blender
/
blender
129
398
Fork 572
Code Issues 6.2k Pull Requests 751 Projects 19 Wiki Activity

BLI_bitmap: 2D triangle drawing function 

Matching polygon filling but no need for allocation or qsort.
This commit is contained in:
Campbell Barton 2018-04-21 18:34:34 +02:00
parent 83cb387944
commit 1e9fb355bf
Notes: blender-bot 2023-02-14 05:59:34 +01:00 
Referenced by issue #54709, Mesh Icon Support
2 changed files with 186 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
source/blender/blenlib/BLI_bitmap_draw_2d.h
View File

@ -29,6 +29,10 @@ void BLI_bitmap_draw_2d_line_v2v2i(
const int p1[2], const int p2[2],
bool (*callback)(int, int, void *), void *userData);
void BLI_bitmap_draw_2d_tri_v2i(
const int p1[2], const int p2[2], const int p3[2],
void (*callback)(int x, int x_end, int y, void *), void *user_data);
void BLI_bitmap_draw_2d_poly_v2i_n(
const int xmin, const int ymin, const int xmax, const int ymax,
const int polyXY[][2], const int polyCorners,

184
source/blender/blenlib/intern/bitmap_draw_2d.c
View File

@ -42,7 +42,8 @@
#include "BLI_strict_flags.h"
/* -------------------------------------------------------------------- */
/* Draw Line */
/** \name Draw Line
* \{ */
/**
* Plot a line from \a p1 to \a p2 (inclusive).
@ -119,9 +120,186 @@ void BLI_bitmap_draw_2d_line_v2v2i(
}
}
/** \} */
/* -------------------------------------------------------------------- */
/* Draw Filled Polygon */
/** \name Draw Filled Triangle
* \{ */
/**
* Fill a triangle
*
* Standard algorithm,
* See: http://www.sunshine2k.de/coding/java/TriangleRasterization/TriangleRasterization.html
*
* Changes to the basic implementation:
*
* - Reuse slope calculation when drawing the second triangle.
* - Don't calculate the 4th point at all for the triangle split.
* - Order line drawing from left to right (minor detail).
* - 1-pixel offsets are applied so adjacent triangles don't overlap.
*
* This is not clipped, a clipped version can be added if needed.
*/
/* Macros could be moved to a shared location. */
#define ORDERED_SWAP(ty, a, b) \
if (a > b) { SWAP(ty, a, b); } ((void)0)
#define ORDERED_SWAP_BY(ty, a, b, by) \
if ((a by) > (b by)) { SWAP(ty, a, b); } ((void)0)
#define ORDER_VARS2(ty, a, b) \
{ ORDERED_SWAP(ty, a, b); } ((void)0)
#define ORDER_VARS3_BY(ty, a, b, c, by) \
{ \
ORDERED_SWAP_BY(ty, b, c, by); \
ORDERED_SWAP_BY(ty, a, c, by); \
ORDERED_SWAP_BY(ty, a, b, by); \
} ((void)0)
static float inv_slope(const int a[2], const int b[2])
{
return ((float)(a[0] - b[0]) /
(float)(a[1] - b[1]));
}
/**
* <pre>
* *---*
* \ /
* *
* </pre>
*/
static void draw_tri_flat_max(
const int p[2],
const int max_y,
const float inv_slope1,
const float inv_slope2,
void (*callback)(int x, int x_end, int y, void *),
void *user_data)
{
float cur_x1 = (float)p[0];
float cur_x2 = cur_x1;
/* start-end inclusive */
const int min_y = p[1];
const int max_y_end = max_y + 1;
for (int scanline_y = min_y; scanline_y != max_y_end; scanline_y += 1) {
callback((int)cur_x1, 1 + (int)cur_x2, scanline_y, user_data);
cur_x1 += inv_slope1;
cur_x2 += inv_slope2;
}
}
/**
* <pre>
* *
* / \
* *---*
* </pre>
*/
static void draw_tri_flat_min(
const int p[2],
const int min_y,
const float inv_slope1,
const float inv_slope2,
void (*callback)(int x, int x_end, int y, void *),
void *user_data)
{
float cur_x1 = (float)p[0];
float cur_x2 = cur_x1;
/* start-end inclusive */
const int max_y = p[1];
const int min_y_end = min_y - 1;
for (int scanline_y = max_y; scanline_y != min_y_end; scanline_y -= 1) {
callback((int)cur_x1, 1 + (int)cur_x2, scanline_y, user_data);
cur_x1 -= inv_slope1;
cur_x2 -= inv_slope2;
}
}
/**
* \note Unclipped (clipped version can be added if needed).
*/
void BLI_bitmap_draw_2d_tri_v2i(
/* all 2d */
const int p1[2],
const int p2[2],
const int p3[2],
void (*callback)(int x, int x_end, int y, void *),
void *user_data)
{
/* At first sort the three vertices by y-coordinate ascending so p1 is the top-most vertice */
ORDER_VARS3_BY(const int *, p1, p2, p3, [1]);
BLI_assert(p1[1] <= p2[1] && p2[1] <= p3[1]);
/* Check for trivial case of bottom-flat triangle. */
if (p2[1] == p3[1]) {
float inv_slope1 = inv_slope(p2, p1);
float inv_slope2 = inv_slope(p3, p1);
ORDER_VARS2(float, inv_slope1, inv_slope2);
BLI_assert(inv_slope1 <= inv_slope2);
draw_tri_flat_max(
p1, p2[1],
inv_slope1, inv_slope2,
callback, user_data);
}
else if (p1[1] == p2[1]) {
/* Check for trivial case of top-flat triangle. */
float inv_slope1 = inv_slope(p3, p1);
float inv_slope2 = inv_slope(p3, p2);
ORDER_VARS2(float, inv_slope2, inv_slope1);
BLI_assert(inv_slope1 >= inv_slope2);
draw_tri_flat_min(
p3, p2[1] + 1, /* avoid overlap */
inv_slope1, inv_slope2,
callback, user_data);
}
else {
/* General case - split the triangle in a top-flat and bottom-flat one. */
const float inv_slope_p21 = inv_slope(p2, p1);
const float inv_slope_p31 = inv_slope(p3, p1);
const float inv_slope_p32 = inv_slope(p3, p2);
float inv_slope1_max, inv_slope2_max;
float inv_slope2_min, inv_slope1_min;
if (inv_slope_p21 < inv_slope_p31) {
inv_slope1_max = inv_slope_p21;
inv_slope2_max = inv_slope_p31;
inv_slope2_min = inv_slope_p31;
inv_slope1_min = inv_slope_p32;
}
else {
inv_slope1_max = inv_slope_p31;
inv_slope2_max = inv_slope_p21;
inv_slope2_min = inv_slope_p32;
inv_slope1_min = inv_slope_p31;
}
draw_tri_flat_max(
p1, p2[1],
inv_slope1_max, inv_slope2_max,
callback, user_data);
draw_tri_flat_min(
p3, p2[1] + 1, /* avoid overlap */
inv_slope1_min, inv_slope2_min,
callback, user_data);
}
}
#undef ORDERED_SWAP
#undef ORDERED_SWAP_BY
#undef ORDER_VARS2
#undef ORDER_VARS3_BY
/** \} */
/* -------------------------------------------------------------------- */
/** \name 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)
@ -334,3 +512,5 @@ void BLI_bitmap_draw_2d_poly_v2i_n(
MEM_freeN(span_y);
MEM_freeN(node_x);
}
/** \} */