add rotating cheese

This adds the Cheese3D graphics api and makes the cheese command display a cheese rotating in 3d as a demo

1 files changed, 148 insertions, 0 deletions

diff --git a/stage3/cheese3d.c b/stage3/cheese3d.c
new file mode 100644
index 0000000..154ce58
--- /dev/null
+++ b/stage3/cheese3d.c
@@ -0,0 +1,148 @@
+#include "heap.h"
+#include "math3d.h"
+#include "cheese3d.h"
+#include "gfx.h"
+#include "memory.h"
+
+cheese3d_ctx cheese3d_create(u32 width, u32 height, u32 pitch, u32 bgcolor)
+{
+	return (cheese3d_ctx) {
+		.width = width,
+		.height = height,
+		.pitch = pitch,
+		.bgcolor = bgcolor,
+		.depth_buffer = malloc(gfx_info->width * gfx_info->height * sizeof(u32)),
+		.color_buffer = malloc(gfx_info->pitch * gfx_info->height),
+	};
+}
+
+cheese3d_ctx cheese3d_create_default(u32 bgcolor)
+{
+	return cheese3d_create(gfx_info->width, gfx_info->height, gfx_info->pitch, bgcolor);
+}
+
+void cheese3d_destroy(cheese3d_ctx ctx)
+{
+	free(ctx.depth_buffer);
+	free(ctx.color_buffer);
+}
+
+void cheese3d_clear(cheese3d_ctx ctx, bool color, bool depth)
+{
+	for (u32 x = 0; x < gfx_info->width; x++)
+	for (u32 y = 0; y < gfx_info->height; y++) {
+		if (color) ctx.depth_buffer[y * ctx.width + x] = 0.0;
+		if (depth) *(u32 *) (ctx.color_buffer + y * ctx.pitch + x * sizeof(u32)) = ctx.bgcolor;
+	}
+}
+
+void cheese3d_render(cheese3d_ctx ctx, usize num, vertex *vertices, texture *textures, float transform[4][4])
+{
+	for (usize i = 0; i < num; i += 3) {
+		float verts[3][4];
+		float min[2];
+		float max[2];
+
+		for (usize j = 0; j < 3; j++) {
+			float coord[4];
+			for (int k = 0; k < 3; k++)
+				coord[k] = vertices[i+j].pos[k];
+			coord[3] = 1.0;
+
+			mat_mul_vec(transform, coord);
+
+			verts[j][3] = 1/coord[3];
+			for (int k = 0; k < 3; k++)
+				verts[j][k] = coord[k] * verts[j][3];
+
+			for (int k = 0; k < 2; k++) {
+				if (j == 0 || verts[j][k] > max[k])
+					max[k] = verts[j][k];
+				if (j == 0 || verts[j][k] < min[k])
+					min[k] = verts[j][k];
+			}
+		}
+
+		// cull clockwise faces
+		float area = tri_area(verts[0], verts[1], verts[2]);
+		if (area < 0)
+			continue;
+
+		i32 i_min[2];
+		i32 i_max[2];
+		for (int k = 0; k < 2; k++) {
+			i32 size = k ? gfx_info->height : gfx_info->width;
+
+			i_min[k] = (0.5 + 0.5 * min[k]) * size;
+			i_max[k] = (0.5 + 0.5 * max[k]) * size;
+
+			if (i_max[k] >= size)
+				i_max[k] = size-1;
+			if (i_min[k] < 0)
+				i_min[k] = 0;
+		}
+
+		for (i32 y = i_min[1]; y <= i_max[1]; y++) {
+			float point[2] = {
+				0.0,
+				(float) y / gfx_info->height * 2.0 - 1.0
+			};
+			for (i32 x = i_min[0]; x <= i_max[0]; x++) {
+				point[0] = (float) x / gfx_info->width * 2.0 - 1.0;
+
+				float weights[3];
+				if ((weights[0] = tri_area(point, verts[1], verts[2])) < 0)
+					continue;
+				if ((weights[1] = tri_area(verts[0], point, verts[2])) < 0)
+					continue;
+				if ((weights[2] = tri_area(verts[0], verts[1], point)) < 0)
+					continue;
+
+				float depth = 0.0;
+				float w = 0.0;
+				float tex[2] = { 0.0, 0.0 };
+
+				for (int j = 0; j < 3; j++) {
+					weights[j] /= area;
+
+					depth += weights[j] * verts[j][2];
+					w += weights[j] * verts[j][3];
+					tex[0] += weights[j] * verts[j][3] * vertices[i+j].tex[0];
+					tex[1] += weights[j] * verts[j][3] * vertices[i+j].tex[1];
+				}
+
+				tex[0] /= w;
+				tex[1] /= w;
+
+				float *d = &ctx.depth_buffer[y * ctx.width + x];
+				if (*d > depth)
+					continue;
+				*d = depth;
+
+				texture *t = &textures[i];
+
+				i32 i_tex[2];
+				for (int k = 0; k < 2; k++) {
+					i32 size = k ? t->h : t->w;
+
+					i_tex[k] = tex[k] * size;
+
+					if (i_tex[k] >= size)
+						i_tex[k] = size-1;
+					if (i_tex[k] < 0)
+						i_tex[k] = 0;
+				}
+
+				*(u32 *) (ctx.color_buffer + y * ctx.pitch + x * sizeof(u32)) =
+					t->data[i_tex[1]*t->w+i_tex[0]];
+			}
+		}
+
+	}
+
+}
+
+void cheese3d_display(cheese3d_ctx ctx)
+{
+	memcpy((void *) (u64) gfx_info->framebuffer, ctx.color_buffer, gfx_info->pitch * gfx_info->height);
+}