diff --git a/src/aabb.rs b/src/aabb.rs
index 5cb8620..b0d1846 100644
--- a/src/aabb.rs
+++ b/src/aabb.rs
@@ -20,11 +20,13 @@
 //! dimension) where the slope of every line is either 0 or undefined. These
 //! are useful for very cheap collision detection.
 
+use bound::*;
 use point::{Point, Point2, Point3};
 use vector::{Vector, Vector2, Vector3};
 use ray::{Ray2};
 use intersect::Intersect;
 use num::{zero, one, BaseNum, BaseFloat};
+use plane::Plane;
 use std::fmt;
 use std::num::Float;
 
@@ -101,6 +103,15 @@ impl<S: BaseNum> Aabb2<S> {
                              p1.y.partial_max(p2.y)),
         }
     }
+
+    /// Compute corners.
+    #[inline]
+    pub fn to_corners(&self) -> [Point2<S>; 4] {
+        [self.min,
+        Point2::new(self.max.x, self.min.y),
+        Point2::new(self.min.x, self.max.y),
+        self.max]
+    }
 }
 
 impl<S: BaseNum> Aabb<S, Vector2<S>, Point2<S>> for Aabb2<S> {
@@ -148,6 +159,19 @@ impl<S: BaseNum> Aabb3<S> {
                              p1.z.partial_max(p2.z)),
         }
     }
+
+    /// Compute corners.
+    #[inline]
+    pub fn to_corners(&self) -> [Point3<S>; 8] {
+        [self.min,
+        Point3::new(self.max.x, self.min.y, self.min.z),
+        Point3::new(self.min.x, self.max.y, self.min.z),
+        Point3::new(self.max.x, self.max.y, self.min.z),
+        Point3::new(self.min.x, self.min.y, self.max.z),
+        Point3::new(self.max.x, self.min.y, self.max.z),
+        Point3::new(self.min.x, self.max.y, self.max.z),
+        self.max]
+    }
 }
 
 impl<S: BaseNum> Aabb<S, Vector3<S>, Point3<S>> for Aabb3<S> {
@@ -217,3 +241,16 @@ impl<S: BaseFloat> Intersect<Option<Point2<S>>> for (Ray2<S>, Aabb2<S>) {
         }
     }
 }
+
+impl<S: BaseFloat + 'static> Bound<S> for Aabb3<S> {
+    fn relate_plane(&self, plane: &Plane<S>) -> Relation {
+        let corners = self.to_corners();
+        let first = corners[0].relate_plane(plane);
+        for p in corners[1..].iter() {
+            if p.relate_plane(plane) != first {
+                return Relation::Cross;
+            }
+        }
+        first
+    }
+}
diff --git a/src/bound.rs b/src/bound.rs
new file mode 100644
index 0000000..4154ebf
--- /dev/null
+++ b/src/bound.rs
@@ -0,0 +1,46 @@
+// Copyright 2013-2014 The CGMath Developers. For a full listing of the authors,
+// refer to the AUTHORS file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Generic spatial bounds.
+
+use matrix::Matrix4;
+use num::BaseFloat;
+use plane::Plane;
+
+/// Spatial relation between two objects.
+#[derive(Copy, Clone, Debug, Eq, Hash, Ord, PartialOrd, PartialEq)]
+#[repr(u8)]
+pub enum Relation {
+    /// Completely inside.
+    In,
+    /// Crosses the boundary.
+    Cross,
+    /// Completely outside.
+    Out,
+}
+
+/// Generic bound.
+pub trait Bound<S: BaseFloat + 'static>: Sized {
+    /// Classify the spatial relation with a plane.
+    fn relate_plane(&self, &Plane<S>) -> Relation;
+    /// Classify the relation with a projection matrix.
+    fn relate_clip_space(&self, projection: &Matrix4<S>) -> Relation {
+        use frustum::Frustum;
+        match Frustum::from_matrix4(*projection) {
+            Some(f) => f.contains(self),
+            None => Relation::Cross,
+        }
+    }
+}
diff --git a/src/frustum.rs b/src/frustum.rs
index 579bb1d..e9e4468 100644
--- a/src/frustum.rs
+++ b/src/frustum.rs
@@ -16,14 +16,15 @@
 //! View frustum for visibility determination
 
 use array::Array2;
+use bound::*;
 use matrix::Matrix4;
 use num::BaseFloat;
 use plane::Plane;
 use point::Point3;
 use vector::{Vector, EuclideanVector};
 
