/*
 * ***** 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.
 *
 * The Original Code is Copyright (C) 2005 by the Blender Foundation.
 * All rights reserved.
 *
 * Contributor(s): Campbell Barton
 *                 Shinsuke Irie
 *                 Martin Felke
 *
 * ***** END GPL LICENSE BLOCK *****
 *
 */

/** \file blender/modifiers/intern/MOD_solidify.c
 *  \ingroup modifiers
 */

#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"

#include "MEM_guardedalloc.h"

#include "BLI_utildefines.h"
#include "BLI_stackdefines.h"
#include "BLI_bitmap.h"
#include "BLI_math.h"

#include "BKE_cdderivedmesh.h"
#include "BKE_mesh.h"
#include "BKE_particle.h"
#include "BKE_deform.h"

#include "MOD_modifiertypes.h"
#include "MOD_util.h"

#ifdef __GNUC__
#  pragma GCC diagnostic error "-Wsign-conversion"
#endif

/* skip shell thickness for non-manifold edges, see [#35710] */
#define USE_NONMANIFOLD_WORKAROUND

/* *** derived mesh high quality normal calculation function  *** */
/* could be exposed for other functions to use */

typedef struct EdgeFaceRef {
	int f1; /* init as -1 */
	int f2;
} EdgeFaceRef;

BLI_INLINE bool edgeref_is_init(const EdgeFaceRef *edge_ref)
{
	return !((edge_ref->f1 == 0) && (edge_ref->f2 == 0));
}

/**
 * \param dm  Mesh to calculate normals for.
 * \param face_nors  Precalculated face normals.
 * \param r_vert_nors  Return vert normals.
 */
static void dm_calc_normal(DerivedMesh *dm, float (*face_nors)[3], float (*r_vert_nors)[3])
{
	int i, numVerts, numEdges, numFaces;
	MPoly *mpoly, *mp;
	MLoop *mloop, *ml;
	MEdge *medge, *ed;
	MVert *mvert, *mv;

	numVerts = dm->getNumVerts(dm);
	numEdges = dm->getNumEdges(dm);
	numFaces = dm->getNumPolys(dm);
	mpoly = dm->getPolyArray(dm);
	medge = dm->getEdgeArray(dm);
	mvert = dm->getVertArray(dm);
	mloop = dm->getLoopArray(dm);

	/* we don't want to overwrite any referenced layers */

	/* Doesn't work here! */
#if 0
	mv = CustomData_duplicate_referenced_layer(&dm->vertData, CD_MVERT, numVerts);
	cddm->mvert = mv;
#endif

	mv = mvert;
	mp = mpoly;

	{
		EdgeFaceRef *edge_ref_array = MEM_callocN(sizeof(EdgeFaceRef) * (size_t)numEdges, "Edge Connectivity");
		EdgeFaceRef *edge_ref;
		float edge_normal[3];

		/* This loop adds an edge hash if its not there, and adds the face index */
		for (i = 0; i < numFaces; i++, mp++) {
			int j;

			ml = mloop + mp->loopstart;

			for (j = 0; j < mp->totloop; j++, ml++) {
				/* --- add edge ref to face --- */
				edge_ref = &edge_ref_array[ml->e];
				if (!edgeref_is_init(edge_ref)) {
					edge_ref->f1 =  i;
					edge_ref->f2 = -1;
				}
				else if ((edge_ref->f1 != -1) && (edge_ref->f2 == -1)) {
					edge_ref->f2 = i;
				}
				else {
					/* 3+ faces using an edge, we can't handle this usefully */
					edge_ref->f1 = edge_ref->f2 = -1;
#ifdef USE_NONMANIFOLD_WORKAROUND
					medge[ml->e].flag |= ME_EDGE_TMP_TAG;
#endif
				}
				/* --- done --- */
			}
		}

		for (i = 0, ed = medge, edge_ref = edge_ref_array; i < numEdges; i++, ed++, edge_ref++) {
			/* Get the edge vert indices, and edge value (the face indices that use it) */

			if (edgeref_is_init(edge_ref) && (edge_ref->f1 != -1)) {
				if (edge_ref->f2 != -1) {
					/* We have 2 faces using this edge, calculate the edges normal
					 * using the angle between the 2 faces as a weighting */
#if 0
					add_v3_v3v3(edge_normal, face_nors[edge_ref->f1], face_nors[edge_ref->f2]);
					normalize_v3(edge_normal);

					mul_v3_fl(edge_normal, angle_normalized_v3v3(face_nors[edge_ref->f1], face_nors[edge_ref->f2]));
#else
					mid_v3_v3v3_angle_weighted(edge_normal, face_nors[edge_ref->f1], face_nors[edge_ref->f2]);
#endif
				}
				else {
					/* only one face attached to that edge */
					/* an edge without another attached- the weight on this is undefined */
					copy_v3_v3(edge_normal, face_nors[edge_ref->f1]);
				}
				add_v3_v3(r_vert_nors[ed->v1], edge_normal);
				add_v3_v3(r_vert_nors[ed->v2], edge_normal);
			}
		}
		MEM_freeN(edge_ref_array);
	}

