raycaster/raycaster.cpp

#include "raycaster.hpp"
#include "texture.hpp"
#include <algorithm>
#include "constants.hpp"

using namespace fmt;
using std::make_unique;

union ColorConv {
  struct {
    uint8_t r;
    uint8_t g;
    uint8_t b;
    uint8_t a;
  } as_color;
  uint32_t as_int;
};

inline uint32_t dumb_lighting(uint32_t pixel, double distance) {
  if(distance < 1.0) return pixel;

  ColorConv conv{.as_int=pixel};
  conv.as_color.r /= distance;
  conv.as_color.g /= distance;
  conv.as_color.b /= distance;

  return conv.as_int;
}


Raycaster::Raycaster(sf::RenderWindow& window, Matrix &map, int width, int height) :
  $view_texture({(unsigned int)width, (unsigned int)height}),
  $view_sprite($view_texture),
  $width(width), $height(height),
  $window(window),
  $map(map),
  spriteOrder($textures.NUM_SPRITES),
  spriteDistance($textures.NUM_SPRITES),
  ZBuffer(width)
{
  $view_sprite.setPosition({0, 0});
  $pixels = make_unique<RGBA[]>($width * $height);
  $textures.load_textures();
  $view_texture.setSmooth(false);
}

void Raycaster::set_position(int x, int y) {
  $view_sprite.setPosition({(float)x, (float)y});
}

void Raycaster::position_camera(float player_x, float player_y) {
  // x and y start position
  $posX = player_x;
  $posY = player_y;
}

void Raycaster::draw_pixel_buffer() {
  $view_texture.update((uint8_t *)$pixels.get(), {(unsigned int)$width, (unsigned int)$height}, {0, 0});
  $window.draw($view_sprite);
}

void Raycaster::clear() {
  std::fill_n($pixels.get(), $width * $height, 0);
  $window.clear();
}

void Raycaster::sprite_casting() {
  const int textureWidth = TEXTURE_WIDTH;
  const int textureHeight = TEXTURE_HEIGHT;
  const int halfHeight = TEXTURE_HEIGHT / 2;

  // sort sprites from far to close
  for(int i = 0; i < $textures.NUM_SPRITES; i++) {
    auto& sprite = $textures.get_sprite(i);
    spriteOrder[i] = i;
    // this is just the distance calculation
    spriteDistance[i] = (($posX - sprite.x) *
        ($posX - sprite.x) +
        ($posY - sprite.y) *
        ($posY - sprite.y));
  }

  sort_sprites(spriteOrder, spriteDistance, $textures.NUM_SPRITES);

  // after sorting the sprites, do the projection
  for(int i = 0; i < $textures.NUM_SPRITES; i++) {
    int sprite_index = spriteOrder[i];
    Sprite& sprite_rec = $textures.get_sprite(sprite_index);
    // auto& sprite_texture = $textures.get_texture(sprite_rec.texture);
    sf::Sprite *sf_sprite = sprite_rec.sprite;

    double spriteX = sprite_rec.x - $posX;
    double spriteY = sprite_rec.y - $posY;

    //transform sprite with the inverse camera matrix
    // [ $planeX   $dirX ] -1                                       [ $dirY      -$dirX ]
    // [               ]       =  1/($planeX*$dirY-$dirX*$planeY) *   [                 ]
    // [ $planeY   $dirY ]                                          [ -$planeY  $planeX ]

    double invDet = 1.0 / ($planeX * $dirY - $dirX * $planeY); // required for correct matrix multiplication

    double transformX = invDet * ($dirY * spriteX - $dirX * spriteY);
    //this is actually the depth inside the screen, that what Z is in 3D, the distance of sprite to player, matching sqrt(spriteDistance[i])

    double transformY = invDet * (-$planeY * spriteX + $planeX * spriteY);

    int spriteScreenX = int(($width / 2) * (1 + transformX / transformY));

    // calculate the height of the sprite on screen
    //using "transformY" instead of the real distance prevents fisheye
    int spriteHeight = abs(int($height / transformY)) / sprite_rec.vDiv;

    // calculate width the the sprite
    // same as height of sprite, given that it's square
    int spriteWidth = abs(int($height / transformY)) / sprite_rec.uDiv;

    int drawStartX = -spriteWidth / 2 + spriteScreenX;
    if(drawStartX < 0) drawStartX = 0;
    int drawEndX = spriteWidth / 2 + spriteScreenX;
    if(drawEndX > $width) drawEndX = $width;

    int stripe = drawStartX;
    for(; stripe < drawEndX; stripe++) {
      //the conditions in the if are:
      //1) it's in front of camera plane so you don't see things behind you
      //2) ZBuffer, with perpendicular distance
      if(!(transformY > 0 && transformY < ZBuffer[stripe])) break;
    }

    int texX_end = int(textureWidth * (stripe - (-spriteWidth / 2 + spriteScreenX)) * textureWidth / spriteWidth) / textureWidth;