-#[derive(Copy, Clone, PartialEq, RustcEncodable, RustcDecodable)]
-pub struct Frustum<S> {
+#[derive(Copy, Clone, Debug, PartialEq, RustcEncodable, RustcDecodable)]
+pub struct Frustum<S: BaseFloat> {
     pub left:   Plane<S>,
     pub right:  Plane<S>,
     pub bottom: Plane<S>,
@@ -34,7 +35,7 @@ pub struct Frustum<S> {
 
 impl<S: BaseFloat + 'static>
 Frustum<S> {
-    /// Constructs a frustum
+    /// Construct a frustum.
     pub fn new(left:   Plane<S>, right:  Plane<S>,
                bottom: Plane<S>, top:    Plane<S>,
                near:   Plane<S>, far:    Plane<S>) -> Frustum<S> {
@@ -48,14 +49,35 @@ Frustum<S> {
         }
     }
 
-    /// Extracts frustum planes from a projection matrix
-    pub fn from_matrix4(mat: Matrix4<S>) -> Frustum<S> {
-        Frustum::new(Plane::from_vector4(mat.row(3).add_v(&mat.row(0)).normalize()),
-                     Plane::from_vector4(mat.row(3).sub_v(&mat.row(0)).normalize()),
-                     Plane::from_vector4(mat.row(3).add_v(&mat.row(1)).normalize()),
-                     Plane::from_vector4(mat.row(3).sub_v(&mat.row(1)).normalize()),
-                     Plane::from_vector4(mat.row(3).add_v(&mat.row(2)).normalize()),
-                     Plane::from_vector4(mat.row(3).sub_v(&mat.row(2)).normalize()))
+    /// Extract frustum planes from a projection matrix.
+    pub fn from_matrix4(mat: Matrix4<S>) -> Option<Frustum<S>> {
+        Some(Frustum::new(
+            match Plane::from_vector4_alt(mat.row(3).add_v(&mat.row(0))).normalize()
+                { Some(p) => p, None => return None },
+            match Plane::from_vector4_alt(mat.row(3).sub_v(&mat.row(0))).normalize()
+                { Some(p) => p, None => return None },
+            match Plane::from_vector4_alt(mat.row(3).add_v(&mat.row(1))).normalize()
+                { Some(p) => p, None => return None },
+            match Plane::from_vector4_alt(mat.row(3).sub_v(&mat.row(1))).normalize()
+                { Some(p) => p, None => return None },
+            match Plane::from_vector4_alt(mat.row(3).add_v(&mat.row(2))).normalize()
+                { Some(p) => p, None => return None },
+            match Plane::from_vector4_alt(mat.row(3).sub_v(&mat.row(2))).normalize()
+                { Some(p) => p, None => return None }
+        ))
+    }
+
+    /// Find the spatial relation of a bound inside this frustum.
+    pub fn contains<B: Bound<S>>(&self, bound: &B) -> Relation {
+        [&self.left, &self.right, &self.top, &self.bottom, &self.near, &self.far]
+            .iter().fold(Relation::In, |cur, p| {
+            use std::cmp::max;
+            let r = bound.relate_plane(p);
+            // If any of the planes are `Out`, the bound is outside.
+            // Otherwise, if any are `Cross`, the bound is crossing.
+            // Otherwise, the bound is fully inside.
+            max(cur, r)
+        })
     }
 }
 
diff --git a/src/cgmath.rs b/src/lib.rs
similarity index 98%
rename from src/cgmath.rs
rename to src/lib.rs
index c8335da..f1eb8ef 100644
--- a/src/cgmath.rs
+++ b/src/lib.rs
@@ -52,6 +52,7 @@ pub use transform::*;
 pub use projection::*;
 
 pub use aabb::*;
+pub use bound::*;
 pub use cylinder::Cylinder;
 pub use frustum::{Frustum, FrustumPoints};
 pub use intersect::Intersect;
@@ -80,6 +81,7 @@ mod transform;
 mod projection;
 
 mod aabb;
+mod bound;
 mod cylinder;
 mod frustum;
 mod intersect;
diff --git a/src/plane.rs b/src/plane.rs
index ada76f4..909045e 100644
--- a/src/plane.rs
+++ b/src/plane.rs
@@ -17,7 +17,7 @@ use std::fmt;
 
 use approx::ApproxEq;
 use intersect::Intersect;
-use num::{BaseFloat, Zero, zero};
+use num::{BaseFloat, one, Zero, zero};
 use point::{Point, Point3};
 use ray::Ray3;
 use vector::{Vector3, Vector4};
@@ -65,9 +65,13 @@ impl<S: BaseFloat> Plane<S> {
 