	/* normalize vertex normals and assign */
	for (i = 0; i < numVerts; i++, mv++) {
		if (normalize_v3(r_vert_nors[i]) == 0.0f) {
			normal_short_to_float_v3(r_vert_nors[i], mv->no);
		}
	}
}

static void initData(ModifierData *md)
{
	SolidifyModifierData *smd = (SolidifyModifierData *) md;
	smd->offset = 0.01f;
	smd->offset_fac = -1.0f;
	smd->flag = MOD_SOLIDIFY_RIM;
}

static void copyData(ModifierData *md, ModifierData *target)
{
#if 0
	SolidifyModifierData *smd = (SolidifyModifierData *) md;
	SolidifyModifierData *tsmd = (SolidifyModifierData *) target;
#endif
	modifier_copyData_generic(md, target);
}

static CustomDataMask requiredDataMask(Object *UNUSED(ob), ModifierData *md)
{
	SolidifyModifierData *smd = (SolidifyModifierData *) md;
	CustomDataMask dataMask = 0;

	/* ask for vertexgroups if we need them */
	if (smd->defgrp_name[0]) dataMask |= CD_MASK_MDEFORMVERT;

	return dataMask;
}

/* specific function for solidify - define locally */
BLI_INLINE void madd_v3v3short_fl(float r[3], const short a[3], const float f)
{
	r[0] += (float)a[0] * f;
	r[1] += (float)a[1] * f;
	r[2] += (float)a[2] * f;
}

static DerivedMesh *applyModifier(
        ModifierData *md, Object *ob,
        DerivedMesh *dm,
        ModifierApplyFlag UNUSED(flag))
{
	DerivedMesh *result;
	const SolidifyModifierData *smd = (SolidifyModifierData *) md;

	MVert *mv, *mvert, *orig_mvert;
	MEdge *ed, *medge, *orig_medge;
	MLoop *ml, *mloop, *orig_mloop;
	MPoly *mp, *mpoly, *orig_mpoly;
	const unsigned int numVerts = (unsigned int)dm->getNumVerts(dm);
	const unsigned int numEdges = (unsigned int)dm->getNumEdges(dm);
	const unsigned int numFaces = (unsigned int)dm->getNumPolys(dm);
	const unsigned int numLoops = (unsigned int)dm->getNumLoops(dm);
	unsigned int newLoops = 0, newFaces = 0, newEdges = 0, newVerts = 0, rimVerts = 0;

	/* only use material offsets if we have 2 or more materials  */
	const short mat_nr_max = ob->totcol > 1 ? ob->totcol - 1 : 0;
	const short mat_ofs = mat_nr_max ? smd->mat_ofs : 0;
	const short mat_ofs_rim = mat_nr_max ? smd->mat_ofs_rim : 0;

	/* use for edges */
	/* over-alloc new_vert_arr, old_vert_arr */
	unsigned int *new_vert_arr = NULL;
	STACK_DECLARE(new_vert_arr);

	unsigned int *new_edge_arr = NULL;
	STACK_DECLARE(new_edge_arr);

	unsigned int *old_vert_arr = MEM_callocN(sizeof(*old_vert_arr) * (size_t)numVerts, "old_vert_arr in solidify");

	unsigned int *edge_users = NULL;
	char *edge_order = NULL;

	float (*vert_nors)[3] = NULL;
	float (*face_nors)[3] = NULL;

	const bool need_face_normals = (smd->flag & MOD_SOLIDIFY_NORMAL_CALC) || (smd->flag & MOD_SOLIDIFY_EVEN);

	const float ofs_orig = -(((-smd->offset_fac + 1.0f) * 0.5f) * smd->offset);
	const float ofs_new  = smd->offset + ofs_orig;
	const float offset_fac_vg = smd->offset_fac_vg;
	const float offset_fac_vg_inv = 1.0f - smd->offset_fac_vg;
	const bool do_flip = (smd->flag & MOD_SOLIDIFY_FLIP) != 0;
	const bool do_clamp = (smd->offset_clamp != 0.0f);
	const bool do_shell = ((smd->flag & MOD_SOLIDIFY_RIM) && (smd->flag & MOD_SOLIDIFY_NOSHELL)) == 0;

