From deacb3d6b816afe9f86f51b00043821829fb550e Mon Sep 17 00:00:00 2001 From: Campbell Barton Date: Sun, 18 Feb 2018 21:27:33 +1100 Subject: Cleanup: add 2d suffix to BLI files Some of these API's can have 3D versions, explicitly name them 2D. --- source/blender/blenlib/intern/convexhull_2d.c | 331 ++++++++++++++++++++++++++ 1 file changed, 331 insertions(+) create mode 100644 source/blender/blenlib/intern/convexhull_2d.c (limited to 'source/blender/blenlib/intern/convexhull_2d.c') diff --git a/source/blender/blenlib/intern/convexhull_2d.c b/source/blender/blenlib/intern/convexhull_2d.c new file mode 100644 index 00000000000..38928dbbaa0 --- /dev/null +++ b/source/blender/blenlib/intern/convexhull_2d.c @@ -0,0 +1,331 @@ +/* + * ***** 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. + * + * ***** END GPL LICENSE BLOCK ***** + */ + +/** \file blender/blenlib/intern/convexhull_2d.c + * \ingroup bli + */ + + +#include +#include + +#include "MEM_guardedalloc.h" + +#include "BLI_convexhull_2d.h" +#include "BLI_math.h" +#include "BLI_strict_flags.h" +#include "BLI_utildefines.h" + +/* Copyright 2001, softSurfer (www.softsurfer.com) + * This code may be freely used and modified for any purpose + * providing that this copyright notice is included with it. + * SoftSurfer makes no warranty for this code, and cannot be held + * liable for any real or imagined damage resulting from its use. + * Users of this code must verify correctness for their application. + * http://softsurfer.com/Archive/algorithm_0203/algorithm_0203.htm + */ + +/** \name Main Convex-Hull Calculation + * \{ */ + +/** + * tests if a point is Left|On|Right of an infinite line. + * Input: three points P0, P1, and P2 + * \returns > 0.0 for P2 left of the line through P0 and P1. + * = 0.0 for P2 on the line. + * < 0.0 for P2 right of the line. + */ +static float is_left(const float p0[2], const float p1[2], const float p2[2]) +{ + return (p1[0] - p0[0]) * (p2[1] - p0[1]) - (p2[0] - p0[0]) * (p1[1] - p0[1]); +} + +/** + * A.M. Andrew's monotone chain 2D convex hull algorithm + * + * \param points An array of 2D points presorted by increasing x and y-coords. + * \param n The number of points in points. + * \param r_points An array of the convex hull vertex indices (max is n). + * \returns the number of points in r_points. + */ +int BLI_convexhull_2d_sorted(const float (*points)[2], const int n, int r_points[]) +{ + /* the output array r_points[] will be used as the stack */ + int bot = 0; + int top = -1; /* indices for bottom and top of the stack */ + int i; /* array scan index */ + int minmin, minmax; + int maxmin, maxmax; + float xmax; + + /* Get the indices of points with min x-coord and min|max y-coord */ + float xmin = points[0][0]; + for (i = 1; i < n; i++) { + if (points[i][0] != xmin) { + break; + } + } + + minmin = 0; + minmax = i - 1; + if (minmax == n - 1) { /* degenerate case: all x-coords == xmin */ + r_points[++top] = minmin; + if (points[minmax][1] != points[minmin][1]) /* a nontrivial segment */ + r_points[++top] = minmax; + r_points[++top] = minmin; /* add polygon endpoint */ + return top + 1; + } + + /* Get the indices of points with max x-coord and min|max y-coord */ + + maxmax = n - 1; + xmax = points[n - 1][0]; + for (i = n - 2; i >= 0; i--) { + if (points[i][0] != xmax) { + break; + } + } + maxmin = i + 1; + + /* Compute the lower hull on the stack r_points */ + r_points[++top] = minmin; /* push minmin point onto stack */ + i = minmax; + while (++i <= maxmin) { + /* the lower line joins points[minmin] with points[maxmin] */ + if (is_left(points[minmin], points[maxmin], points[i]) >= 0 && i < maxmin) { + continue; /* ignore points[i] above or on the lower line */ + } + + while (top > 0) { /* there are at least 2 points on the stack */ + /* test if points[i] is left of the line at the stack top */ + if (is_left(points[r_points[top - 1]], points[r_points[top]], points[i]) > 0.0f) { + break; /* points[i] is a new hull vertex */ + } + else { + top--; /* pop top point off stack */ + } + } + + r_points[++top] = i; /* push points[i] onto stack */ + } + + /* Next, compute the upper hull on the stack r_points above the bottom hull */ + if (maxmax != maxmin) { /* if distinct xmax points */ + r_points[++top] = maxmax; /* push maxmax point onto stack */ + } + + bot = top; /* the bottom point of the upper hull stack */ + i = maxmin; + while (--i >= minmax) { + /* the upper line joins points[maxmax] with points[minmax] */ + if (is_left(points[maxmax], points[minmax], points[i]) >= 0 && i > minmax) { + continue; /* ignore points[i] below or on the upper line */ + } + + while (top > bot) { /* at least 2 points on the upper stack */ + /* test if points[i] is left of the line at the stack top */ + if (is_left(points[r_points[top - 1]], points[r_points[top]], points[i]) > 0.0f) { + break; /* points[i] is a new hull vertex */ + } + else { + top--; /* pop top point off stack */ + } + } + + if (points[i][0] == points[r_points[0]][0] && points[i][1] == points[r_points[0]][1]) { + return top + 1; /* special case (mgomes) */ + } + + r_points[++top] = i; /* push points[i] onto stack */ + } + + if (minmax != minmin) { + r_points[++top] = minmin; /* push joining endpoint onto stack */ + } + + return top + 1; +} + +struct PointRef { + const float *pt; /* 2d vector */ +}; + +static int pointref_cmp_yx(const void *a_, const void *b_) +{ + const struct PointRef *a = a_; + const struct PointRef *b = b_; + + if (a->pt[1] > b->pt[1]) return 1; + else if (a->pt[1] < b->pt[1]) return -1; + + if (a->pt[0] > b->pt[0]) return 1; + else if (a->pt[0] < b->pt[0]) return -1; + + else return 0; +} + +/** + * A.M. Andrew's monotone chain 2D convex hull algorithm + * + * \param points An array of 2D points. + * \param n The number of points in points. + * \param r_points An array of the convex hull vertex indices (max is n). + * _must_ be allocated as ``n * 2`` because of how its used internally, + * even though the final result will be no more than \a n in size. + * \returns the number of points in r_points. + */ +int BLI_convexhull_2d(const float (*points)[2], const int n, int r_points[]) +{ + struct PointRef *points_ref = MEM_mallocN(sizeof(*points_ref) * (size_t)n, __func__); + float (*points_sort)[2] = MEM_mallocN(sizeof(*points_sort) * (size_t)n, __func__); + int *points_map; + int tot, i; + + for (i = 0; i < n; i++) { + points_ref[i].pt = points[i]; + } + + /* Sort the points by X, then by Y (required by the algorithm) */ + qsort(points_ref, (size_t)n, sizeof(struct PointRef), pointref_cmp_yx); + + for (i = 0; i < n; i++) { + memcpy(points_sort[i], points_ref[i].pt, sizeof(float[2])); + } + + tot = BLI_convexhull_2d_sorted(points_sort, n, r_points); + + /* map back to the original index values */ + points_map = (int *)points_sort; /* abuse float array for temp storage */ + for (i = 0; i < tot; i++) { + points_map[i] = (int)((const float(*)[2])points_ref[r_points[i]].pt - points); + } + + memcpy(r_points, points_map, (size_t)tot * sizeof(*points_map)); + + MEM_freeN(points_ref); + MEM_freeN(points_sort); + + return tot; +} + +/** \} */ + + +/* -------------------------------------------------------------------- */ +/* Helper functions */ + +/** \name Utility Convex-Hull Functions + * \{ */ + +/** + * \return The best angle for fitting the convex hull to an axis aligned bounding box. + * + * Intended to be used with #BLI_convexhull_2d + * + * \param points_hull Ordered hull points + * (result of #BLI_convexhull_2d mapped to a contiguous array). + * + * \note we could return the index of the best edge too if its needed. + */ +float BLI_convexhull_aabb_fit_hull_2d(const float (*points_hull)[2], unsigned int n) +{ + unsigned int i, i_prev; + float area_best = FLT_MAX; + float dvec_best[2]; /* best angle, delay atan2 */ + + i_prev = n - 1; + for (i = 0; i < n; i++) { + const float *ev_a = points_hull[i]; + const float *ev_b = points_hull[i_prev]; + float dvec[2]; /* 2d rotation matrix */ + + sub_v2_v2v2(dvec, ev_a, ev_b); + if (normalize_v2(dvec) != 0.0f) { + /* rotation matrix */ + float min[2] = {FLT_MAX, FLT_MAX}, max[2] = {-FLT_MAX, -FLT_MAX}; + unsigned int j; + float area; + + for (j = 0; j < n; j++) { + float tvec[2]; + mul_v2_v2_cw(tvec, dvec, points_hull[j]); + + min[0] = min_ff(min[0], tvec[0]); + min[1] = min_ff(min[1], tvec[1]); + + max[0] = max_ff(max[0], tvec[0]); + max[1] = max_ff(max[1], tvec[1]); + + area = (max[0] - min[0]) * (max[1] - min[1]); + if (area > area_best) { + break; + } + } + + if (area < area_best) { + area_best = area; + copy_v2_v2(dvec_best, dvec); + } + } + + i_prev = i; + } + + return (area_best != FLT_MAX) ? atan2f(dvec_best[0], dvec_best[1]) : 0.0f; +} + +/** + * Wrap #BLI_convexhull_aabb_fit_hull_2d and do the convex hull calculation. + * + * \param points arbitrary 2d points. + */ +float BLI_convexhull_aabb_fit_points_2d(const float (*points)[2], unsigned int n) +{ + int *index_map; + int tot; + + float angle; + + index_map = MEM_mallocN(sizeof(*index_map) * n * 2, __func__); + + tot = BLI_convexhull_2d(points, (int)n, index_map); + + if (tot) { + float (*points_hull)[2]; + int j; + + points_hull = MEM_mallocN(sizeof(*points_hull) * (size_t)tot, __func__); + for (j = 0; j < tot; j++) { + copy_v2_v2(points_hull[j], points[index_map[j]]); + } + + angle = BLI_convexhull_aabb_fit_hull_2d(points_hull, (unsigned int)tot); + MEM_freeN(points_hull); + } + else { + angle = 0.0f; + } + + MEM_freeN(index_map); + + return angle; +} + +/** \} */ -- cgit v1.2.3