     /// Construct a plane from the components of a four-dimensional vector
     pub fn from_vector4(v: Vector4<S>) -> Plane<S> {
-        match v {
-            Vector4 { x, y, z, w } => Plane { n: Vector3::new(x, y, z), d: w },
-        }
+        Plane { n: Vector3::new(v.x, v.y, v.z), d: v.w }
+    }
+
+    /// Construct a plane from the components of a four-dimensional vector
+    /// Assuming alternative representation: `A*x + B*y + C*z + D = 0`
+    pub fn from_vector4_alt(v: Vector4<S>) -> Plane<S> {
+        Plane { n: Vector3::new(v.x, v.y, v.z), d: -v.w }
     }
 
     /// Constructs a plane that passes through the the three points `a`, `b` and `c`
@@ -94,6 +98,15 @@ impl<S: BaseFloat> Plane<S> {
     pub fn from_point_normal(p: Point3<S>, n: Vector3<S>) -> Plane<S> {
         Plane { n: n, d: p.dot(&n) }
     }
+
+    /// Normalize a plane.
+    pub fn normalize(&self) -> Option<Plane<S>> {
+        if self.n.approx_eq(&zero()) { None }
+        else {
+            let denom = one::<S>() / self.n.length();
+            Some(Plane::new(self.n.mul_s(denom), self.d*denom))
+        }
+    }
 }
 
 impl<S: BaseFloat> Intersect<Option<Point3<S>>> for (Plane<S>, Ray3<S>) {
diff --git a/src/point.rs b/src/point.rs
index 4b8d6e3..ab854dd 100644
--- a/src/point.rs
+++ b/src/point.rs
@@ -23,7 +23,10 @@ use std::ops::*;
 
 use approx::ApproxEq;
 use array::{Array1, FixedArray};
+use bound::*;
+use matrix::{Matrix, Matrix4};
 use num::{BaseNum, BaseFloat, one, zero};
+use plane::Plane;
 use vector::*;
 
 /// A point in 2-dimensional space.
@@ -445,3 +448,26 @@ impl<S: BaseNum> fmt::Debug for Point3<S> {
         write!(f, "[{:?}, {:?}, {:?}]", self.x, self.y, self.z)
     }
 }
+
+impl<S: BaseFloat + 'static> Bound<S> for Point3<S> {
+    fn relate_plane(&self, plane: &Plane<S>) -> Relation {
+        let dist = self.dot(&plane.n);
+        if dist > plane.d {
+            Relation::In
+        }else if dist < plane.d {
+            Relation::Out
+        }else {
+            Relation::Cross
+        }
+    }
+
+    fn relate_clip_space(&self, projection: &Matrix4<S>) -> Relation {
+        use std::cmp::Ordering::*;
+        let p = projection.mul_v(&self.to_homogeneous());
+        match (p.x.abs().partial_cmp(&p.w), p.y.abs().partial_cmp(&p.w), p.z.abs().partial_cmp(&p.w)) {
+            (Some(Less), Some(Less), Some(Less)) => Relation::In,
+            (Some(Greater), _, _) | (_, Some(Greater), _) | (_, _, Some(Greater)) => Relation::Out,
+            _ => Relation::Cross,
+        }
+    }
+}
diff --git a/src/projection.rs b/src/projection.rs
index 7dc9753..733197c 100644
--- a/src/projection.rs
+++ b/src/projection.rs
@@ -97,7 +97,7 @@ impl<S: BaseFloat, A: Angle<S>> PerspectiveFov<S, A> {
 impl<S: BaseFloat + 'static, A: Angle<S>> Projection<S> for PerspectiveFov<S, A> {
     fn to_frustum(&self) -> Frustum<S> {
         // TODO: Could this be faster?
-        Frustum::from_matrix4(self.to_matrix4())
+        Frustum::from_matrix4(self.to_matrix4()).unwrap()
     }
 }
 
@@ -153,7 +153,7 @@ pub struct Perspective<S> {
 impl<S: BaseFloat + 'static> Projection<S> for Perspective<S> {
     fn to_frustum(&self) -> Frustum<S> {
         // TODO: Could this be faster?
-        Frustum::from_matrix4(self.to_matrix4())
+        Frustum::from_matrix4(self.to_matrix4()).unwrap()
     }
 }
 
diff --git a/src/sphere.rs b/src/sphere.rs
index 46474e9..61565ac 100644
--- a/src/sphere.rs
+++ b/src/sphere.rs
@@ -15,9 +15,11 @@
 
