griefith/test
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Cleanup: comments in convexhull_2d, correct variable name

Browse Source 
Also remove BLI_ prefix from static function.
This commit is contained in:
Campbell Barton
2024-02-12 20:17:20 +11:00
parent b91918564d
commit f4f97ea979
2 changed files with 44 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
source/blender/blenlib/BLI_convexhull_2d.h
View File

@@ -17,10 +17,12 @@ extern "C" {
*
* \param points: An array of 2D points.
* \param points_num: The number of points in points.
* \param r_points: An array of the convex hull vertex indices (max is n).
* \param r_points: An array of the convex hull vertex indices (max is `points_num`).
* Vertices are ordered counter clockwise, the polygons cross product is always negative (or zero).
*
* \return The number of indices in r_points.
*
* \note Performance is `O(n.log(n))`, same as `qsort`.
* \note Performance is `O(points_num.log(points_num))`, same as `qsort`.
*/
int BLI_convexhull_2d(const float (*points)[2], int points_num, int r_points[/*points_num*/]);
@@ -36,7 +38,7 @@ float BLI_convexhull_aabb_fit_hull_2d(const float (*points_hull)[2], int points_
*
* \note We could return the index of the best edge too if its needed.
*
* \param points: Arbitrary 2d points.
* \param points: Arbitrary 2D points.
*/
float BLI_convexhull_aabb_fit_points_2d(const float (*points)[2], int points_num);

74
source/blender/blenlib/intern/convexhull_2d.cc
View File

@@ -42,18 +42,21 @@ 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]);
}
static int BLI_convexhull_2d_sorted(const float (*points)[2], const int points_num, int r_points[])
static int convexhull_2d_sorted(const float (*points)[2], const int points_num, int r_points[])
{
BLI_assert(points_num >= 2); /* Doesn't handle trivial cases. */
/* the output array r_points[] will be used as the stack */
/* 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 */
/* Indices for bottom and top of the stack. */
int top = -1;
/* Array scan index. */
int i;
int minmin, minmax;
int maxmin, maxmax;
float xmax;
/* Get the indices of points with min x-coord and min|max y-coord */
/* Get the indices of points with min X-coord and min|max Y-coord. */
float xmin = points[0][0];
for (i = 1; i < points_num; i++) {
if (points[i][0] != xmin) {
@@ -63,18 +66,18 @@ static int BLI_convexhull_2d_sorted(const float (*points)[2], const int points_n
minmin = 0;
minmax = i - 1;
if (minmax == points_num - 1) { /* degenerate case: all x-coords == xmin */
if (minmax == points_num - 1) { /* Degenerate case: all x-coords == X-min. */
r_points[++top] = minmin;
if (points[minmax][1] != points[minmin][1]) {
/* a nontrivial segment */
/* A nontrivial segment. */
r_points[++top] = minmax;
}
r_points[++top] = minmin; /* add polygon endpoint */
r_points[++top] = minmin; /* Add polygon endpoint. */
BLI_assert(top + 1 <= points_num);
return top + 1;
}
/* Get the indices of points with max x-coord and min|max y-coord */
/* Get the indices of points with max X-coord and min|max Y-coord. */
maxmax = points_num - 1;
xmax = points[points_num - 1][0];
@@ -85,57 +88,57 @@ static int BLI_convexhull_2d_sorted(const float (*points)[2], const int points_n
}
maxmin = i + 1;
/* Compute the lower hull on the stack r_points */
r_points[++top] = minmin; /* push minmin point onto stack */
/* 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] */
/* 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 */
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 */
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 */
break; /* `points[i]` is a new hull vertex. */
}
top--; /* pop top point off stack */
top--; /* Pop top point off stack. */
}
r_points[++top] = i; /* push points[i] onto 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 */
/* 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] */
/* 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 */
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 */
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 */
break; /* points[i] is a new hull vertex. */
}
top--; /* pop top point off stack */
top--; /* Pop top point off stack. */
}
if (points[i][0] == points[r_points[0]][0] && points[i][1] == points[r_points[0]][1]) {
BLI_assert(top + 1 <= points_num);
return top + 1; /* special case (mgomes) */
return top + 1; /* Special case (mgomes). */
}
r_points[++top] = i; /* push points[i] onto stack */
r_points[++top] = i; /* Push points[i] onto stack. */
}
if (minmax != minmin && r_points[0] != minmin) {
r_points[++top] = minmin; /* push joining endpoint onto stack */
r_points[++top] = minmin; /* Push joining endpoint onto stack. */
}
BLI_assert(top + 1 <= points_num);
@@ -143,7 +146,8 @@ static int BLI_convexhull_2d_sorted(const float (*points)[2], const int points_n
}
struct PointRef {
const float *pt; /* 2d vector */
/** 2D vector. */
const float *pt;
};
static int pointref_cmp_yx(const void *a_, const void *b_)
@@ -192,7 +196,7 @@ int BLI_convexhull_2d(const float (*points)[2], const int points_num, int r_poin
memcpy(points_sort[i], points_ref[i].pt, sizeof(float[2]));
}
int points_hull_num = BLI_convexhull_2d_sorted(points_sort, points_num, r_points);
int points_hull_num = convexhull_2d_sorted(points_sort, points_num, r_points);
/* Map back to the unsorted index values. */
for (int i = 0; i < points_hull_num; i++) {
@@ -214,12 +218,12 @@ int BLI_convexhull_2d(const float (*points)[2], const int points_num, int r_poin
/** \name Utility Convex-Hull Functions
* \{ */
float BLI_convexhull_aabb_fit_hull_2d(const float (*points_hull)[2], int points_num)
float BLI_convexhull_aabb_fit_hull_2d(const float (*points_hull)[2], int points_hull_num)
{
float area_best = FLT_MAX;
float dvec_best[2]; /* best angle, delay atan2 */
for (int i = 0, i_prev = points_num - 1; i < points_num; i_prev = i++) {
for (int i = 0, i_prev = points_hull_num - 1; i < points_hull_num; i_prev = i++) {
const float *ev_a = points_hull[i];
const float *ev_b = points_hull[i_prev];
float dvec[2]; /* 2d rotation matrix */
@@ -232,7 +236,7 @@ float BLI_convexhull_aabb_fit_hull_2d(const float (*points_hull)[2], int points_
float min[2] = {FLT_MAX, FLT_MAX}, max[2] = {-FLT_MAX, -FLT_MAX};
float area_test;
for (int j = 0; j < points_num; j++) {
for (int j = 0; j < points_hull_num; j++) {
float tvec[2];
mul_v2_v2_cw(tvec, dvec, points_hull[j]);