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test triangle rendered?

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veclavtlica
2026-09-13 22:30:19 +03:00
parent 4e1fa1ed1c
commit 578c4a6d4f
6 changed files with 193 additions and 3 deletions
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Common/gem.h
+45 -3
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@@ -6,6 +6,8 @@
#define COM_GEM_H
#include "mat.h"
#include "pnt.h"
#include "vec.h"
#include <stdint.h>
/* Projects vertex position to a clip space via reordered row-major MVP matrix.
@@ -37,6 +39,8 @@ static inline com_vec_t com_gem_vec_project_clip(com_mat_t a, com_vec_t b) {
/* TODO: If we clip test bounding volume of a model first we can skip
* all clipping whatsoever, which might hold true more often, than the cost of
* testing the volume. */
/* TODO: It should be possible to have results in pixel position, not -1 to 1.
*/
#define COM_GEM_VERTEX_UNCLIPPED (0 << 0)
#define COM_GEM_VERTEX_CLIPPED_X (1 << 0)
@@ -44,15 +48,53 @@ static inline com_vec_t com_gem_vec_project_clip(com_mat_t a, com_vec_t b) {
/* Attempt to project clip space vertex to NDC, reporting which component lies
* outside of view. Bit test against those per component. This is needed for
* determining new view-lying clipped triangles. */
static inline uint8_t com_gem_clip_vis_project(com_vec_t a, com_vec_t *out) {
static inline uint8_t com_gem_clip_vis_project(com_vec_t a, com_pnt_t *out) {
uint8_t mask;
if (a.s.x < -a.s.z || a.s.x > a.s.z)
mask ^= COM_GEM_VERTEX_CLIPPED_X;
if (a.s.y < -a.s.z || a.s.y > a.s.z)
mask ^= COM_GEM_VERTEX_CLIPPED_Y;
out->a[0] = com_fix_div(a.a[0], a.a[2]);
out->a[1] = com_fix_div(a.a[1], a.a[2]);
out->a[0] = com_fix_div(a.a[0], a.a[2]) / 480 + 240;
out->a[1] = com_fix_div(a.a[1], a.a[2]) / 640 + 320;
return mask;
}
static inline void com_gem_draw_triangle(com_pnt_t v0, com_pnt_t v1,
com_pnt_t v2, uint8_t *buffer) {
// 1. Compute the bounding box of the triangle
int minX = com_vec_min(com_vec_from(v0.s.x, v1.s.x, v2.s.x));
int minY = com_vec_min(com_vec_from(v0.s.y, v1.s.y, v2.s.y));
int maxX = com_vec_max(com_vec_from(v0.s.x, v1.s.x, v2.s.x));
int maxY = com_vec_max(com_vec_from(v0.s.y, v1.s.y, v2.s.y));
// 2. Clip the bounding box against screen dimensions to avoid out-of-bounds
// errors
// minX = CLAMP(minX, 0, 480 - 1);
// minY = CLAMP(minY, 0, HEIGHT - 1);
// maxX = CLAMP(maxX, 0, 480 - 1);
// maxY = CLAMP(maxY, 0, HEIGHT - 1);
// 3. Loop over all pixels inside the bounding box
for (int y = minY; y <= maxY; y++) {
for (int x = minX; x <= maxX; x++) {
com_pnt_t p = {.s = {x, y}};
// Test the pixel center against all 3 edges
int w0 = com_pnt_edge_orient(v1, v2, p);
int w1 = com_pnt_edge_orient(v2, v0, p);
int w2 = com_pnt_edge_orient(v0, v1, p);
// If the point is inside or on all edges, draw the pixel
// (Assumes Clockwise vertex ordering)
if (w0 >= 0 && w1 >= 0 && w2 >= 0) {
printf("%i, %i\n", y, x);
buffer[(y * 640 + x) * 4 + 0] = '#';
buffer[(y * 640 + x) * 4 + 1] = '#';
buffer[(y * 640 + x) * 4 + 2] = '#';
buffer[(y * 640 + x) * 4 + 3] = '#';
}
}
}
}
#endif