 //! Bounding sphere
 
+use bound::*;
 use intersect::Intersect;
 use num::{BaseFloat, zero};
 use point::{Point, Point3};
+use plane::Plane;
 use ray::Ray3;
 use vector::Vector;
 
@@ -42,3 +44,16 @@ impl<S: BaseFloat> Intersect<Option<Point3<S>>> for (Sphere<S>, Ray3<S>) {
         }
     }
 }
+
+impl<S: BaseFloat + 'static> Bound<S> for Sphere<S> {
+    fn relate_plane(&self, plane: &Plane<S>) -> Relation {
+        let dist = self.center.dot(&plane.n) - plane.d;
+        if dist > self.radius {
+            Relation::In
+        }else if dist < - self.radius {
+            Relation::Out
+        }else {
+            Relation::Cross
+        }
+    }
+}
diff --git a/tests/aabb.rs b/tests/aabb.rs
index 3bc0870..41cf0db 100644
--- a/tests/aabb.rs
+++ b/tests/aabb.rs
@@ -19,53 +19,54 @@ use cgmath::{Aabb, Aabb2, Aabb3};
 use cgmath::{Point2, Point3};
 use cgmath::{Vector2, Vector3};
 use cgmath::{Ray, Intersect};
+use cgmath::{Plane, Bound, Relation};
 
 #[test]
-fn test_aabb() {
-    let aabb = Aabb2::new(Point2::new(-20is, 30is), Point2::new(10is, -10is));
-    assert_eq!(aabb.min(), &Point2::new(-20is, -10is));
-    assert_eq!(aabb.max(), &Point2::new(10is, 30is));
-    assert_eq!(aabb.dim(), Vector2::new(30is, 40is));
-    assert_eq!(aabb.volume(), 30is * 40is);
-    assert_eq!(aabb.center(), Point2::new(-5is, 10is));
+fn test_general() {
+    let aabb = Aabb2::new(Point2::new(-20isize, 30isize), Point2::new(10isize, -10isize));
+    assert_eq!(aabb.min(), &Point2::new(-20isize, -10isize));
+    assert_eq!(aabb.max(), &Point2::new(10isize, 30isize));
+    assert_eq!(aabb.dim(), Vector2::new(30isize, 40isize));
+    assert_eq!(aabb.volume(), 30isize * 40isize);
+    assert_eq!(aabb.center(), Point2::new(-5isize, 10isize));
 
-    assert!(aabb.contains(&Point2::new(0is, 0is)));
-    assert!(!aabb.contains(&Point2::new(-50is, -50is)));
-    assert!(!aabb.contains(&Point2::new(50is, 50is)));
+    assert!(aabb.contains(&Point2::new(0isize, 0isize)));
+    assert!(!aabb.contains(&Point2::new(-50isize, -50isize)));
+    assert!(!aabb.contains(&Point2::new(50isize, 50isize)));
 
-    assert_eq!(aabb.grow(&Point2::new(0is, 0is)), aabb);
-    assert_eq!(aabb.grow(&Point2::new(100is, 100is)),
-        Aabb2::new(Point2::new(-20is, -10is), Point2::new(100is, 100is)));
-    assert_eq!(aabb.grow(&Point2::new(-100is, -100is)),
-        Aabb2::new(Point2::new(-100is, -100is), Point2::new(10is, 30is)));
+    assert_eq!(aabb.grow(&Point2::new(0isize, 0isize)), aabb);
+    assert_eq!(aabb.grow(&Point2::new(100isize, 100isize)),
+        Aabb2::new(Point2::new(-20isize, -10isize), Point2::new(100isize, 100isize)));
+    assert_eq!(aabb.grow(&Point2::new(-100isize, -100isize)),
+        Aabb2::new(Point2::new(-100isize, -100isize), Point2::new(10isize, 30isize)));
 
