218 lines
6.9 KiB
C++
218 lines
6.9 KiB
C++
/* Things to do:
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OK Drawing triangles
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OK Drawing cubes and lines for testing
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OK Y up coordinate system, left handed
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OK Drawing a cube with perspective
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OK Culling triangles facing away from camera
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OK Texture mapping
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? Basic math operations on Vec4 Mat4 - Muls, Dot, Cross etc.
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OK Basic linear transformations - rotation, translation, scaling
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* Bilinear filtering of textures / subpixel precison
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* Perspective matrix vs simple perspective
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* Perspective correct interpolation
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* Depth buffer
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* FPS Camera
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* Reading OBJ files
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* Rendering multiple objects, queue renderer
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* Clipping
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* Optimizations
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* SIMD
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* Multithreading
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*
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*/
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#include "main.h"
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#include "platform.h"
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#include "math.h"
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#include "stb_image.h"
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// TODO:
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// Perspective correct interpolation
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// Camera
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// Perspective projection
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// Texture mapping
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// Reading OBJ
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struct Face {
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int p[3];
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Vec2 tex[3];
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};
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Vec3 cube_vertices[] = {
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{-1, -1,-1},
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{-1, 1, -1},
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{1, 1, -1},
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{1, -1, -1},
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{1, 1, 1},
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{1, -1, 1},
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{-1, 1, 1},
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{-1, -1,1},
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};
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Face cube_faces[] = {
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{{1, 2, 3}, {{ 0, 0 }, { 0, 1 }, { 1, 1 }}, },
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{{1, 3, 4}, {{ 0, 0 }, { 1, 1 }, { 1, 0 }}, },
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{{4, 3, 5}, {{ 0, 0 }, { 0, 1 }, { 1, 1 }}, },
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{{4, 5, 6}, {{ 0, 0 }, { 1, 1 }, { 1, 0 }}, },
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{{6, 5, 7}, {{ 0, 0 }, { 0, 1 }, { 1, 1 }}, },
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{{6, 7, 8}, {{ 0, 0 }, { 1, 1 }, { 1, 0 }}, },
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{{8, 7, 2}, {{ 0, 0 }, { 0, 1 }, { 1, 1 }}, },
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{{8, 2, 1}, {{ 0, 0 }, { 1, 1 }, { 1, 0 }}, },
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{{2, 7, 5}, {{ 0, 0 }, { 0, 1 }, { 1, 1 }}, },
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{{2, 5, 3}, {{ 0, 0 }, { 1, 1 }, { 1, 0 }}, },
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{{6, 8, 1}, {{ 0, 0 }, { 0, 1 }, { 1, 1 }}, },
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{{6, 1, 4}, {{ 0, 0 }, { 1, 1 }, { 1, 0 }}, }
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};
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FUNCTION
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void DrawRect(Image* dst, float X, float Y, float w, float h, uint32_t color) {
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int max_x = (int)(MIN(X + w, dst->x) + 0.5f);
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int max_y = (int)(MIN(Y + h, dst->y) + 0.5f);
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int min_x = (int)(MAX(0, X) + 0.5f);
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int min_y = (int)(MAX(0, Y) + 0.5f);
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for (int y = min_y; y < max_y; y++) {
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for (int x = min_x; x < max_x; x++) {
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dst->pixels[x + (dst->y - 1 - y) * dst->x] = color;
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}
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}
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}
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FUNCTION
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float EdgeFunction(Vec4 vecp0, Vec4 vecp1, Vec4 p) {
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float result = (vecp1.y - vecp0.y) * (p.x - vecp0.x) - (vecp1.x - vecp0.x) * (p.y - vecp0.y);
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return result;
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}
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FUNCTION
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void DrawTriangle(Image* dst, Image *src, Vec4 p0, Vec4 p1, Vec4 p2,
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Vec2 tex0, Vec2 tex1, Vec2 tex2) {
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float min_x = (float)(MIN(p0.x, MIN(p1.x, p2.x)));
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float min_y = (float)(MIN(p0.y, MIN(p1.y, p2.y)));
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float max_x = (float)(MAX(p0.x, MAX(p1.x, p2.x)));
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float max_y = (float)(MAX(p0.y, MAX(p1.y, p2.y)));
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min_x = MAX(0, min_x) + 0.5f;
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min_y = MAX(0, min_y) + 0.5f;
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max_x = MIN(dst->x-1, max_x) + 0.5f;
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max_y = MIN(dst->y-1, max_y) + 0.5f;
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//@Todo: Fix the proper rounding
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//@Todo: Determine whether we need subprecision etc
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float area = EdgeFunction(p0, p1, p2);
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for (int y = min_y; y < max_y; y++) {
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for (int x = min_x; x < max_x; x++) {
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float edge1 = EdgeFunction(p0, p1, { (float)x,(float)y });
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float edge2 = EdgeFunction(p1, p2, { (float)x,(float)y });
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float edge3 = EdgeFunction(p2, p0, { (float)x,(float)y });
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if (edge1 >= 0 && edge2 >= 0 && edge3 >= 0) {
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float w1 = edge2 / area;
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float w2 = edge3 / area;
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float w3 = edge1 / area;
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#if 1
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float u = tex0.x * (w1 / p0.w) + tex1.x * (w2 / p1.w) + tex2.x * (w3 / p2.w);