    if(drawStartX < drawEndX && transformY > 0 && transformY < ZBuffer[drawStartX]) {
      int vMoveScreen = int(sprite_rec.elevation * -1 / transformY);
      //calculate lowest and highest pixel to fill in current stripe
      int drawStartY = -spriteHeight / 2 + $height / 2 + vMoveScreen;
      if(drawStartY < 0) drawStartY = 0;
      int drawEndY = spriteHeight / 2 + $height / 2 + vMoveScreen;
      if(drawEndY >= $height) drawEndY = $height - 1;

      int texX = int(textureWidth * (drawStartX - (-spriteWidth / 2 + spriteScreenX)) * textureWidth / spriteWidth) / textureWidth;

      float x = float(drawStartX + RAY_VIEW_X);
      float y = float(drawStartY + RAY_VIEW_Y);
      float sprite_w = float(spriteWidth) / float(textureWidth);
      float sprite_h = float(spriteHeight) / float(textureHeight);

      int d = (y - vMoveScreen) * textureHeight - $height * halfHeight + spriteHeight * halfHeight;
      int texY = ((d * textureHeight) / spriteHeight) / textureHeight;

      sf_sprite->setScale({sprite_w, sprite_h});
      sf_sprite->setTextureRect(sf::IntRect({texX, texY}, {texX_end - texX, textureHeight}));
      sf_sprite->setPosition({x, y});
      $window.draw(*sf_sprite);
    }
  }
}

void Raycaster::cast_rays() {
  constexpr static const int textureWidth = TEXTURE_WIDTH;
  constexpr static const int textureHeight = TEXTURE_HEIGHT;
  double perpWallDist;

  // WALL CASTING
  for(int x = 0; x < $width; x++) {
    // calculate ray position and direction
    double cameraX = 2 * x / double($width) - 1; // x-coord in camera space
    double rayDirX = $dirX + $planeX * cameraX;
    double rayDirY = $dirY + $planeY * cameraX;

    // which box of the map we're in
    int mapX = int($posX);
    int mapY = int($posY);

    // length of ray from current pos to next x or y-side
    double sideDistX;
    double sideDistY;

    // length of ray from one x or y-side to next x or y-side
    double deltaDistX = std::abs(1.0 / rayDirX);
    double deltaDistY = std::abs(1.0 / rayDirY);

    int stepX = 0;
    int stepY = 0;
    int hit = 0;
    int side = 0;

    // calculate step and initial sideDist
    if(rayDirX < 0) {
      stepX = -1;
      sideDistX = ($posX - mapX) * deltaDistX;
    } else {
      stepX = 1;
      sideDistX = (mapX + 1.0 - $posX) * deltaDistX;
    }

    if(rayDirY < 0) {
      stepY = -1;
      sideDistY = ($posY - mapY) * deltaDistY;
    } else {
      stepY = 1;
      sideDistY = (mapY + 1.0 - $posY) * deltaDistY;
    }

    // perform DDA
    while(hit == 0) {
      if(sideDistX < sideDistY) {
        sideDistX += deltaDistX;
        mapX += stepX;
        side = 0;
      } else {
        sideDistY += deltaDistY;
        mapY += stepY;
        side = 1;
      }

      if($map[mapY][mapX] > 0) hit = 1;
    }

    if(side == 0) {
      perpWallDist = (sideDistX - deltaDistX);
    } else {
      perpWallDist = (sideDistY - deltaDistY);
    }

    int lineHeight = int($height / perpWallDist);

    int drawStart = -lineHeight / 2 + $height / 2 + $pitch;
    if(drawStart < 0) drawStart = 0;

    int drawEnd = lineHeight / 2 + $height / 2 + $pitch;
    if(drawEnd >= $height) drawEnd = $height - 1;

    auto texture = $textures.get_texture($map[mapY][mapX] - 1);

    // calculate value of wallX
    double wallX;  // where exactly the wall was hit
    if(side == 0) {
      wallX = $posY + perpWallDist * rayDirY;
    } else {
      wallX = $posX + perpWallDist * rayDirX;
    }
    wallX -= floor((wallX));

    // x coorindate on the texture
    int texX = int(wallX * double(textureWidth));
    if(side == 0 && rayDirX > 0) texX = textureWidth - texX - 1;
    if(side == 1 && rayDirY < 0) texX = textureWidth - texX - 1;

    // LODE: an integer-only bresenham or DDA like algorithm could make the texture coordinate stepping faster

    // How much to increase the texture coordinate per screen pixel
    double step = 1.0 * textureHeight / lineHeight;
    // Starting texture coordinate
    double texPos = (drawStart - $pitch - $height / 2 + lineHeight / 2) * step;

    for(int y = drawStart; y < drawEnd; y++) {
      int texY = (int)texPos & (textureHeight - 1);
      texPos += step;
      RGBA pixel = texture[textureHeight * texY + texX];
      $pixels[pixcoord(x, y)] = dumb_lighting(pixel, perpWallDist);
    }