-    let aabb = Aabb3::new(Point3::new(-20is, 30is, 5is), Point3::new(10is, -10is, -5is));
-    assert_eq!(aabb.min(), &Point3::new(-20is, -10is, -5is));
-    assert_eq!(aabb.max(), &Point3::new(10is, 30is, 5is));
-    assert_eq!(aabb.dim(), Vector3::new(30is, 40is, 10is));
-    assert_eq!(aabb.volume(), 30is * 40is * 10is);
-    assert_eq!(aabb.center(), Point3::new(-5is, 10is, 0is));
+    let aabb = Aabb3::new(Point3::new(-20isize, 30isize, 5isize), Point3::new(10isize, -10isize, -5isize));
+    assert_eq!(aabb.min(), &Point3::new(-20isize, -10isize, -5isize));
+    assert_eq!(aabb.max(), &Point3::new(10isize, 30isize, 5isize));
+    assert_eq!(aabb.dim(), Vector3::new(30isize, 40isize, 10isize));
+    assert_eq!(aabb.volume(), 30isize * 40isize * 10isize);
+    assert_eq!(aabb.center(), Point3::new(-5isize, 10isize, 0isize));
 
-    assert!(aabb.contains(&Point3::new(0is, 0is, 0is)));
-    assert!(!aabb.contains(&Point3::new(-100is, 0is, 0is)));
-    assert!(!aabb.contains(&Point3::new(100is, 0is, 0is)));
-    assert!(aabb.contains(&Point3::new(9is, 29is, -1is)));
-    assert!(!aabb.contains(&Point3::new(10is, 30is, 5is)));
-    assert!(aabb.contains(&Point3::new(-20is, -10is, -5is)));
-    assert!(!aabb.contains(&Point3::new(-21is, -11is, -6is)));
+    assert!(aabb.contains(&Point3::new(0isize, 0isize, 0isize)));
+    assert!(!aabb.contains(&Point3::new(-100isize, 0isize, 0isize)));
+    assert!(!aabb.contains(&Point3::new(100isize, 0isize, 0isize)));
+    assert!(aabb.contains(&Point3::new(9isize, 29isize, -1isize)));
+    assert!(!aabb.contains(&Point3::new(10isize, 30isize, 5isize)));
+    assert!(aabb.contains(&Point3::new(-20isize, -10isize, -5isize)));
+    assert!(!aabb.contains(&Point3::new(-21isize, -11isize, -6isize)));
 
-    assert_eq!(aabb.add_v(&Vector3::new(1is, 2is, 3is)),
-        Aabb3::new(Point3::new(-19is, 32is, 8is), Point3::new(11is, -8is, -2is)));
+    assert_eq!(aabb.add_v(&Vector3::new(1isize, 2isize, 3isize)),
+        Aabb3::new(Point3::new(-19isize, 32isize, 8isize), Point3::new(11isize, -8isize, -2isize)));
 
-    assert_eq!(aabb.mul_s(2is),
-        Aabb3::new(Point3::new(-40is, -20is, -10is), Point3::new(20is, 60is, 10is)));
+    assert_eq!(aabb.mul_s(2isize),
+        Aabb3::new(Point3::new(-40isize, -20isize, -10isize), Point3::new(20isize, 60isize, 10isize)));
 
-    assert_eq!(aabb.mul_v(&Vector3::new(1is, 2is, 3is)),
-        Aabb3::new(Point3::new(-20is, -20is, -15is), Point3::new(10is, 60is, 15is)));
+    assert_eq!(aabb.mul_v(&Vector3::new(1isize, 2isize, 3isize)),
+        Aabb3::new(Point3::new(-20isize, -20isize, -15isize), Point3::new(10isize, 60isize, 15isize)));
 }
 
