Add Ray2<>Aabb2 intersection impl

src/aabb.rs

@@ -22,9 +22,11 @@
 
 use point::{Point, Point2, Point3};
 use vector::{Vector, Vector2, Vector3};
-use num::BaseNum;
+use ray::{Ray2};
+use intersect::Intersect;
+use num::{BaseNum, BaseFloat};
 use std::fmt;
-use std::num::{zero, one};
+use std::num::{zero, one, Float};
 
 pub trait Aabb<S: BaseNum, V: Vector<S>, P: Point<S, V>> {
     /// Create a new AABB using two points as opposing corners.
@@ -172,3 +174,46 @@ impl<S: BaseNum> fmt::Show for Aabb3<S> {
         write!(f, "[{} - {}]", self.min, self.max)
     }
 }
+
+impl<S: BaseFloat> Intersect<Option<Point2<S>>> for (Ray2<S>, Aabb2<S>) {
+    fn intersection(&self) -> Option<Point2<S>> {
+        match *self {
+            (ref ray, ref aabb) => {
+
+                let mut tmin: S = Float::neg_infinity();
+                let mut tmax: S = Float::infinity();
+
+                if ray.direction.x != zero() {
+                    let tx1 = (aabb.min.x - ray.origin.x) / ray.direction.x;
+                    let tx2 = (aabb.max.x - ray.origin.x) / ray.direction.x;
+                    tmin = tmin.max(tx1.min(tx2));
+                    tmax = tmax.min(tx1.max(tx2));
+                }
+
+                if ray.direction.y != zero() {
+                    let ty1 = (aabb.min.y - ray.origin.y) / ray.direction.y;
+                    let ty2 = (aabb.max.y - ray.origin.y) / ray.direction.y;
+                    tmin = tmin.max(ty1.min(ty2));
+                    tmax = tmax.min(ty1.max(ty2));
+                }
+
+                if tmin < zero() && tmax < zero() {
+                    None
+                }
+                else if tmax >= tmin {
+                    if tmin >= zero() {
+                        Some(Point2::new(ray.origin.x + ray.direction.x * tmin,
+                                         ray.origin.y + ray.direction.y * tmin))
+                    }
+                    else {
+                        Some(Point2::new(ray.origin.x + ray.direction.x * tmax,
+                                         ray.origin.y + ray.direction.y * tmax))
+                    }
+                }
+                else {
+                    None
+                }
+            }
+        }
+    }
+}

tests/aabb.rs

@@ -20,6 +20,8 @@ extern crate cgmath;
 use cgmath::aabb::*;
 use cgmath::point::{Point2, Point3};
 use cgmath::vector::{Vector2, Vector3};
+use cgmath::ray::{Ray};
+use cgmath::intersect::Intersect;
 
 #[test]
 fn test_aabb() {
@@ -64,3 +66,17 @@ fn test_aabb() {
     assert_eq!(aabb.mul_v(&Vector3::new(1i, 2i, 3i)),
         Aabb3::new(Point3::new(-20i, -20i, -15i), Point3::new(10i, 60i, 15i)));
 }
+
+#[test]
+fn test_aabb_ray_intersect() {
+    let aabb = Aabb2::new(Point2::new(-5.0f32, 5.0), Point2::new(5.0, 10.0));
+    let ray1 = Ray::new(Point2::new(0.0f32, 0.0), Vector2::new(0.0, 1.0));
+    let ray2 = Ray::new(Point2::new(-10.0f32, 0.0), Vector2::new(2.5, 1.0));
+    let ray3 = Ray::new(Point2::new(0.0f32, 0.0), Vector2::new(-1.0, -1.0));
+    let ray4 = Ray::new(Point2::new(3.0f32, 7.0), Vector2::new(1.0, 1.0));
+
+    assert_eq!((ray1, aabb).intersection(), Some(Point2::new(0.0, 5.0)));
+    assert_eq!((ray2, aabb).intersection(), Some(Point2::new(2.5, 5.0)));
+    assert_eq!((ray3, aabb).intersection(), None);
+    assert_eq!((ray4, aabb).intersection(), Some(Point2::new(5.0, 9.0)));
+}