc_volume(BMesh *bm, bool is_signed)
+{
+	/* warning, calls own tessellation function, may be slow */
+	float vol = 0.0f;
+	BMFace *f;
+	BMIter fiter;
+
+	BM_ITER_MESH (f, &fiter, bm, BM_FACES_OF_MESH) {
+		bm_mesh_calc_volume_face(f, &vol);
+	}
+
+	if (is_signed == false) {
+		vol = fabsf(vol);
+	}
+
+	return vol;
+}
+
+/* note, almost duplicate of BM_mesh_calc_edge_groups, keep in sync */
+/**
+ * Calculate isolated groups of faces with optional filtering.
+ *
+ * \param bm  the BMesh.
+ * \param r_groups_array  Array of ints to fill in, length of bm->totface
+ *        (or when hflag_test is set, the number of flagged faces).
+ * \param r_group_index  index, length pairs into \a r_groups_array, size of return value
+ *        int pairs: (array_start, array_length).
+ * \param filter_fn  Filter the edge-loops or vert-loops we step over (depends on \a htype_step).
+ * \param user_data  Optional user data for \a filter_fn, can be NULL.
+ * \param hflag_test  Optional flag to test faces,
+ *        use to exclude faces from the calculation, 0 for all faces.
+ * \param htype_step  BM_VERT to walk over face-verts, BM_EDGE to walk over faces edges
+ *        (having both set is supported too).
+ * \return The number of groups found.
+ */
+int BM_mesh_calc_face_groups(
+        BMesh *bm, int *r_groups_array, int (**r_group_index)[2],
+        BMLoopFilterFunc filter_fn, void *user_data,
+        const char hflag_test, const char htype_step)
+{
+#ifdef DEBUG
+	int group_index_len = 1;
+#else
+	int group_index_len = 32;
+#endif
+
+	int (*group_index)[2] = MEM_mallocN(sizeof(*group_index) * group_index_len, __func__);
+
+	int *group_array = r_groups_array;
+	STACK_DECLARE(group_array);
+
+	int group_curr = 0;
+
+	uint tot_faces = 0;
+	uint tot_touch = 0;
+
+	BMFace **stack;
+	STACK_DECLARE(stack);
+
+	BMIter iter;
+	BMFace *f;
+	int i;
+
+	STACK_INIT(group_array, bm->totface);
+
+	BLI_assert(((htype_step & ~(BM_VERT | BM_EDGE)) == 0) && (htype_step != 0));
+
+	/* init the array */
+	BM_ITER_MESH_INDEX (f, &iter, bm, BM_FACES_OF_MESH, i) {
+		if ((hflag_test == 0) || BM_elem_flag_test(f, hflag_test)) {
+			tot_faces++;
+			BM_elem_flag_disable(f, BM_ELEM_TAG);
+		}
+		else {
+			/* never walk over tagged */
+			BM_elem_flag_enable(f, BM_ELEM_TAG);
+		}
+
+		BM_elem_index_set(f, i); /* set_inline */
+	}
+	bm->elem_index_dirty &= ~BM_FACE;
+
+	/* detect groups */
+	stack = MEM_mallocN(sizeof(*stack) * tot_faces, __func__);
+
+	while (tot_touch != tot_faces) {
+		int *group_item;
+		bool ok = false;
+
+		BLI_assert(tot_touch < tot_faces);
+
+		STACK_INIT(stack, tot_faces);
+
+		BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
+			if (BM_elem_flag_test(f, BM_ELEM_TAG) == false) {
+				BM_elem_flag_enable(f, BM_ELEM_TAG);
+				STACK_PUSH(stack, f);
+				ok = true;
+				break;
+			}
+		}
+
+		BLI_assert(ok == true);
+		UNUSED_VARS_NDEBUG(ok);
+