	/* weights */
	MDeformVert *dvert;
	const bool defgrp_invert = (smd->flag & MOD_SOLIDIFY_VGROUP_INV) != 0;
	int defgrp_index;

	/* array size is doubled in case of using a shell */
	const unsigned int stride = do_shell ? 2 : 1;

	modifier_get_vgroup(ob, dm, smd->defgrp_name, &dvert, &defgrp_index);

	orig_mvert = dm->getVertArray(dm);
	orig_medge = dm->getEdgeArray(dm);
	orig_mloop = dm->getLoopArray(dm);
	orig_mpoly = dm->getPolyArray(dm);

	if (need_face_normals) {
		/* calculate only face normals */
		face_nors = MEM_mallocN(sizeof(*face_nors) * (size_t)numFaces, __func__);
		BKE_mesh_calc_normals_poly(
		            orig_mvert, (int)numVerts,
		            orig_mloop, orig_mpoly,
		            (int)numLoops, (int)numFaces,
		            face_nors, true);
	}

	STACK_INIT(new_vert_arr, numVerts * 2);
	STACK_INIT(new_edge_arr, numEdges * 2);

	if (smd->flag & MOD_SOLIDIFY_RIM) {
		BLI_bitmap *orig_mvert_tag = BLI_BITMAP_NEW(numVerts, __func__);
		unsigned int eidx;
		unsigned int i;

#define INVALID_UNUSED ((unsigned int)-1)
#define INVALID_PAIR ((unsigned int)-2)

		new_vert_arr = MEM_mallocN(sizeof(*new_vert_arr) * (size_t)(numVerts * 2), __func__);
		new_edge_arr = MEM_mallocN(sizeof(*new_edge_arr) * (size_t)((numEdges * 2) + numVerts), __func__);

		edge_users = MEM_mallocN(sizeof(*edge_users) * (size_t)numEdges, "solid_mod edges");
		edge_order = MEM_mallocN(sizeof(*edge_order) * (size_t)numEdges, "solid_mod eorder");


		/* save doing 2 loops here... */
#if 0
		copy_vn_i(edge_users, numEdges, INVALID_UNUSED);
#endif

		for (eidx = 0, ed = orig_medge; eidx < numEdges; eidx++, ed++) {
			edge_users[eidx] = INVALID_UNUSED;
		}

		for (i = 0, mp = orig_mpoly; i < numFaces; i++, mp++) {
			MLoop *ml_prev;
			int j;

			ml = orig_mloop + mp->loopstart;
			ml_prev = ml + (mp->totloop - 1);

			for (j = 0; j < mp->totloop; j++, ml++) {
				/* add edge user */
				eidx = ml_prev->e;
				if (edge_users[eidx] == INVALID_UNUSED) {
					ed = orig_medge + eidx;
					BLI_assert(ELEM(ml_prev->v,    ed->v1, ed->v2) &&
					           ELEM(ml->v, ed->v1, ed->v2));
					edge_users[eidx] = (ml_prev->v > ml->v) == (ed->v1 < ed->v2) ? i : (i + numFaces);
					edge_order[eidx] = j;
				}
				else {
					edge_users[eidx] = INVALID_PAIR;
				}
				ml_prev = ml;
			}
		}

		for (eidx = 0, ed = orig_medge; eidx < numEdges; eidx++, ed++) {
			if (!ELEM(edge_users[eidx], INVALID_UNUSED, INVALID_PAIR)) {
				BLI_BITMAP_ENABLE(orig_mvert_tag, ed->v1);
				BLI_BITMAP_ENABLE(orig_mvert_tag, ed->v2);
				STACK_PUSH(new_edge_arr, eidx);
				newFaces++;
				newLoops += 4;
			}
		}

		for (i = 0; i < numVerts; i++) {
			if (BLI_BITMAP_TEST(orig_mvert_tag, i)) {
				old_vert_arr[i] = STACK_SIZE(new_vert_arr);
				STACK_PUSH(new_vert_arr, i);
				rimVerts++;
			}
			else {
				old_vert_arr[i] = INVALID_UNUSED;
			}
		}

