Anti aliasing code for a rasteriser created using C++.

anti-aliasing.cpp

vec3 aliasing_buffer[SCREEN_HEIGHT][SCREEN_WIDTH];

screen *screen = InitializeSDL(SCREEN_WIDTH/3, SCREEN_HEIGHT/3, FULLSCREEN_MODE);

memset(screen->buffer , 0, screen->height * screen->width * sizeof(uint32_t));
memset(depth_buffer   , 0, SCREEN_HEIGHT  * SCREEN_WIDTH  * sizeof(float   ));
memset(aliasing_buffer, 0, SCREEN_HEIGHT  * SCREEN_WIDTH  * sizeof(vec3    ));

void draw_screen(screen* screen) {
  for (int y = 0; y < SCREEN_HEIGHT; y+=3) {
    for (int x = 0; x < SCREEN_WIDTH; x+=3) {
      vec3 average = (aliasing_buffer[y][x  ] + aliasing_buffer[y+1][x  ] + aliasing_buffer[y+2][x  ]
                    + aliasing_buffer[y][x+1] + aliasing_buffer[y+1][x+1] + aliasing_buffer[y+2][x+1]
                    + aliasing_buffer[y][x+2] + aliasing_buffer[y+1][x+2] + aliasing_buffer[y+2][x+2]) / 9.f;
      PutPixelSDL(screen, int(x/3), int(y/3), average);
    }
  }
}

if (x >= 0 && x < SCREEN_WIDTH && y >= 0 && y < SCREEN_HEIGHT) {
  if (p.z_inv > depth_buffer[y][x]) {
    depth_buffer[y][x] = p.z_inv;
    aliasing_buffer[y][x] = R;
  }
}