compute intersections

src/engine.rs

@@ -3,32 +3,52 @@ use piston_window::*;
 
 use std::f64::consts::*;
 
-#[derive(PartialEq, Debug)]
+#[derive(Copy, Clone, PartialEq, Debug)]
 struct Position {
     x: f64,
     y: f64,
 }
 
-struct Player {
-   pos: Position,
-   angle: f64, // radian or degree
+impl Position {
+    pub fn distance(&self, other: Position) -> f64 {
+        ((self.x - other.x).powi(2) + (self.y - other.y).powi(2)).sqrt()
     }
 
+    pub fn distance_sqr(&self, other: Position) -> f64 {
+        (self.x - other.x).powi(2) + (self.y - other.y.powi(2))
+    }
+}
+
+type Degree = f64;
+type Radian = f64;
+
+struct Player {
+   pos: Position,
+   angle: Degree,
+}
+
+#[derive(Copy, Clone, PartialEq)]
 pub enum Tile {
     Empty,
     Wall,
 }
 
 pub struct Level {
-    pub width: u16,
-    pub height: u16,
+    pub width: usize,
+    pub height: usize,
     pub tiles: Vec<Tile>,
 }
 
+impl Level {
+    pub fn contains(&self, pos: Position) -> bool {
+        0.0 <= pos.x && pos.x <= self.width as f64 && 0.0 <= pos.y && pos.y <= self.height as f64
+    }
+}
+
 pub struct Engine {
     w: f64,
     h: f64,
-    horiz_fov: f64,
+    horiz_fov: Degree,
     player: Player,
     level: Level,
 }
@@ -51,25 +71,77 @@ impl Engine {
         }
     }
 
-    fn closest_point(pos: &Position, angle: f64) -> (Tile, Position) {
-        // First let's find the closest intersections with the grid
-        let dx = angle.cos();
-        let x_dist = if dx > 0.0 { 1.0 - pos.x.fract() } else { pos.x.fract() };
-        let x_relative_dist = x_dist / dx.abs();
-        let dy = angle.sin();
-        let y_dist = if dy > 0.0 { 1.0 - pos.y.fract() } else { pos.y.fract() };
-        let y_relative_dist = y_dist / dy.abs();
-        if x_relative_dist > y_relative_dist {
-            // first grid hit is horizontal line
+    fn closest_point(level: &Level, pos: &Position, angle: Radian) -> (Tile, Position) {
+        let (y_step, x_step) = match angle {
+            0.0 => (0.0, std::f64::INFINITY),
+            90.0 => (std::f64::INFINITY, 0.0),
+            180.0 => (0.0, std::f64::NEG_INFINITY),
+            270.0 => (std::f64::NEG_INFINITY, 0.0),
+            x if (0.0..(PI * 0.5)).contains(&x) => (angle.tan(), ((PI / 2.0) - angle).tan()),
+            x if ((PI * 0.5)..PI).contains(&x) => ((PI - x).tan(), -((x - (PI / 2.0)).tan())),
+            x if (PI..(PI * 1.5)).contains(&x) => (-((x - PI).tan()), -(((PI * 1.5) - x).tan())),
+            x if ((PI * 1.5)..(PI * 2.0)).contains(&x) => (((PI * 2.0) - x).tan(), -((x - (PI * 1.5)).tan())),
+            _ => panic!("Invalid angle value {}.", angle),
+        };
+
+        let (x_remain, y_remain) = match (x_step, y_step) {
+            (x, y) if x >= 0.0 && y >= 0.0 => (1.0 - pos.x.fract(), 1.0 - pos.y.fract()),
+            (x, y) if x <= 0.0 && y >= 0.0 => (-pos.x.fract(), 1.0 - pos.y.fract()),
+            (x, y) if x >= 0.0 && y <= 0.0 => (1.0 - pos.x.fract(), -pos.y.fract()),
+            (x, y) if x <= 0.0 && y <= 0.0 => (-pos.x.fract(), -pos.y.fract()),
+            _ => panic!("Invalid steps"),
+        };
+
+        let x_dist_factor = x_remain / x_step;
+        let y_dist_factor = y_remain / y_step;
+
+        let mut x_candidate = Position {
+            x: pos.x + x_remain, // x_remain = x_step * x_dist_factor
+            y: pos.y + y_step * x_dist_factor,
+        };
+        let mut y_candidate = Position {
+            x: pos.x + x_step * y_dist_factor,
+            y: pos.y + y_remain, // y_remain = y_step * y_dist_factor
+        };
+
+        let mut next_point: Position = *pos;
+        let mut tile = Tile::Empty;
+
+        while tile == Tile::Empty && level.contains(next_point) {
+            if next_point.distance(x_candidate) < next_point.distance(y_candidate) {
+                next_point = x_candidate;
+                x_candidate = Position {
+                    x: x_candidate.x + x_step.signum(),
+                    y: x_candidate.y + y_step,
+                };
             } else {
-            // first grid hit is vertical line
+                next_point = y_candidate;
+                y_candidate = Position {
+                    x: y_candidate.x + x_step,
+                    y: y_candidate.y + y_step.signum(),
+                };
             }
 
-        // see Game Engine Black Book
-        let xstep = angle.tan();
-        let ystep = ((PI / 2.0) - angle).tan();
+            tile = if next_point.x.fract() == 0.0 {
+                let x_index = (next_point.x.trunc() + x_step.signum()) as usize;
+                assert!(x_index < level.width);
+                let y_index = next_point.y.trunc() as usize;
+                assert!(y_index < level.height);
+                let index: usize = x_index + y_index * level.width;
+                level.tiles[index]
+            } else {
+                let x_index = next_point.x.trunc() as usize;
+                assert!(x_index < level.width);
+                let y_index = (next_point.y.trunc() + y_step.signum()) as usize;
+                assert!(y_index < level.height);
+                let index: usize = x_index + y_index * level.width;
+                level.tiles[index]
+            };
+        }
 
-        (Tile::Empty, Position {x: 2., y: 2.})
+        assert!(tile != Tile::Empty);
+
+       (tile, next_point)
     }
 
     pub fn render(&mut self, context: Context, graphics: &mut G2d) {
@@ -99,7 +171,22 @@ impl Engine {
         let width = self.w as i32;
         for n in 0..width {
             //   cast a ray
-            let (tile, pos) = Engine::closest_point(&self.player.pos, ray_angle);
+            let ray_radian = ray_angle.to_radians();
+            let (tile, pos) = Engine::closest_point(&self.level, &self.player.pos, ray_radian);
+            let distance = self.player.pos.distance(pos);
+            let player_space_distance = (self.player.pos.x - pos.x).abs() * ray_radian.cos()
+                - (self.player.pos.y - pos.y).abs() * ray_radian.sin();
+            if tile == Tile::Wall {
+                println!("ray: {}, wall at {:?}, distance: {}", n, pos, distance);
+                let wall_height = (self.h / (distance * 3.0)).min(self.h);
+                let wall_color = [0.9, 0.2, 0.2, 1.0];
+                println!("wall height: {}", wall_height);
+                rectangle(wall_color,
+                          [n as f64, (self.h - wall_height) / 2.0, (n + 1) as f64, wall_height],
+                          context.transform,
+                          graphics);
+
+            };
             //   see what wall it hits
             //   compute wall height
             //   draw wall portion