		MEM_freeN(orig_mvert_tag);
	}

	if (do_shell == false) {
		/* only add rim vertices */
		newVerts = rimVerts;
		/* each extruded face needs an opposite edge */
		newEdges = newFaces;
	}
	else {
		/* (stride == 2) in this case, so no need to add newVerts/newEdges */
		BLI_assert(newVerts == 0);
		BLI_assert(newEdges == 0);
	}

	if (smd->flag & MOD_SOLIDIFY_NORMAL_CALC) {
		vert_nors = MEM_callocN(sizeof(float) * (size_t)numVerts * 3, "mod_solid_vno_hq");
		dm_calc_normal(dm, face_nors, vert_nors);
	}

	result = CDDM_from_template(dm,
	                            (int)((numVerts * stride) + newVerts),
	                            (int)((numEdges * stride) + newEdges + rimVerts), 0,
	                            (int)((numLoops * stride) + newLoops),
	                            (int)((numFaces * stride) + newFaces));

	mpoly = CDDM_get_polys(result);
	mloop = CDDM_get_loops(result);
	medge = CDDM_get_edges(result);
	mvert = CDDM_get_verts(result);

	if (do_shell) {
		DM_copy_vert_data(dm, result, 0, 0, (int)numVerts);
		DM_copy_vert_data(dm, result, 0, (int)numVerts, (int)numVerts);

		DM_copy_edge_data(dm, result, 0, 0, (int)numEdges);
		DM_copy_edge_data(dm, result, 0, (int)numEdges, (int)numEdges);

		DM_copy_loop_data(dm, result, 0, 0, (int)numLoops);
		DM_copy_loop_data(dm, result, 0, (int)numLoops, (int)numLoops);

		DM_copy_poly_data(dm, result, 0, 0, (int)numFaces);
		DM_copy_poly_data(dm, result, 0, (int)numFaces, (int)numFaces);
	}
	else {
		int i, j;
		DM_copy_vert_data(dm, result, 0, 0, (int)numVerts);
		for (i = 0, j = (int)numVerts; i < numVerts; i++) {
			if (old_vert_arr[i] != INVALID_UNUSED) {
				DM_copy_vert_data(dm, result, i, j, 1);
				j++;
			}
		}

		DM_copy_edge_data(dm, result, 0, 0, (int)numEdges);

		for (i = 0, j = (int)numEdges; i < numEdges; i++) {
			if (!ELEM(edge_users[i], INVALID_UNUSED, INVALID_PAIR)) {
				MEdge *ed_src, *ed_dst;
				DM_copy_edge_data(dm, result, i, j, 1);

				ed_src = &medge[i];
				ed_dst = &medge[j];
				ed_dst->v1 = old_vert_arr[ed_src->v1] + numVerts;
				ed_dst->v2 = old_vert_arr[ed_src->v2] + numVerts;
				j++;
			}
		}

		/* will be created later */
		DM_copy_loop_data(dm, result, 0, 0, (int)numLoops);
		DM_copy_poly_data(dm, result, 0, 0, (int)numFaces);
	}

#undef INVALID_UNUSED
#undef INVALID_PAIR


	/* initializes: (i_end, do_shell_align, mv)  */
#define INIT_VERT_ARRAY_OFFSETS(test) \
	if (((ofs_new >= ofs_orig) == do_flip) == test) { \
		i_end = numVerts; \
		do_shell_align = true; \
		mv = mvert; \
	} \
	else { \
		if (do_shell) { \
			i_end = numVerts; \
			do_shell_align = true; \
		} \
		else { \
			i_end = newVerts ; \
			do_shell_align = false; \
		} \
		mv = &mvert[numVerts]; \
	} (void)0


	/* flip normals */

	if (do_shell) {
		unsigned int i;

		mp = mpoly + numFaces;
		for (i = 0; i < dm->numPolyData; i++, mp++) {
			MLoop *ml2;
			unsigned int e;
			int j;

			ml2 = mloop + mp->loopstart + dm->numLoopData;
			for (j = 0; j < mp->totloop; j++) {
				CustomData_copy_data(&dm->loopData, &result->loopData, mp->loopstart + j,
				                     mp->loopstart + (mp->totloop - j - 1) + dm->numLoopData, 1);
			}

			if (mat_ofs) {
				mp->mat_nr += mat_ofs;
				CLAMP(mp->mat_nr, 0, mat_nr_max);
			}

			e = ml2[0].e;
			for (j = 0; j < mp->totloop - 1; j++) {
				ml2[j].e = ml2[j + 1].e;
			}
			ml2[mp->totloop - 1].e = e;

			mp->loopstart += dm->numLoopData;

			for (j = 0; j < mp->totloop; j++) {
				ml2[j].e += numEdges;
				ml2[j].v += numVerts;
			}
		}

		for (i = 0, ed = medge + numEdges; i < numEdges; i++, ed++) {
			ed->v1 += numVerts;
			ed->v2 += numVerts;
		}
	}

	/* note, copied vertex layers don't have flipped normals yet. do this after applying offset */
	if ((smd->flag & MOD_SOLIDIFY_EVEN) == 0) {
		/* no even thickness, very simple */
		float scalar_short;
		float scalar_short_vgroup;

