Commit: 44522a5b98f908928e93ab32c9d6046de4342d9b
Author: Campbell Barton
Date: Wed Oct 26 20:26:32 2016 +1100
Branches: master
https://developer.blender.org/rB44522a5b98f908928e93ab32c9d6046de4342d9b
BLI_bitmap_draw_2d: optimize polygon filling
Existing method was fine for basic polygons but didn't scale well
because its was checking all coordinates for every y-pixel.
Heres an optimized version.
Basic logic remains the same this just maintains an ordered list of
intersections,
tracking in-out points, to avoid re-computing every row,
this means sorting is only done once when out of order segments are found,
the segments only need to be re-ordered if they cross each other.
Speedup isn't linear, test with full-screen complex lasso gave 11x speedup.
===================================================================
M source/blender/blenlib/intern/bitmap_draw_2d.c
===================================================================
diff --git a/source/blender/blenlib/intern/bitmap_draw_2d.c
b/source/blender/blenlib/intern/bitmap_draw_2d.c
index 11072f6..afc5451 100644
--- a/source/blender/blenlib/intern/bitmap_draw_2d.c
+++ b/source/blender/blenlib/intern/bitmap_draw_2d.c
@@ -29,14 +29,21 @@
* Utility functions for primitive drawing operations.
*/
+#include <limits.h>
+
#include "MEM_guardedalloc.h"
#include "BLI_bitmap_draw_2d.h"
+#include "BLI_math_base.h"
+#include "BLI_sort.h"
#include "BLI_utildefines.h"
#include "BLI_strict_flags.h"
+/* -------------------------------------------------------------------- */
+/* Draw Line */
+
/**
* Plot a line from \a p1 to \a p2 (inclusive).
*/
@@ -107,7 +114,51 @@ void BLI_bitmap_draw_2d_line_v2v2i(
}
}
+
+/* -------------------------------------------------------------------- */
+/* Draw Filled Polygon */
+
+/* sort edge-segments on y, then x axis */
+static int draw_poly_v2i_n__span_y_sort(const void *a_p, const void *b_p, void
*verts_p)
+{
+ const int (*verts)[2] = verts_p;
+ const int *a = a_p;
+ const int *b = b_p;
+ const int *co_a = verts[a[0]];
+ const int *co_b = verts[b[0]];
+
+ if (co_a[1] < co_b[1]) {
+ return -1;
+ }
+ else if (co_a[1] > co_b[1]) {
+ return 1;
+ }
+ else if (co_a[0] < co_b[0]) {
+ return -1;
+ }
+ else if (co_a[0] > co_b[0]) {
+ return 1;
+ }
+ else {
+ /* co_a & co_b are identical, use the line closest to the x-min
*/
+ const int *co = co_a;
+ co_a = verts[a[1]];
+ co_b = verts[b[1]];
+ int ord = (((co_b[0] - co[0]) * (co_a[1] - co[1])) -
+ ((co_a[0] - co[0]) * (co_b[1] - co[1])));
+ if (ord > 0) {
+ return -1;
+ }
+ if (ord < 0) {
+ return 1;
+ }
+ }
+ return 0;
+}
+
/**
+ * Draws a filled polyon with support for self intersections.
+ *
* \param callback: Takes the x, y coords and x-span (\a x_end is not
inclusive),
* note that \a x_end will always be greater than \a x, so we can use:
*
@@ -123,59 +174,158 @@ void BLI_bitmap_draw_2d_poly_v2i_n(
void (*callback)(int x, int x_end, int y, void *), void *userData)
{
/* Originally by Darel Rex Finley, 2007.
- */
+ * Optimized by Campbell Barton, 2016 to track sorted intersections. */
- int nodes, pixel_y, i, j, swap;
- int *node_x = MEM_mallocN(sizeof(*node_x) * (size_t)(nr + 1), __func__);
+ int (*span_y)[2] = MEM_mallocN(sizeof(*span_y) * (size_t)nr, __func__);
+ int span_y_len = 0;
- /* Loop through the rows of the image. */
- for (pixel_y = ymin; pixel_y < ymax; pixel_y++) {
+ for (int i_curr = 0, i_prev = nr - 1; i_curr < nr; i_prev = i_curr++) {
+ const int *co_prev = verts[i_prev];
+ const int *co_curr = verts[i_curr];
- /* Build a list of nodes. */
- nodes = 0; j = nr - 1;
- for (i = 0; i < nr; i++) {
- if ((verts[i][1] < pixel_y && verts[j][1] >= pixel_y) ||
- (verts[j][1] < pixel_y && verts[i][1] >= pixel_y))
+ if (co_prev[1] != co_curr[1]) {
+ /* Any segments entirely above or below the area of
interest can be skipped. */
+ if ((min_ii(co_prev[1], co_curr[1]) >= ymax) ||
+ (max_ii(co_prev[1], co_curr[1]) < ymin))
{
- node_x[nodes++] = (int)(verts[i][0] +
- ((double)(pixel_y -
verts[i][1]) / (verts[j][1] - verts[i][1])) *
- (verts[j][0] -
