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| -rw-r--r-- | tri.c | 114 |
1 files changed, 114 insertions, 0 deletions
@@ -0,0 +1,114 @@ +#include <stdio.h> +#include <stdlib.h> + +typedef struct { + int x, y; + int dx, dy; + int sx, sy; + int e; +} Line; + +void init_line( + Line* l, + const int* f, + const int* t +) { + const int dx = abs(t[0] - f[0]); + const int dy = -abs(t[1] - f[1]); + l->e = dx + dy; + l->dx = dx; + l->dy = dy; + l->sx = f[0] < t[0]? 1: -1; + l->sy = f[1] < t[1]? 1: -1; + l->x = f[0]; + l->y = f[1]; +} + +void step_line(Line* l) { + const int e2 = l->e * 2; + const int dx = l->dx; + const int dy = l->dy; + if (e2 > dy) { + l->e += dy; + l->x += l->sx; + } + if (e2 <= dx) { + l->e += dx; + l->y += l->sy; + } +} + +int tri_hand( + const int* v0, + const int* v1, + const int* v2 +) { + return + (v1[0] - v0[0]) * (v2[1] - v0[1]) - + (v2[0] - v0[0]) * (v1[1] - v0[1]) > 0; +} + +void fill_tri( + char* buf, int w, + const int* v0, + const int* v1, + const int* v2 +) { + Line ne, fe; + const int* t; + int ha, x; +#define swap(a, b) { \ + t = a; \ + a = b; \ + b = t; \ +} + if (v0[1] > v1[1]) + swap(v0, v1); + if (v1[1] > v2[1]) + swap(v1, v2); + if (v0[1] > v1[1]) + swap(v0, v1); +#undef swap + ha = tri_hand(v0, v1, v2); + if (ha) { + init_line(&ne, v0, v2); + init_line(&fe, v0, v1); + } else { + init_line(&ne, v0, v1); + init_line(&fe, v0, v2); + } +#define scanline \ + for (x = ne.x; x < fe.x; x++) \ + buf[x + fe.y * w] = '#'; \ + step_line(&fe); \ + while (ne.y != fe.y) \ + step_line(&ne); + while (fe.y < v1[1]) { + scanline + } + if (ha) + init_line(&fe, v1, v2); + else + init_line(&ne, v1, v2); + while (fe.y < v2[1]) { + scanline + } +#undef scanline +} + +int main(void) { + int v0[] = { 16, 2 }; + int v1[] = { 31, 16 }; + int v2[] = { 1, 30 }; + char buf[32*32]; + int i; + for (i = 0; i < 32*32; i++) + buf[i] = ' '; + fill_tri(buf, 32, v0, v1, v2); + for (i = 0; i < 32*32; i++) { + if (!(i & 31)) printf("\n"); + printf("%c", buf[i]); + } + printf("\n"); +} + |