		/* for clamping */
		float *vert_lens = NULL;
		const float offset    = fabsf(smd->offset) * smd->offset_clamp;
		const float offset_sq = offset * offset;

		if (do_clamp) {
			unsigned int i;

			vert_lens = MEM_mallocN(sizeof(float) * numVerts, "vert_lens");
			copy_vn_fl(vert_lens, (int)numVerts, FLT_MAX);
			for (i = 0; i < numEdges; i++) {
				const float ed_len_sq = len_squared_v3v3(mvert[medge[i].v1].co, mvert[medge[i].v2].co);
				vert_lens[medge[i].v1] = min_ff(vert_lens[medge[i].v1], ed_len_sq);
				vert_lens[medge[i].v2] = min_ff(vert_lens[medge[i].v2], ed_len_sq);
			}
		}

		if (ofs_new != 0.0f) {
			unsigned int i_orig, i_end;
			bool do_shell_align;

			scalar_short = scalar_short_vgroup = ofs_new / 32767.0f;

			INIT_VERT_ARRAY_OFFSETS(false);

			for (i_orig = 0; i_orig < i_end; i_orig++, mv++) {
				const unsigned int i = do_shell_align ? i_orig : new_vert_arr[i_orig];
				if (dvert) {
					MDeformVert *dv = &dvert[i];
					if (defgrp_invert) scalar_short_vgroup = 1.0f - defvert_find_weight(dv, defgrp_index);
					else scalar_short_vgroup = defvert_find_weight(dv, defgrp_index);
					scalar_short_vgroup = (offset_fac_vg + (scalar_short_vgroup * offset_fac_vg_inv)) * scalar_short;
				}
				if (do_clamp) {
					/* always reset becaise we may have set before */
					if (dvert == NULL) {
						scalar_short_vgroup = scalar_short;
					}
					if (vert_lens[i] < offset_sq) {
						float scalar = sqrtf(vert_lens[i]) / offset;
						scalar_short_vgroup *= scalar;
					}
				}
				madd_v3v3short_fl(mv->co, mv->no, scalar_short_vgroup);
			}
		}

		if (ofs_orig != 0.0f) {
			unsigned int i_orig, i_end;
			bool do_shell_align;

			scalar_short = scalar_short_vgroup = ofs_orig / 32767.0f;

			/* as above but swapped */
			INIT_VERT_ARRAY_OFFSETS(true);

			for (i_orig = 0; i_orig < i_end; i_orig++, mv++) {
				const unsigned int i = do_shell_align ? i_orig : new_vert_arr[i_orig];
				if (dvert) {
					MDeformVert *dv = &dvert[i];
					if (defgrp_invert) scalar_short_vgroup = 1.0f - defvert_find_weight(dv, defgrp_index);
					else scalar_short_vgroup = defvert_find_weight(dv, defgrp_index);
					scalar_short_vgroup = (offset_fac_vg + (scalar_short_vgroup * offset_fac_vg_inv)) * scalar_short;
				}
				if (do_clamp) {
					/* always reset becaise we may have set before */
					if (dvert == NULL) {
						scalar_short_vgroup = scalar_short;
					}
					if (vert_lens[i] < offset_sq) {
						float scalar = sqrtf(vert_lens[i]) / offset;
						scalar_short_vgroup *= scalar;
					}
				}
				madd_v3v3short_fl(mv->co, mv->no, scalar_short_vgroup);
			}
		}

		if (do_clamp) {
			MEM_freeN(vert_lens);
		}
	}
	else {
#ifdef USE_NONMANIFOLD_WORKAROUND
		const bool check_non_manifold = (smd->flag & MOD_SOLIDIFY_NORMAL_CALC) != 0;
#endif
		/* same as EM_solidify() in editmesh_lib.c */
		float *vert_angles = MEM_callocN(sizeof(float) * numVerts * 2, "mod_solid_pair"); /* 2 in 1 */
		float *vert_accum = vert_angles + numVerts;
		unsigned int vidx;
		unsigned int i;

		if (vert_nors == NULL) {
			vert_nors = MEM_mallocN(sizeof(float) * numVerts * 3, "mod_solid_vno");
			for (i = 0, mv = mvert; i < numVerts; i++, mv++) {
				normal_short_to_float_v3(vert_nors[i], mv->no);
			}
		}

		for (i = 0, mp = mpoly; i < numFaces; i++, mp++) {
			/* #BKE_mesh_calc_poly_angles logic is inlined here */
			float nor_prev[3];
			float nor_next[3];

			int i_curr = mp->totloop - 1;
			int i_next = 0;

			ml = &mloop[mp->loopstart];

			sub_v3_v3v3(nor_prev, mvert[ml[i_curr - 1].v].co, mvert[ml[i_curr].v].co);
			normalize_v3(nor_prev);

			while (i_next < mp->totloop) {
				float angle;
				sub_v3_v3v3(nor_next, mvert[ml[i_curr].v].co, mvert[ml[i_next].v].co);
				normalize_v3(nor_next);
				angle = angle_normalized_v3v3(nor_prev, nor_next);


