forked from bartvdbraak/blender
Geometry API: polyfill2d, ear clipping polygon filling functions.
Simple/predictable polygon filling functions (no hole support) originally from libgdx which have some advantages over scanfill. - always creates the same number of triangles (never any missing faces). - gives same results for any affine transformation. - doesn't give so many skinny faces by default. made some changes for Blender. - remove last ears first (less to memmove) - step over the ears while clipping to avoid some verts becoming fans to most of the other.
This commit is contained in:
Campbell Barton
parent
bf55eeb216
commit
b9445106b2
44
source/blender/blenlib/BLI_polyfill2d.h
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44
source/blender/blenlib/BLI_polyfill2d.h
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@ -0,0 +1,44 @@
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/*
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* ***** BEGIN GPL LICENSE BLOCK *****
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* ***** END GPL LICENSE BLOCK *****
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*/
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#ifndef __BLI_POLYFILL2D_H__
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#define __BLI_POLYFILL2D_H__
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void BLI_polyfill_calc_ex(
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const float (*coords)[2],
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const unsigned int count,
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unsigned int (*r_tris)[3],
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/* avoid allocating each time */
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unsigned int *r_indices, signed char *r_coords_sign);
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void BLI_polyfill_calc_arena(
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const float (*coords)[2],
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const unsigned int coords_tot,
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unsigned int (*r_tris)[3],
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struct MemArena *arena);
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void BLI_polyfill_calc(
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const float (*coords)[2],
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const unsigned int coords_tot,
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unsigned int (*r_tris)[3]);
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#endif /* __BLI_POLYFILL2D_H__ */
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@ -82,6 +82,7 @@ set(SRC
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intern/md5.c
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intern/noise.c
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intern/path_util.c
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intern/polyfill2d.c
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intern/quadric.c
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intern/rand.c
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intern/rct.c
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@ -148,6 +149,7 @@ set(SRC
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BLI_mempool.h
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BLI_noise.h
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BLI_path_util.h
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BLI_polyfill2d.h
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BLI_quadric.h
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BLI_rand.h
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BLI_rect.h
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375
source/blender/blenlib/intern/polyfill2d.c
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375
source/blender/blenlib/intern/polyfill2d.c
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@ -0,0 +1,375 @@
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/*
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* ***** BEGIN GPL LICENSE BLOCK *****
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* ***** END GPL LICENSE BLOCK *****
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*/
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/** \file blender/blenlib/intern/polyfill2d.c
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* \ingroup bli
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*
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* A simple implementation of the ear cutting algorithm
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* to triangulate simple polygons without holes.
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*
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* \note
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*
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* Changes made for Blender.
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*
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* - loop the array to clip last verts first (less array resizing)
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*
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* - advance the ear to clip each iteration
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* to avoid fan-filling convex shapes (USE_CLIP_EVEN).
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*
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* \note
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*
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* No globals - keep threadsafe.
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*/
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#include "BLI_utildefines.h"
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#include "BLI_math.h"
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#include "BLI_memarena.h"
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#include "BLI_alloca.h"
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#include "BLI_polyfill2d.h" /* own include */
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#include "BLI_strict_flags.h"
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#define SIGN_EPS 0.000001f
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/* avoid fan-fill topology */
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#define USE_CLIP_EVEN
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typedef signed char eSign;
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enum {
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CONCAVE = -1,
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TANGENTIAL = 0,
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CONVEX = 1,
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};
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typedef struct PolyFill {
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unsigned int *indices; /* vertex aligned */
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const float (*coords)[2];
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unsigned int coords_tot;
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eSign *coords_sign;
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/* A polygon with n vertices has a triangulation of n-2 triangles. */
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unsigned int (*tris)[3];
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unsigned int tris_tot;
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} PolyFill;
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/* based on libgdx 2013-11-28, apache 2.0 licensed */
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static eSign pf_coord_sign_calc(PolyFill *pf, unsigned int index);
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static unsigned int pf_index_prev(const PolyFill *pf, const unsigned int index);
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static unsigned int pf_index_next(const PolyFill *pf, unsigned index);
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#ifdef USE_CLIP_EVEN
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static unsigned int pf_ear_tip_find(PolyFill *pf, const unsigned int index_offset);
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#else
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static unsigned int pf_ear_tip_find(PolyFill *pf);
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#endif
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static bool pf_ear_tip_check(PolyFill *pf, const unsigned int index_ear_tip);
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static void pf_ear_tip_cut(PolyFill *pf, unsigned int index_ear_tip);
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BLI_INLINE eSign signum_i(float a)
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{
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if (UNLIKELY(fabsf(a) < SIGN_EPS))
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return 0;
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else if (a > 0.0f)
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return 1;
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else
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return -1;
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}
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static eSign span_tri_v2_sign(const float v1[2], const float v2[2], const float v3[2])
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{
