refactor dda

1 files changed, 63 insertions, 0 deletions

diff --git a/src/sim/lib/ray.rs b/src/sim/lib/ray.rs
new file mode 100644
index 0000000..52d5ba9
--- /dev/null
+++ b/src/sim/lib/ray.rs
@@ -0,0 +1,63 @@
+use glam::{IVec2, Vec2};
+
+// Amanatides and Woo's fast Voxel Traversal
+pub struct AwDda {
+    next: IVec2,
+    step_sign: IVec2,
+    step_delta: Vec2,
+    t_max: Vec2,
+}
+
+impl AwDda {
+    pub fn new(from: Vec2, to: Vec2) -> Self {
+        let first = from.round().as_ivec2();
+        // direction we step for each component on each iteration
+        let from_to_delta = to - from;
+        let step_sign = from_to_delta.signum().as_ivec2();
+
+        let step_delta = 1.0 / from_to_delta.abs();
+
+        let frac = Vec2::new(
+            if step_sign.x > 0 {
+                (first.x as f32 + 0.5) - from.x
+            } else {
+                from.x - (first.x as f32 - 0.5)
+            },
+            if step_sign.y > 0 {
+                (first.y as f32 + 0.5) - from.y
+            } else {
+                from.y - (first.y as f32 - 0.5)
+            },
+        );
+
+        let t_max = frac * step_delta;
+
+        AwDda {
+            next: first,
+            step_sign,
+            step_delta,
+            t_max,
+        }
+    }
+}
+
+impl Iterator for AwDda {
+    type Item = IVec2;
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.t_max.min_element() >= 1.0 {
+            return None;
+        }
+
+        let cur = self.next;
+
+        if self.t_max.x < self.t_max.y {
+            self.next.x += self.step_sign.x;
+            self.t_max.x += self.step_delta.x;
+        } else {
+            self.next.y += self.step_sign.y;
+            self.t_max.y += self.step_delta.y;
+        }
+
+        Some(cur)
+    }
+}