+		/* manage arrays */
+		if (group_index_len == group_curr) {
+			group_index_len *= 2;
+			group_index = MEM_reallocN(group_index, sizeof(*group_index) * group_index_len);
+		}
+
+		group_item = group_index[group_curr];
+		group_item[0] = STACK_SIZE(group_array);
+		group_item[1] = 0;
+
+		while ((f = STACK_POP(stack))) {
+			BMLoop *l_iter, *l_first;
+
+			/* add face */
+			STACK_PUSH(group_array, BM_elem_index_get(f));
+			tot_touch++;
+			group_item[1]++;
+			/* done */
+
+			if (htype_step & BM_EDGE) {
+				/* search for other faces */
+				l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+				do {
+					BMLoop *l_radial_iter = l_iter->radial_next;
+					if ((l_radial_iter != l_iter) &&
+					    ((filter_fn == NULL) || filter_fn(l_iter, user_data)))
+					{
+						do {
+							BMFace *f_other = l_radial_iter->f;
+							if (BM_elem_flag_test(f_other, BM_ELEM_TAG) == false) {
+								BM_elem_flag_enable(f_other, BM_ELEM_TAG);
+								STACK_PUSH(stack, f_other);
+							}
+						} while ((l_radial_iter = l_radial_iter->radial_next) != l_iter);
+					}
+				} while ((l_iter = l_iter->next) != l_first);
+			}
+
+			if (htype_step & BM_VERT) {
+				BMIter liter;
+				/* search for other faces */
+				l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+				do {
+					if ((filter_fn == NULL) || filter_fn(l_iter, user_data)) {
+						BMLoop *l_other;
+						BM_ITER_ELEM (l_other, &liter, l_iter, BM_LOOPS_OF_LOOP) {
+							BMFace *f_other = l_other->f;
+							if (BM_elem_flag_test(f_other, BM_ELEM_TAG) == false) {
+								BM_elem_flag_enable(f_other, BM_ELEM_TAG);
+								STACK_PUSH(stack, f_other);
+							}
+						}
+					}
+				} while ((l_iter = l_iter->next) != l_first);
+			}
+		}
+
+		group_curr++;
+	}
+
+	MEM_freeN(stack);
+
+	/* reduce alloc to required size */
+	group_index = MEM_reallocN(group_index, sizeof(*group_index) * group_curr);
+	*r_group_index = group_index;
+
+	return group_curr;
+}
+
+/* note, almost duplicate of BM_mesh_calc_face_groups, keep in sync */
+/**
+ * Calculate isolated groups of edges with optional filtering.
+ *
+ * \param bm  the BMesh.
+ * \param r_groups_array  Array of ints to fill in, length of bm->totedge
+ *        (or when hflag_test is set, the number of flagged edges).
+ * \param r_group_index  index, length pairs into \a r_groups_array, size of return value
+ *        int pairs: (array_start, array_length).
+ * \param filter_fn  Filter the edges or verts we step over (depends on \a htype_step)
+ *        as to which types we deal with.
+ * \param user_data  Optional user data for \a filter_fn, can be NULL.
+ * \param hflag_test  Optional flag to test edges,
+ *        use to exclude edges from the calculation, 0 for all edges.
+ * \return The number of groups found.
+ *
+ * \note Unlike #BM_mesh_calc_face_groups there is no 'htype_step' argument,
+ *       since we always walk over verts.