verts[i][0]));
+ continue;
}
- j = i;
- }
- /* Sort the nodes, via a simple "Bubble" sort. */
- i = 0;
- while (i < nodes - 1) {
- if (node_x[i] > node_x[i + 1]) {
- SWAP_TVAL(swap, node_x[i], node_x[i + 1]);
- if (i) i--;
+ int *s = span_y[span_y_len++];
+ if (co_prev[1] < co_curr[1]) {
+ s[0] = i_prev;
+ s[1] = i_curr;
}
else {
- i++;
+ s[0] = i_curr;
+ s[1] = i_prev;
+ }
+ }
+ }
+
+ BLI_qsort_r(span_y, (size_t)span_y_len, sizeof(*span_y),
draw_poly_v2i_n__span_y_sort, (void *)verts);
+
+ struct NodeX {
+ int span_y_index;
+ int x;
+ } *node_x = MEM_mallocN(sizeof(*node_x) * (size_t)(nr + 1), __func__);
+ int node_x_len = 0;
+
+ int span_y_index = 0;
+ if (span_y_len != 0 && verts[span_y[0][0]][1] < ymin) {
+ while ((span_y_index < span_y_len) &&
+ (verts[span_y[span_y_index][0]][1] < ymin))
+ {
+ BLI_assert(verts[span_y[span_y_index][0]][1] <
+ verts[span_y[span_y_index][1]][1]);
+ if (verts[span_y[span_y_index][1]][1] >= ymin) {
+ struct NodeX *n = &node_x[node_x_len++];
+ n->span_y_index = span_y_index;
+ }
+ span_y_index += 1;
+ }
+ }
+
+ /* Loop through the rows of the image. */
+ for (int pixel_y = ymin; pixel_y < ymax; pixel_y++) {
+ bool is_sorted = true;
+ bool do_remove = false;
+
+ for (int i = 0, x_ix_prev = INT_MIN; i < node_x_len; i++) {
+ struct NodeX *n = &node_x[i];
+ const int *s = span_y[n->span_y_index];
+ const int *co_prev = verts[s[0]];
+ const int *co_curr = verts[s[1]];
+
+ BLI_assert(co_prev[1] < pixel_y && co_curr[1] >=
pixel_y);
+
+ const double x = (co_prev[0] - co_curr[0]);
+ const double y = (co_prev[1] - co_curr[1]);
+ const double y_px = (pixel_y - co_curr[1]);
+ const int x_ix = (int)((double)co_curr[0] + ((y_px /
y) * x));
+ n->x = x_ix;
+
+ if (is_sorted && (x_ix_prev > x_ix)) {
+ is_sorted = false;
+ }
+ if (do_remove == false && co_curr[1] == pixel_y) {
+ do_remove = true;
+ }
+ x_ix_prev = x_ix;
+ }
+
+ /* Sort the nodes, via a simple "Bubble" sort. */
+ if (is_sorted == false) {
+ int i = 0;
+ const int node_x_end = node_x_len - 1;
+ while (i < node_x_end) {
+ if (node_x[i].x > node_x[i + 1].x) {
+ SWAP(struct NodeX, node_x[i], node_x[i
+ 1]);
+ if (i != 0) {
+ i -= 1;
+ }
+ }
+ else {
+ i += 1;
+ }
}
}
/* Fill the pixels between node pairs. */
- for (i = 0; i < nodes; i += 2) {
- if (node_x[i] >= xmax) break;
- if (node_x[i + 1] > xmin) {
- if (node_x[i ] < xmin) node_x[i ] = xmin;
- if (node_x[i + 1] > xmax) node_x[i + 1] = xmax;
-
-#if 0
- /* for many x/y calls */
- for (j = node_x[i]; j < node_x[i + 1]; j++) {
- callback(j - xmin, pixel_y - ymin,
userData);
+ for (int i = 0; i < node_x_len; i += 2) {
+ int x_src = node_x[i].x;
+ int x_dst = node_x[i + 1].x;
+
+ if (x_src >= xmax) {
+ break;
+ }
+
+ if (x_dst > xmin) {
+ if (x_src < xmin) {
+ x_src = xmin;
+ }
+ if (x_dst > xmax) {
+ x_dst = xmax;
}
-#else
/* for single call per x-span */
- if (node_x[i] < node_x[i + 1]) {
- callback(node_x[i] - xmin, node_x[i +
1] - xmin, pixel_y - ymin, userData);
+ if (x_src < x_dst) {
+ callback(x_src - xmin, x_dst - xmin,
pixel_y - ymin, userData);
}
-#endif
}
}
+
+ /* Clear finalized nodes in one pass, only when needed
+ * (avoids excessive array-resizing). */
+ if (do_remove == true) {
+ int i_dst = 0;
+ for (int i_src = 0; i_src < node_x_len; i_src += 1) {
+ const int *s =
span_y[node_x[i_src].span_y_index];
+ const int *co = verts[s[1]];
+ if (co[1] != pixel_y) {
+ if (i_dst != i_src) {
+ /* x is initialized for the
next pixel_y (no need to adjust here) */
+ node_x[i_dst].span_y_index =
node_x[i_src].span_y_index;
+ }
+ i_dst += 1;
+ }
+ }
+ node_x_len = i_dst;
+ }
+
+ /* Scan for new x-nodes */
+ while ((span_y_index < span_y_len) &&
+ (verts[span_y[span_y_index][0]][1] == pixel_y))
+ {
+ /* note, node_x these are just added at the end,
+ * not ideal but sorting once will resolve. */
+
+ /* x is initialized for the next pixel_y */
+ struct NodeX *n = &node_x[node_x_len++];
+ n->span_y_index = span_y_index;
+ span_y_index += 1;
+ }
}
+
+ MEM_freeN(span_y);
MEM_freeN(node_x);
}
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