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float v = tex0.y * (w1 / p0.w) + tex1.y * (w2 / p1.w) + tex2.y * (w3 / p2.w);
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float interpolated_z = (1.f / p0.w) * w1 + (1.f / p1.w) * w2 + (1.f / p2.w) * w3;
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u /= interpolated_z;
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v /= interpolated_z;
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#else
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float u = tex0.x * w1 + tex1.x * w2 + tex2.x * w3;
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float v = tex0.y * w1 + tex1.y * w2 + tex2.y * w3;
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#endif
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int ui = (int)(u * (src->x - 1) + 0.5f);
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int vi = (int)(v * (src->y - 1) + 0.5f);
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uint32_t pixel = src->pixels[ui + (src->y - 1 - vi) * src->x];
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dst->pixels[x + (dst->y - 1 - y) * dst->x] = pixel;
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}
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}
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}
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DrawRect(dst, p0.x-4, p0.y-4, 8,8, 0x00ff0000);
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DrawRect(dst, p1.x-4, p1.y-4, 8,8, 0x0000ff00);
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DrawRect(dst, p2.x-4, p2.y-4, 8,8, 0x000000ff);
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}
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FUNCTION
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void DrawLine(Image *dst, float x0, float y0, float x1, float y1) {
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float delta_x = (x1 - x0);
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float delta_y = (y1 - y0);
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float longest_side_length = (fabsf(delta_x) >= fabsf(delta_y)) ? fabsf(delta_x) : fabsf(delta_y);
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float x_inc = delta_x / (float)longest_side_length;
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float y_inc = delta_y / (float)longest_side_length;
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float current_x = (float)x0;
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float current_y = (float)y0;
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for (int i = 0; i <= longest_side_length; i++) {
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int x = (int)(current_x + 0.5f);
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int y = (int)(current_y + 0.5f);
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dst->pixels[x + (dst->y - 1 - y) * dst->x] = 0xffffffff;
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current_x += x_inc;
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current_y += y_inc;
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}
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}
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int main() {
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OS_Init({.window_x=1280, .window_y=720});
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float rotation = 0;
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Vec3 camera_pos = {0,0,-5};
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int x,y,n;
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unsigned char *data = stbi_load("assets/cat.png", &x, &y, &n, 4);
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Image img = {(uint32_t *)data, x, y};
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Mat4 perspective = Mat4Perspective(60.f, screen.x, screen.y, 0.1f, 100.f);
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while (OS_GameLoop()) {
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for (int y = 0; y < screen.y; y++) {
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for (int x = 0; x < screen.x; x++) {
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screen.pixels[x + y * screen.x] = 0;
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}
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}
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#if 0
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DrawTriangle(&screen, &img, { 100,100 }, { 100,400 }, { 400,400 }, { 0,0 }, { 0,1 }, { 1,1 });
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DrawTriangle(&screen, &img, { 100,100 }, { 400,400 }, { 400,100}, { 0,0 }, { 1,1 }, { 1,0 });
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#else
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Mat4 transform = Mat4RotationZ(rotation);
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transform = transform * Mat4RotationX(rotation);
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if (keydown_a) rotation += 0.05f;
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if (keydown_b) rotation -= 0.05f;
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for (int i = 0; i < ARRAY_CAP(cube_faces); i++) {
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Face* face = cube_faces + i;
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Vec4 pos[3] = {
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vec4(cube_vertices[face->p[0] - 1], 1),
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vec4(cube_vertices[face->p[1] - 1], 1),
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vec4(cube_vertices[face->p[2] - 1], 1),
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};
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//@Note: Transform
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for (int j = 0; j < 3; j++) {
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pos[j] = transform * pos[j];
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}
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//@Note: Cull
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Vec3 p0_to_camera = camera_pos - pos[0].xyz;
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Vec3 p0_to_p1 = pos[1].xyz - pos[0].xyz;
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Vec3 p0_to_p2 = pos[2].xyz - pos[0].xyz;
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Vec3 normal = Cross(p0_to_p1, p0_to_p2);
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if (Dot(normal, p0_to_camera) > 0) {
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for (int j = 0; j < 3; j++) {
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//@Note: Camera
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pos[j].xyz = pos[j].xyz - camera_pos;
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//@Note: Perspective
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pos[j] = perspective * pos[j];
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pos[j].x = pos[j].x / pos[j].w;
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pos[j].y = pos[j].y / pos[j].w;
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pos[j].z = pos[j].z / pos[j].w;
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//@Note: To pixel space
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pos[j].x *= screen.x / 2;
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pos[j].y *= screen.y / 2;
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pos[j].x += screen.x / 2;
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pos[j].y += screen.y / 2;
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}
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DrawTriangle(&screen, &img, pos[0], pos[1], pos[2], face->tex[0], face->tex[1], face->tex[2]);
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//DrawLine(&screen, pos[0].x, pos[0].y, pos[1].x, pos[1].y);
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//DrawLine(&screen, pos[1].x, pos[1].y, pos[2].x, pos[2].y);
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//DrawLine(&screen, pos[2].x, pos[2].y, pos[0].x, pos[0].y);
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}
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}
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#endif
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}
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}
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