use nalgebra::na::{AlgebraicVecExt, Rotate, Transform, Identity, Cast};
use narrow::algorithm::johnson_simplex::JohnsonSimplex;
use bounding_volume::AABB;
use geom::{HasMargin, Box};
use ray::{Ray, RayCast, RayCastWithTransform};
use ray::ray_implicit::gjk_toi_and_normal_with_ray;

impl<N: Primitive + Orderable + Algebraic + Float + Cast<f32>,
     V: AlgebraicVecExt<N> + Clone>
RayCast<N, V> for Box<N, V> {
    #[inline]
    fn toi_with_ray(&self, ray: &Ray<V>) -> Option<N> {
        if self.margin().is_zero() {
            gjk_toi_and_normal_with_ray(
                &Identity::new(),
                self,
                &mut JohnsonSimplex::<N, V>::new_w_tls(),
                ray).map(|(n, _)| n)
        }
        else {
            AABB::new(-self.half_extents(), self.half_extents()).toi_with_ray(ray)
        }
    }

    #[inline]
    fn toi_and_normal_with_ray(&self, ray: &Ray<V>) -> Option<(N, V)> {
        if self.margin().is_zero() {
            AABB::new(-self.half_extents(), self.half_extents()).toi_and_normal_with_ray(ray)
        }
        else {
            gjk_toi_and_normal_with_ray(
                &Identity::new(),
                self,
                &mut JohnsonSimplex::<N, V>::new_w_tls(),
                ray)
        }
    }
}

impl<N: Primitive + Orderable + Algebraic + Float + Cast<f32>,
     V: AlgebraicVecExt<N> + Clone,
     M: Rotate<V> + Transform<V>>
RayCastWithTransform<N, V, M> for Box<N, V> { }

use nalgebra::na::{AlgebraicVecExt, Rotate, Transform};
use bounding_volume::AABB;
use geom::Box;
use ray::{Ray, RayCast, RayCastWithTransform};

impl<N: Primitive + Orderable + Algebraic,
     V: AlgebraicVecExt<N> + Clone>
RayCast<N, V> for Box<N, V> {
    #[inline]
    fn toi_with_ray(&self, ray: &Ray<V>) -> Option<N> {
        AABB::new(-self.half_extents(), self.half_extents()).toi_with_ray(ray)
    }

    #[inline]
    fn toi_and_normal_with_ray(&self, ray: &Ray<V>) -> Option<(N, V)> {
        AABB::new(-self.half_extents(), self.half_extents()).toi_and_normal_with_ray(ray)
    }
}

impl<N: Primitive + Orderable + Algebraic,
     V: AlgebraicVecExt<N> + Clone,
     M: Rotate<V> + Transform<V>>
RayCastWithTransform<N, V, M> for Box<N, V> { }

--- 
+++ 
@@ -1,23 +1,43 @@
-use nalgebra::na::{AlgebraicVecExt, Rotate, Transform};
+use nalgebra::na::{AlgebraicVecExt, Rotate, Transform, Identity, Cast};
+use narrow::algorithm::johnson_simplex::JohnsonSimplex;
 use bounding_volume::AABB;
-use geom::Box;
+use geom::{HasMargin, Box};
 use ray::{Ray, RayCast, RayCastWithTransform};
+use ray::ray_implicit::gjk_toi_and_normal_with_ray;
 
-impl<N: Primitive + Orderable + Algebraic,
+impl<N: Primitive + Orderable + Algebraic + Float + Cast<f32>,
      V: AlgebraicVecExt<N> + Clone>
 RayCast<N, V> for Box<N, V> {
     #[inline]
     fn toi_with_ray(&self, ray: &Ray<V>) -> Option<N> {
-        AABB::new(-self.half_extents(), self.half_extents()).toi_with_ray(ray)
+        if self.margin().is_zero() {
+            gjk_toi_and_normal_with_ray(
+                &Identity::new(),
+                self,
+                &mut JohnsonSimplex::<N, V>::new_w_tls(),
+                ray).map(|(n, _)| n)
+        }
+        else {
+            AABB::new(-self.half_extents(), self.half_extents()).toi_with_ray(ray)
+        }
     }
 
     #[inline]
     fn toi_and_normal_with_ray(&self, ray: &Ray<V>) -> Option<(N, V)> {
-        AABB::new(-self.half_extents(), self.half_extents()).toi_and_normal_with_ray(ray)
+        if self.margin().is_zero() {
+            AABB::new(-self.half_extents(), self.half_extents()).toi_and_normal_with_ray(ray)
+        }
+        else {
+            gjk_toi_and_normal_with_ray(
+                &Identity::new(),
+                self,
+                &mut JohnsonSimplex::<N, V>::new_w_tls(),
+                ray)
+        }
     }
 }
 
-impl<N: Primitive + Orderable + Algebraic,
+impl<N: Primitive + Orderable + Algebraic + Float + Cast<f32>,
      V: AlgebraicVecExt<N> + Clone,
      M: Rotate<V> + Transform<V>>
 RayCastWithTransform<N, V, M> for Box<N, V> { }
Use the gjk-based ray cast when a box geometry is not 0.