				/* --- not related to angle calc --- */
				if (angle < FLT_EPSILON) {
					angle = FLT_EPSILON;
				}

				vidx = ml[i_curr].v;
				vert_accum[vidx] += angle;

#ifdef USE_NONMANIFOLD_WORKAROUND
				/* skip 3+ face user edges */
				if ((check_non_manifold == false) ||
				    LIKELY(((orig_medge[ml[i_curr].e].flag & ME_EDGE_TMP_TAG) == 0) &&
				           ((orig_medge[ml[i_next].e].flag & ME_EDGE_TMP_TAG) == 0)))
				{
					vert_angles[vidx] += shell_v3v3_normalized_to_dist(vert_nors[vidx], face_nors[i]) * angle;
				}
				else {
					vert_angles[vidx] += angle;
				}
#else
				vert_angles[vidx] += shell_v3v3_normalized_to_dist(vert_nors[vidx], face_nors[i]) * angle;
#endif
				/* --- end non-angle-calc section --- */


				/* step */
				copy_v3_v3(nor_prev, nor_next);
				i_curr = i_next;
				i_next++;
			}
		}

		/* vertex group support */
		if (dvert) {
			MDeformVert *dv = dvert;
			float scalar;

			if (defgrp_invert) {
				for (i = 0; i < numVerts; i++, dv++) {
					scalar = 1.0f - defvert_find_weight(dv, defgrp_index);
					scalar = offset_fac_vg + (scalar * offset_fac_vg_inv);
					vert_angles[i] *= scalar;
				}
			}
			else {
				for (i = 0; i < numVerts; i++, dv++) {
					scalar = defvert_find_weight(dv, defgrp_index);
					scalar = offset_fac_vg + (scalar * offset_fac_vg_inv);
					vert_angles[i] *= scalar;
				}
			}
		}

		if (do_clamp) {
			float *vert_lens_sq = MEM_mallocN(sizeof(float) * numVerts, "vert_lens");
			const float offset    = fabsf(smd->offset) * smd->offset_clamp;
			const float offset_sq = offset * offset;
			copy_vn_fl(vert_lens_sq, (int)numVerts, FLT_MAX);
			for (i = 0; i < numEdges; i++) {
				const float ed_len = len_squared_v3v3(mvert[medge[i].v1].co, mvert[medge[i].v2].co);
				vert_lens_sq[medge[i].v1] = min_ff(vert_lens_sq[medge[i].v1], ed_len);
				vert_lens_sq[medge[i].v2] = min_ff(vert_lens_sq[medge[i].v2], ed_len);
			}
			for (i = 0; i < numVerts; i++) {
				if (vert_lens_sq[i] < offset_sq) {
					float scalar = sqrtf(vert_lens_sq[i]) / offset;
					vert_angles[i] *= scalar;
				}
			}
			MEM_freeN(vert_lens_sq);
		}

		if (ofs_new != 0.0f) {
			unsigned int i_orig, i_end;
			bool do_shell_align;

			INIT_VERT_ARRAY_OFFSETS(false);

			for (i_orig = 0; i_orig < i_end; i_orig++, mv++) {
				const unsigned int i = do_shell_align ? i_orig : new_vert_arr[i_orig];
				if (vert_accum[i]) { /* zero if unselected */
					madd_v3_v3fl(mv->co, vert_nors[i], ofs_new * (vert_angles[i] / vert_accum[i]));
				}
			}
		}

		if (ofs_orig != 0.0f) {
			unsigned int i_orig, i_end;
			bool do_shell_align;

			/* same as above but swapped, intentional use of 'ofs_new' */
			INIT_VERT_ARRAY_OFFSETS(true);

			for (i_orig = 0; i_orig < i_end; i_orig++, mv++) {
				const unsigned int i = do_shell_align ? i_orig : new_vert_arr[i_orig];
				if (vert_accum[i]) { /* zero if unselected */
					madd_v3_v3fl(mv->co, vert_nors[i], ofs_orig * (vert_angles[i] / vert_accum[i]));
				}
			}
		}

		MEM_freeN(vert_angles);
	}

	if (vert_nors)
		MEM_freeN(vert_nors);