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return signum_i(area_tri_signed_v2(v3, v2, v1));
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}
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static unsigned int *pf_tri_add(PolyFill *pf)
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{
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return pf->tris[pf->tris_tot++];
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}
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static void pf_coord_remove(PolyFill *pf, const unsigned int index)
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{
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ARRAY_DELETE(pf->indices, index, 1, pf->coords_tot);
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ARRAY_DELETE(pf->coords_sign, index, 1, pf->coords_tot);
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pf->coords_tot -= 1;
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}
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static void pf_triangulate(PolyFill *pf)
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{
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/* localize */
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eSign *coords_sign = pf->coords_sign;
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unsigned int index_ear_tip = 0;
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while (pf->coords_tot > 3) {
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unsigned int i_prev, i_next;
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#ifdef USE_CLIP_EVEN
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index_ear_tip = pf_ear_tip_find(pf, index_ear_tip);
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#else
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index_ear_tip = pf_ear_tip_find(pf);
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#endif
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pf_ear_tip_cut(pf, index_ear_tip);
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/* The type of the two vertices adjacent to the clipped vertex may have changed. */
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i_prev = pf_index_prev(pf, index_ear_tip);
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i_next = (index_ear_tip == pf->coords_tot) ? 0 : index_ear_tip;
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coords_sign[i_prev] = pf_coord_sign_calc(pf, i_prev);
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coords_sign[i_next] = pf_coord_sign_calc(pf, i_next);
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#ifdef USE_CLIP_EVEN
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index_ear_tip = i_prev;
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#endif
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}
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if (pf->coords_tot == 3) {
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unsigned int *tri = pf_tri_add(pf);
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tri[0] = pf->indices[0];
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tri[1] = pf->indices[1];
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tri[2] = pf->indices[2];
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}
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}
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/**
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* \return CONCAVE, TANGENTIAL or CONVEX
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*/
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static eSign pf_coord_sign_calc(PolyFill *pf, unsigned int index)
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{
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/* localize */
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unsigned int *indices = pf->indices;
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const float (*coords)[2] = pf->coords;
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return span_tri_v2_sign(
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coords[indices[pf_index_prev(pf, index)]],
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coords[indices[index]],
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coords[indices[pf_index_next(pf, index)]]);
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}
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#ifdef USE_CLIP_EVEN
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static unsigned int pf_ear_tip_find(PolyFill *pf, const unsigned int index_offset)
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#else
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static unsigned int pf_ear_tip_find(PolyFill *pf)
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#endif
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{
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/* localize */
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const eSign *coords_sign = pf->coords_sign;
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const unsigned int coords_tot = pf->coords_tot;
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unsigned int i;
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i = coords_tot;
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while (i--) {
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#ifdef USE_CLIP_EVEN
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unsigned int j = (i + index_offset) % coords_tot;
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if (pf_ear_tip_check(pf, j)) {
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return j;
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}
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#else
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if (pf_ear_tip_check(pf, i)) {
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return i;
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}
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#endif
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}
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/* Desperate mode: if no vertex is an ear tip, we are dealing with a degenerate polygon (e.g. nearly collinear).
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* Note that the input was not necessarily degenerate, but we could have made it so by clipping some valid ears.
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*
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* Idea taken from Martin Held, "FIST: Fast industrial-strength triangulation of polygons", Algorithmica (1998),
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* http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.115.291
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*
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* Return a convex or tangential vertex if one exists.
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*/
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i = coords_tot;
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while (i--) {
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#ifdef USE_CLIP_EVEN
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unsigned int j = (i + index_offset) % coords_tot;
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if (coords_sign[j] != CONCAVE) {
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return j;
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}
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#else
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if (coords_sign[i] != CONCAVE) {
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return i;
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}
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#endif
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}
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/* If all vertices are concave, just return the last one. */
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return coords_tot - 1;
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}
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static bool pf_ear_tip_check(PolyFill *pf, const unsigned int index_ear_tip)
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{
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/* localize */
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const unsigned int *indices = pf->indices;
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const float (*coords)[2] = pf->coords;
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const eSign *coords_sign = pf->coords_sign;
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unsigned int i_prev, i_curr, i_next;
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const float *v1, *v2, *v3;
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if (UNLIKELY(coords_sign[index_ear_tip] == CONCAVE)) {
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return false;
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}
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i_prev = pf_index_prev(pf, index_ear_tip);
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i_next = pf_index_next(pf, index_ear_tip);
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v1 = coords[indices[i_prev]];
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v2 = coords[indices[index_ear_tip]];
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v3 = coords[indices[i_next]];
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/* Check if any point is inside the triangle formed by previous, current and next vertices.