    // SET THE ZBUFFER FOR THE SPRITE CASTING
    ZBuffer[x] = perpWallDist;
  }
}

void Raycaster::draw_ceiling_floor() {
  constexpr static const int textureWidth = TEXTURE_WIDTH;
  constexpr static const int textureHeight = TEXTURE_HEIGHT;

  for(int y = $height / 2 + 1; y < $height; ++y) {
    // rayDir for leftmost ray (x=0) and rightmost (x = w)
    float rayDirX0 = $dirX - $planeX;
    float rayDirY0 = $dirY - $planeY;
    float rayDirX1 = $dirX + $planeX;
    float rayDirY1 = $dirY + $planeY;

    // current y position compared to the horizon
    int p = y - $height / 2;

    // vertical position of the camera
    // 0.5 will the camera at the center horizon. For a
    // different value you need a separate loop for ceiling
    // and floor since they're no longer symmetrical.
    float posZ = 0.5 * $height;

    // horizontal distance from the camera to the floor for the current row
    // 0.5 is the z position exactly in the middle between floor and ceiling
    // See NOTE in Lode's code for more.
    float rowDistance = posZ / p;

    // calculate the real world step vector we have to add for each x (parallel to camera plane)
    // adding step by step avoids multiplications with a wight in the inner loop
    float floorStepX = rowDistance * (rayDirX1 - rayDirX0) / $width;
    float floorStepY = rowDistance * (rayDirY1 - rayDirY0) / $width;


    // real world coordinates of the leftmost column.
    // This will be updated as we step to the right
    float floorX = $posX + rowDistance * rayDirX0;
    float floorY = $posY + rowDistance * rayDirY0;

    auto floor_texture = (const uint32_t *)$textures.floor.getPixelsPtr();
    auto ceiling_texture = (const uint32_t *)$textures.ceiling.getPixelsPtr();

    for(int x = 0; x < $width; ++x) {
      // the cell coord is simply taken from the int parts of
      // floorX and floorY.
      int cellX = int(floorX);
      int cellY = int(floorY);

      // get the texture coordinat from the fractional part
      int tx = int(textureWidth * (floorX - cellX)) & (textureWidth - 1);
      int ty = int(textureWidth * (floorY - cellY)) & (textureHeight - 1);

      floorX += floorStepX;
      floorY += floorStepY;

      // now get the pixel from the texture
      uint32_t color;
      // this uses the previous ty/tx fractional parts of
      // floorX cellX to find the texture x/y. How?

      // FLOOR
      color = floor_texture[textureWidth * ty + tx];
      $pixels[pixcoord(x, y)] = color;

      // CEILING
      color = ceiling_texture[textureWidth * ty + tx];
      $pixels[pixcoord(x, $height - y - 1)] = color;
    }
  }
}

void Raycaster::render() {
  draw_ceiling_floor();
  cast_rays();
  draw_pixel_buffer();
  sprite_casting();
}

bool Raycaster::empty_space(int new_x, int new_y) {
  dbc::check((size_t)new_x < matrix::width($map),
      format("x={} too wide={}", new_x, matrix::width($map)));
  dbc::check((size_t)new_y < matrix::height($map),
      format("y={} too high={}", new_y, matrix::height($map)));

  return $map[new_y][new_x] == 0;
}


void Raycaster::sort_sprites(std::vector<int>& order, std::vector<double>& dist, int amount)
{
  std::vector<std::pair<double, int>> sprites(amount);

  for(int i = 0; i < amount; i++) {
    sprites[i].first = dist[i];
    sprites[i].second = order[i];
  }

  std::sort(sprites.begin(), sprites.end());

  // restore in reverse order
  for(int i = 0; i < amount; i++) {
    dist[i] = sprites[amount - i - 1].first;
    order[i] = sprites[amount - i - 1].second;
  }
}

void Raycaster::run(double speed, int dir) {
  double speed_and_dir = speed * dir;
  if(empty_space(int($posX + $dirX * speed_and_dir), int($posY))) {
    $posX += $dirX * speed_and_dir;
  }

  if(empty_space(int($posX), int($posY + $dirY * speed_and_dir))) {
      $posY += $dirY * speed_and_dir;
  }
}

void Raycaster::rotate(double speed, int dir) {
  double speed_and_dir = speed * dir;
  double oldDirX = $dirX;
  $dirX = $dirX * cos(speed_and_dir) - $dirY * sin(speed_and_dir);
  $dirY = oldDirX * sin(speed_and_dir) + $dirY * cos(speed_and_dir);

  double oldPlaneX = $planeX;
  $planeX = $planeX * cos(speed_and_dir) - $planeY * sin(speed_and_dir);
  $planeY = oldPlaneX * sin(speed_and_dir) + $planeY * cos(speed_and_dir);
}