	/* must recalculate normals with vgroups since they can displace unevenly [#26888] */
	if ((dm->dirty & DM_DIRTY_NORMALS) || (smd->flag & MOD_SOLIDIFY_RIM) || dvert) {
		result->dirty |= DM_DIRTY_NORMALS;
	}
	else if (do_shell) {
		unsigned int i;
		/* flip vertex normals for copied verts */
		mv = mvert + numVerts;
		for (i = 0; i < numVerts; i++, mv++) {
			negate_v3_short(mv->no);
		}
	}

	if (smd->flag & MOD_SOLIDIFY_RIM) {
		unsigned int i;

		/* bugger, need to re-calculate the normals for the new edge faces.
		 * This could be done in many ways, but probably the quickest way
		 * is to calculate the average normals for side faces only.
		 * Then blend them with the normals of the edge verts.
		 *
		 * at the moment its easiest to allocate an entire array for every vertex,
		 * even though we only need edge verts - campbell
		 */

#define SOLIDIFY_SIDE_NORMALS

#ifdef SOLIDIFY_SIDE_NORMALS
		const bool do_side_normals = !(result->dirty & DM_DIRTY_NORMALS);
		/* annoying to allocate these since we only need the edge verts, */
		float (*edge_vert_nos)[3] = do_side_normals ? MEM_callocN(sizeof(float) * numVerts * 3, __func__) : NULL;
		float nor[3];
#endif
		const unsigned char crease_rim = smd->crease_rim * 255.0f;
		const unsigned char crease_outer = smd->crease_outer * 255.0f;
		const unsigned char crease_inner = smd->crease_inner * 255.0f;

		int *origindex_edge;
		int *orig_ed;
		unsigned int j;

		if (crease_rim || crease_outer || crease_inner) {
			result->cd_flag |= ME_CDFLAG_EDGE_CREASE;
		}

		/* add faces & edges */
		origindex_edge = result->getEdgeDataArray(result, CD_ORIGINDEX);
		ed = &medge[(numEdges * stride) + newEdges];  /* start after copied edges */
		orig_ed = &origindex_edge[(numEdges * stride) + newEdges];
		for (i = 0; i < rimVerts; i++, ed++, orig_ed++) {
			ed->v1 = new_vert_arr[i];
			ed->v2 = (do_shell ? new_vert_arr[i] : i) + numVerts;
			ed->flag |= ME_EDGEDRAW;

			*orig_ed = ORIGINDEX_NONE;

			if (crease_rim) {
				ed->crease = crease_rim;
			}
		}

		/* faces */
		mp = mpoly + (numFaces * stride);
		ml = mloop + (numLoops * stride);
		j = 0;
		for (i = 0; i < newFaces; i++, mp++) {
			unsigned int eidx = new_edge_arr[i];
			unsigned int fidx = edge_users[eidx];
			int k1, k2;
			bool flip;

			if (fidx >= numFaces) {
				fidx -= numFaces;
				flip = true;
			}
			else {
				flip = false;
			}

			ed = medge + eidx;

			/* copy most of the face settings */
			DM_copy_poly_data(dm, result, (int)fidx, (int)((numFaces * stride) + i), 1);
			mp->loopstart = (int)(j + (numLoops * stride));
			mp->flag = mpoly[fidx].flag;

			/* notice we use 'mp->totloop' which is later overwritten,
			 * we could lookup the original face but theres no point since this is a copy
			 * and will have the same value, just take care when changing order of assignment */
			k1 = mpoly[fidx].loopstart + (((edge_order[eidx] - 1) + mp->totloop) % mp->totloop);  /* prev loop */
			k2 = mpoly[fidx].loopstart +   (edge_order[eidx]);

			mp->totloop = 4;

			CustomData_copy_data(&dm->loopData, &result->loopData, k2, (int)((numLoops * stride) + j + 0), 1);
			CustomData_copy_data(&dm->loopData, &result->loopData, k1, (int)((numLoops * stride) + j + 1), 1);
			CustomData_copy_data(&dm->loopData, &result->loopData, k1, (int)((numLoops * stride) + j + 2), 1);
			CustomData_copy_data(&dm->loopData, &result->loopData, k2, (int)((numLoops * stride) + j + 3), 1);

			if (flip == false) {
				ml[j].v = ed->v1;
				ml[j++].e = eidx;

				ml[j].v = ed->v2;
				ml[j++].e = (numEdges * stride) + old_vert_arr[ed->v2] + newEdges;

				ml[j].v = (do_shell ? ed->v2 : old_vert_arr[ed->v2]) + numVerts;
				ml[j++].e = (do_shell ? eidx : i) + numEdges;

				ml[j].v = (do_shell ? ed->v1 : old_vert_arr[ed->v1]) + numVerts;
				ml[j++].e = (numEdges * stride) + old_vert_arr[ed->v1] + newEdges;
			}
			else {
				ml[j].v = ed->v2;
				ml[j++].e = eidx;

				ml[j].v = ed->v1;
				ml[j++].e = (numEdges * stride) + old_vert_arr[ed->v1] + newEdges;

				ml[j].v = (do_shell ? ed->v1 : old_vert_arr[ed->v1]) + numVerts;
				ml[j++].e = (do_shell ? eidx : i) + numEdges;

				ml[j].v = (do_shell ? ed->v2 : old_vert_arr[ed->v2]) + numVerts;
				ml[j++].e = (numEdges * stride) + old_vert_arr[ed->v2] + newEdges;
			}

			origindex_edge[ml[j - 3].e] = ORIGINDEX_NONE;
			origindex_edge[ml[j - 1].e] = ORIGINDEX_NONE;