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* Only consider vertices that are not part of this triangle, or else we'll always find one inside. */
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for (i_curr = pf_index_next(pf, i_next); i_curr != i_prev; i_curr = pf_index_next(pf, i_curr)) {
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/* Concave vertices can obviously be inside the candidate ear, but so can tangential vertices
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* if they coincide with one of the triangle's vertices. */
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if (coords_sign[i_curr] != CONVEX) {
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const float *v = coords[indices[i_curr]];
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/* Because the polygon has clockwise winding order,
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* the area sign will be positive if the point is strictly inside.
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* It will be 0 on the edge, which we want to include as well. */
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if ((span_tri_v2_sign(v1, v2, v) == CONVEX) &&
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(span_tri_v2_sign(v2, v3, v) == CONVEX) &&
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(span_tri_v2_sign(v3, v1, v) == CONVEX))
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{
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return false;
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}
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}
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}
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return true;
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}
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static void pf_ear_tip_cut(PolyFill *pf, unsigned int index_ear_tip)
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{
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unsigned int *tri = pf_tri_add(pf);
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tri[0] = pf->indices[pf_index_prev(pf, index_ear_tip)];
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tri[1] = pf->indices[index_ear_tip];
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tri[2] = pf->indices[pf_index_next(pf, index_ear_tip)];
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pf_coord_remove(pf, index_ear_tip);
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}
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static unsigned int pf_index_prev(const PolyFill *pf, const unsigned int index)
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{
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return (index ? index : pf->coords_tot) - 1;
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}
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static unsigned int pf_index_next(const PolyFill *pf, unsigned index)
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{
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return (index + 1) % pf->coords_tot;
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}
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/**
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* Triangulates the given (convex or concave) simple polygon to a list of triangle vertices.
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* \param vertices pairs describing vertices of the polygon, in either clockwise or counterclockwise order.
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* \return triples of triangle indices in clockwise order.
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* Note the returned array is reused for later calls to the same method.
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*/
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void BLI_polyfill_calc_ex(
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const float (*coords)[2],
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const unsigned int coords_tot,
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unsigned int (*r_tris)[3],
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unsigned int *r_indices, eSign *r_coords_sign)
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{
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PolyFill pf;
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/* localize */
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unsigned int *indices = r_indices;
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eSign *coords_sign = r_coords_sign;
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unsigned int i;
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/* assign all polyfill members here */
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pf.indices = r_indices;
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pf.coords = coords;
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pf.coords_tot = coords_tot;
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pf.coords_sign = r_coords_sign;
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pf.tris = r_tris;
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pf.tris_tot = 0;
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if ((coords_tot < 3) ||
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cross_poly_v2((int)coords_tot, (float(*)[2])coords) > 0.0f)
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{
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for (i = 0; i < coords_tot; i++) {
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indices[i] = i;
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}
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}
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else {
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/* reversed */
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unsigned int n = coords_tot - 1;
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for (i = 0; i < coords_tot; i++) {
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indices[i] = (n - i);
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}
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}
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for (i = 0; i < coords_tot; i++) {
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coords_sign[i] = pf_coord_sign_calc(&pf, i);
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}
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pf_triangulate(&pf);
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}
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void BLI_polyfill_calc_arena(
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const float (*coords)[2],
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const unsigned int coords_tot,
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unsigned int (*r_tris)[3],
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struct MemArena *arena)
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{
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unsigned int *indicies = BLI_memarena_alloc(arena, (int)(sizeof(*indicies) * coords_tot));
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eSign *coords_sign = BLI_memarena_alloc(arena, (int)(sizeof(*coords_sign) * coords_tot));
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BLI_polyfill_calc_ex(
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coords, coords_tot,
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r_tris,
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/* cache */
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indicies, coords_sign);
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/* indicies & coords_sign are no longer needed,
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* caller can clear arena */
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}
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void BLI_polyfill_calc(
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const float (*coords)[2],
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const unsigned int coords_tot,
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unsigned int (*r_tris)[3])
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{
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unsigned int *indicies = BLI_array_alloca(indicies, coords_tot);
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eSign *coords_sign = BLI_array_alloca(coords_sign, coords_tot);
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BLI_polyfill_calc_ex(
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coords, coords_tot,
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r_tris,
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/* cache */
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indicies, coords_sign);
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}
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