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use crate::game::Game;
use crate::texture::TEX_SIZE;
pub struct Renderer {
screen_w: usize,
screen_h: usize,
/// Precomputed: floor_dist_lut[row] = perpendicular distance to floor at that row.
floor_dist_lut: Vec<f64>,
/// Precomputed: floor_bright_lut[row] = brightness × 256 for that row (fixed-point).
floor_bright_lut: Vec<u32>,
}
impl Renderer {
pub fn new(screen_w: usize, screen_h: usize) -> Self {
let half_h = screen_h as f64 / 2.0;
let mut floor_dist_lut = vec![0.0f64; screen_h];
let mut floor_bright_lut = vec![0u32; screen_h];
// Only rows below the horizon have meaningful floor values.
for py in (screen_h / 2 + 1)..screen_h {
let dy = py as f64 - half_h;
let dist = 0.5 * screen_h as f64 / dy;
floor_dist_lut[py] = dist;
let bright = (1.0 / (1.0 + dist * 0.15)).max(0.05);
floor_bright_lut[py] = (bright * 256.0) as u32;
}
Self {
screen_w,
screen_h,
floor_dist_lut,
floor_bright_lut,
}
}
/// Produce one frame into `buffer` (packed `0xAARRGGBB`).
pub fn render(&self, game: &Game, buffer: &mut [u32]) {
buffer.fill(0xFF00_0000); // pure-black ceiling
let half_h = self.screen_h as f64 / 2.0;
let fov = std::f64::consts::PI / 3.0; // 60°
for sx in 0..self.screen_w {
let cam_x = 2.0 * sx as f64 / self.screen_w as f64 - 1.0;
let ray_angle = game.player.angle + (fov / 2.0) * cam_x;
let rdx = ray_angle.cos();
let rdy = ray_angle.sin();
// Floor uses perpendicular distance from the LUT, but needs
// Euclidean distance for correct world-position projection.
// Scale by 1/cos(angle_diff) so that rdx_floor / rdy_floor
// map floor_dist → Euclidean travel along the ray.
let cos_diff = (ray_angle - game.player.angle).cos().abs().max(0.001);
let rdx_floor = rdx / cos_diff;
let rdy_floor = rdy / cos_diff;
// ---- DDA setup -------------------------------------------------
let mut map_x = game.player.x as isize;
let mut map_y = game.player.y as isize;
let ddx = if rdx == 0.0 {
f64::MAX
} else {
(1.0 / rdx).abs()
};
let ddy = if rdy == 0.0 {
f64::MAX
} else {
(1.0 / rdy).abs()
};
let (step_x, mut side_x) = if rdx < 0.0 {
(-1isize, (game.player.x - map_x as f64) * ddx)
} else {
(1isize, (map_x as f64 + 1.0 - game.player.x) * ddx)
};
let (step_y, mut side_y) = if rdy < 0.0 {
(-1isize, (game.player.y - map_y as f64) * ddy)
} else {
(1isize, (map_y as f64 + 1.0 - game.player.y) * ddy)
};
let mut hit_side: bool;
let euclidean: f64;
// ---- DDA loop --------------------------------------------------
loop {
if side_x < side_y {
side_x += ddx;
map_x += step_x;
hit_side = false;
} else {
side_y += ddy;
map_y += step_y;
hit_side = true;
}
if map_y < 0
|| map_y >= game.maze.height() as isize
|| map_x < 0
|| map_x >= game.maze.width() as isize
{
euclidean = 1.0;
break;
}
if game.maze.is_wall(map_y as usize, map_x as usize) {
euclidean = if !hit_side {
(map_x as f64 - game.player.x + (1.0 - step_x as f64) / 2.0) / rdx
} else {
(map_y as f64 - game.player.y + (1.0 - step_y as f64) / 2.0) / rdy
};
break;
}
}
// Fisheye correction
let perp_dist = (euclidean * (ray_angle - game.player.angle).cos().abs()).max(0.001);
// ---- wall slice ------------------------------------------------
let wall_h = (self.screen_h as f64 / perp_dist) as isize;
let draw_start = ((-wall_h / 2) + self.screen_h as isize / 2).max(0) as usize;
let draw_end = ((wall_h / 2) + self.screen_h as isize / 2)
.min(self.screen_h as isize - 1) as usize;
// Texture x-coordinate (uses Euclidean, not perp)
let wall_x = if !hit_side {
game.player.y + euclidean * rdy
} else {
game.player.x + euclidean * rdx
};
let wall_x = wall_x - wall_x.floor();
let tex_x = ((wall_x * TEX_SIZE as f64) as usize).min(TEX_SIZE - 1);
// Hoist: brightness is identical for every pixel in this column
let wall_bright_fx = {
let b = (1.0 / (1.0 + perp_dist * 0.12)).max(0.08);
(b * 256.0) as u32
};
for py in draw_start..=draw_end {
let tex_y = ((py as f64 - half_h + wall_h as f64 / 2.0) * TEX_SIZE as f64
/ wall_h as f64) as usize;
let tex_y = tex_y.min(TEX_SIZE - 1);
let color = game.wall_texture[tex_y * TEX_SIZE + tex_x];
buffer[py * self.screen_w + sx] = darken_fx(color, wall_bright_fx);
}
// ---- floor below the wall --------------------------------------
let floor_start = draw_end + 1;
if floor_start < self.screen_h {
for py in floor_start..self.screen_h {
let floor_dist = self.floor_dist_lut[py];
if floor_dist > 15.0 {
// Far floor → just a dark pixel, skip texture & world calc.
let gray = darken_fx(0xFF80_8080, self.floor_bright_lut[py]);
buffer[py * self.screen_w + sx] = gray;
} else {
let fx = game.player.x + floor_dist * rdx_floor;
let fy = game.player.y + floor_dist * rdy_floor;
let ftx = ((fx.fract().abs() * TEX_SIZE as f64) as usize).min(TEX_SIZE - 1);
let fty = ((fy.fract().abs() * TEX_SIZE as f64) as usize).min(TEX_SIZE - 1);
let color = game.floor_texture[fty * TEX_SIZE + ftx];
buffer[py * self.screen_w + sx] =
darken_fx(color, self.floor_bright_lut[py]);
}
}
}
}
}
}
/// Integer darken: `bright_fx` is brightness × 256 in fixed-point.
#[inline(always)]
fn darken_fx(color: u32, bright_fx: u32) -> u32 {
let r = (((color >> 16) & 0xFF) * bright_fx) >> 8;
let g = (((color >> 8) & 0xFF) * bright_fx) >> 8;
let b = ((color & 0xFF) * bright_fx) >> 8;
0xFF00_0000 | (r << 16) | (g << 8) | b
}
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