			/* use the next material index if option enabled */
			if (mat_ofs_rim) {
				mp->mat_nr += mat_ofs_rim;
				CLAMP(mp->mat_nr, 0, mat_nr_max);
			}
			if (crease_outer) {
				/* crease += crease_outer; without wrapping */
				char *cr = &(ed->crease);
				int tcr = *cr + crease_outer;
				*cr = tcr > 255 ? 255 : tcr;
			}

			if (crease_inner) {
				/* crease += crease_inner; without wrapping */
				char *cr = &(medge[numEdges + (do_shell ? eidx : i)].crease);
				int tcr = *cr + crease_inner;
				*cr = tcr > 255 ? 255 : tcr;
			}

#ifdef SOLIDIFY_SIDE_NORMALS
			if (do_side_normals) {
				normal_quad_v3(nor,
				               mvert[ml[j - 4].v].co,
				               mvert[ml[j - 3].v].co,
				               mvert[ml[j - 2].v].co,
				               mvert[ml[j - 1].v].co);

				add_v3_v3(edge_vert_nos[ed->v1], nor);
				add_v3_v3(edge_vert_nos[ed->v2], nor);
			}
#endif
		}

#ifdef SOLIDIFY_SIDE_NORMALS
		if (do_side_normals) {
			ed = medge + (numEdges * stride);
			for (i = 0; i < rimVerts; i++, ed++) {
				float nor_cpy[3];
				short *nor_short;
				int k;

				/* note, only the first vertex (lower half of the index) is calculated */
				normalize_v3_v3(nor_cpy, edge_vert_nos[ed->v1]);

				for (k = 0; k < 2; k++) { /* loop over both verts of the edge */
					nor_short = mvert[*(&ed->v1 + k)].no;
					normal_short_to_float_v3(nor, nor_short);
					add_v3_v3(nor, nor_cpy);
					normalize_v3(nor);
					normal_float_to_short_v3(nor_short, nor);
				}
			}

			MEM_freeN(edge_vert_nos);
		}
#endif

		MEM_freeN(new_vert_arr);
		MEM_freeN(new_edge_arr);

		MEM_freeN(edge_users);
		MEM_freeN(edge_order);
	}

	if (old_vert_arr)
		MEM_freeN(old_vert_arr);

	if (face_nors)
		MEM_freeN(face_nors);

	if (numFaces == 0 && numEdges != 0) {
		modifier_setError(md, "Faces needed for useful output");
	}

	return result;
}

#undef SOLIDIFY_SIDE_NORMALS

static bool dependsOnNormals(ModifierData *UNUSED(md))
{
	/* even when we calculate our own normals,
	 * the vertex normals are used as a fallback */
	return true;
}

ModifierTypeInfo modifierType_Solidify = {
	/* name */              "Solidify",
	/* structName */        "SolidifyModifierData",
	/* structSize */        sizeof(SolidifyModifierData),
	/* type */              eModifierTypeType_Constructive,

	/* flags */             eModifierTypeFlag_AcceptsMesh |
	                        eModifierTypeFlag_AcceptsCVs |
	                        eModifierTypeFlag_SupportsMapping |
	                        eModifierTypeFlag_SupportsEditmode |
	                        eModifierTypeFlag_EnableInEditmode,

	/* copyData */          copyData,
	/* deformVerts */       NULL,
	/* deformMatrices */    NULL,
	/* deformVertsEM */     NULL,
	/* deformMatricesEM */  NULL,
	/* applyModifier */     applyModifier,
	/* applyModifierEM */   NULL,
	/* initData */          initData,
	/* requiredDataMask */  requiredDataMask,
	/* freeData */          NULL,
	/* isDisabled */        NULL,
	/* updateDepgraph */    NULL,
	/* updateDepsgraph */   NULL,
	/* dependsOnTime */     NULL,
	/* dependsOnNormals */  dependsOnNormals,
	/* foreachObjectLink */ NULL,
	/* foreachIDLink */     NULL,
	/* foreachTexLink */    NULL,
};