+ */
+int BM_mesh_calc_edge_groups(
+        BMesh *bm, int *r_groups_array, int (**r_group_index)[2],
+        BMVertFilterFunc filter_fn, void *user_data,
+        const char hflag_test)
+{
+#ifdef DEBUG
+	int group_index_len = 1;
+#else
+	int group_index_len = 32;
+#endif
+
+	int (*group_index)[2] = MEM_mallocN(sizeof(*group_index) * group_index_len, __func__);
+
+	int *group_array = r_groups_array;
+	STACK_DECLARE(group_array);
+
+	int group_curr = 0;
+
+	uint tot_edges = 0;
+	uint tot_touch = 0;
+
+	BMEdge **stack;
+	STACK_DECLARE(stack);
+
+	BMIter iter;
+	BMEdge *e;
+	int i;
+
+	STACK_INIT(group_array, bm->totedge);
+
+	/* init the array */
+	BM_ITER_MESH_INDEX (e, &iter, bm, BM_EDGES_OF_MESH, i) {
+		if ((hflag_test == 0) || BM_elem_flag_test(e, hflag_test)) {
+			tot_edges++;
+			BM_elem_flag_disable(e, BM_ELEM_TAG);
+		}
+		else {
+			/* never walk over tagged */
+			BM_elem_flag_enable(e, BM_ELEM_TAG);
+		}
+
+		BM_elem_index_set(e, i); /* set_inline */
+	}
+	bm->elem_index_dirty &= ~BM_EDGE;
+
+	/* detect groups */
+	stack = MEM_mallocN(sizeof(*stack) * tot_edges, __func__);
+
+	while (tot_touch != tot_edges) {
+		int *group_item;
+		bool ok = false;
+
+		BLI_assert(tot_touch < tot_edges);
+
+		STACK_INIT(stack, tot_edges);
+
+		BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
+			if (BM_elem_flag_test(e, BM_ELEM_TAG) == false) {
+				BM_elem_flag_enable(e, BM_ELEM_TAG);
+				STACK_PUSH(stack, e);
+				ok = true;
+				break;
+			}
+		}
+
+		BLI_assert(ok == true);
+		UNUSED_VARS_NDEBUG(ok);
+
+		/* manage arrays */
+		if (group_index_len == group_curr) {
+			group_index_len *= 2;
+			group_index = MEM_reallocN(group_index, sizeof(*group_index) * group_index_len);
+		}
+
+		group_item = group_index[group_curr];
+		group_item[0] = STACK_SIZE(group_array);
+		group_item[1] = 0;
+
+		while ((e = STACK_POP(stack))) {
+			BMIter viter;
+			BMIter eiter;
+			BMVert *v;
+
+			/* add edge */
+			STACK_PUSH(group_array, BM_elem_index_get(e));
+			tot_touch++;
+			group_item[1]++;
+			/* done */
+
+			/* search for other edges */
+			BM_ITER_ELEM (v, &viter, e, BM_VERTS_OF_EDGE) {
+				if ((filter_fn == NULL) || filter_fn(v, user_data)) {
+					BMEdge *e_other;
+					BM_ITER_ELEM (e_other, &eiter, v, BM_EDGES_OF_VERT) {
+						if (BM_elem_flag_test(e_other, BM_ELEM_TAG) == false) {
+							BM_elem_flag_enable(e_other, BM_ELEM_TAG);
+							STACK_PUSH(stack, e_other);
+						}
+					}
+				}
+			}
+		}
+
+		group_curr++;
+	}
+
+	MEM_freeN(stack);
+
+	/* reduce alloc to required size */
+	group_index = MEM_reallocN(group_index, sizeof(*group_index) * group_curr);
+	*r_group_index = group_index;
+
+	return group_curr;
+}
+
+float bmesh_subd_falloff_calc(const int falloff, float val)
+{
+	switch (falloff) {
+		case SUBD_FALLOFF_SMOOTH:
+			val = 3.0f * val * val - 2.0f * val * val * val;
+			break;
+		case SUBD_FALLOFF_SPHERE:
+			val = sqrtf(2.0f * val - val * val);
+			break;
+		case SUBD_FALLOFF_ROOT:
+			val = sqrtf(val);
+			break;
+		case SUBD_FALLOFF_SHARP:
+			val = val * val;
+			break;
+		case SUBD_FALLOFF_LIN:
+			break;
+		case SUBD_FALLOFF_INVSQUARE:
+			val = val * (2.0f - val);
+			break;
+		default:
+			BLI_assert(0);
+			break;
+	}
+
+	return val;
+}