 #[test]
-fn test_aabb_ray_intersect() {
+fn test_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));
@@ -77,3 +78,28 @@ fn test_aabb_ray_intersect() {
     assert_eq!((ray3, aabb).intersection(), None);
     assert_eq!((ray4, aabb).intersection(), Some(Point2::new(5.0, 9.0)));
 }
+
+#[test]
+fn test_corners() {
+    let corners = Aabb2::new(Point2::new(-5.0f32, 5.0), Point2::new(5.0, 10.0))
+                        .to_corners();
+    assert!(corners.contains(&Point2::new(-5f32, 10.0)));
+    assert!(corners.contains(&Point2::new(5f32, 5.0)));
+
+    let corners = Aabb3::new(Point3::new(-20isize, 30isize, 5isize), Point3::new(10isize, -10isize, -5isize))
+                        .to_corners();
+    assert!(corners.contains(&Point3::new(-20isize, 30isize, -5isize)));
+    assert!(corners.contains(&Point3::new(10isize, 30isize, 5isize)));
+    assert!(corners.contains(&Point3::new(10isize, -10isize, 5isize)));
+}
+
+#[test]
+fn test_bound() {
+    let aabb = Aabb3::new(Point3::new(-5.0f32, 5.0, 0.0), Point3::new(5.0, 10.0, 1.0));
+    let plane1 = Plane::from_point_normal(Point3::new(0f32, 0.0, 0.0), Vector3::new(0f32, 0.0, 1.0));
+    let plane2 = Plane::from_point_normal(Point3::new(-5.0f32, 4.0, 0.0), Vector3::new(0f32, 1.0, 0.0));
+    let plane3 = Plane::from_point_normal(Point3::new(6.0f32, 0.0, 0.0), Vector3::new(1f32, 0.0, 0.0));
+    assert_eq!(aabb.relate_plane(&plane1), Relation::Cross);
+    assert_eq!(aabb.relate_plane(&plane2), Relation::In);
+    assert_eq!(aabb.relate_plane(&plane3), Relation::Out);
+}
diff --git a/tests/frustum.rs b/tests/frustum.rs
new file mode 100644
index 0000000..ba2a9e7
--- /dev/null
+++ b/tests/frustum.rs
@@ -0,0 +1,40 @@
+// Copyright 2015 The CGMath Developers. For a full listing of the authors,
+// refer to the AUTHORS file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+extern crate cgmath;
+
+use cgmath::{PerspectiveFov, Point3, Projection, Relation, Sphere, rad};
+
+#[test]
+fn test_contains() {
+    let frustum = PerspectiveFov {
+        fovy: rad(1f32),
+        aspect: 1f32,
+        near: 1f32,
+        far: 10f32,
+    }.to_frustum();
+    assert_eq!(frustum.contains(&Sphere {
+            center: Point3::new(0f32, 0f32, -5f32),
+            radius: 1f32,
+        }), Relation::In);
+    assert_eq!(frustum.contains(&Sphere {
+            center: Point3::new(0f32, 3f32, -5f32),
+            radius: 1f32,
+        }), Relation::Cross);
+    assert_eq!(frustum.contains(&Sphere {
+            center: Point3::new(0f32, 0f32, 5f32),
+            radius: 1f32,
+        }), Relation::Out);
+}
diff --git a/tests/point.rs b/tests/point.rs
index 93f8047..5f65f3c 100644
--- a/tests/point.rs
+++ b/tests/point.rs
@@ -16,11 +16,23 @@
 
 extern crate cgmath;
 
-use cgmath::Point3;
-use cgmath::ApproxEq;
+use cgmath::{Point, Point3, Vector, Vector3};
+use cgmath::{Bound, Relation, Plane};
+use cgmath::{ApproxEq};
 
 #[test]
 fn test_homogeneous() {
 	let p = Point3::new(1.0f64, 2.0f64, 3.0f64);
     assert!(p.approx_eq( &Point3::from_homogeneous( &p.to_homogeneous() ) ));
 }
+
+#[test]
+fn test_bound() {
+    let point = Point3::new(1f32, 2.0, 3.0);
+    let normal = Vector3::new(0f32, -0.8, -0.36);
+    let plane = Plane::from_point_normal(point, normal);
+
+    assert_eq!(point.relate_plane(&plane), Relation::Cross);
+    assert_eq!(point.add_v(&normal).relate_plane(&plane), Relation::In);
+    assert_eq!(point.add_v(&normal.mul_s(-1.0)).relate_plane(&plane), Relation::Out);
+}
diff --git a/tests/sphere.rs b/tests/sphere.rs
index b54ab83..a3f61eb 100644
--- a/tests/sphere.rs
+++ b/tests/sphere.rs
@@ -31,3 +31,20 @@ fn test_intersection() {
     assert_eq!((sphere,r2).intersection(), Some(Point3::new(1f64, 0f64, 0f64)));
     assert_eq!((sphere,r3).intersection(), None);
 }
+
+#[test]
+fn test_bound() {
+    let point = Point3::new(1f32, 2.0, 3.0);
+    let sphere = Sphere { center: point, radius: 1.0 };
+    let normal = vec3(0f32, 0.0, 1.0);
+
+    assert_eq!(sphere.relate_plane(
+        &Plane::from_point_normal(point, normal)
+        ), Relation::Cross);
+    assert_eq!(sphere.relate_plane(
+        &Plane::from_point_normal(point.add_v(&normal.mul_s(-3.0)), normal),
+        ), Relation::In);
+    assert_eq!(sphere.relate_plane(
+        &Plane::from_point_normal(point.add_v(&normal.mul_s(3.0)), normal),
+        ), Relation::Out);
+}