diff --git a/rtiow/renderer/src/aabb.rs b/rtiow/renderer/src/aabb.rs
index 9936da3..2ffa4ce 100644
--- a/rtiow/renderer/src/aabb.rs
+++ b/rtiow/renderer/src/aabb.rs
@@ -42,6 +42,13 @@ impl fmt::Debug for AABB {
 }
 
 impl AABB {
+    // Create AABB with min = f32::MAX and max = -f32::MAX. It is expected the caller will use grow to create
+    // a vaild AABB.
+    pub fn infinite() -> AABB {
+        AABB {
+            bounds: [Vec3::from(f32::MAX), -Vec3::from(f32::MAX)],
+        }
+    }
     pub fn new<V: Into<Vec3>>(min: V, max: V) -> AABB {
         let min: Vec3 = min.into();
         let max: Vec3 = max.into();
@@ -51,12 +58,21 @@ impl AABB {
         AABB { bounds: [min, max] }
     }
 
+    pub fn area(&self) -> f32 {
+        let e = self.max() - self.min();
+        e.x * e.y + e.y * e.z + e.z * e.x
+    }
     pub fn volume(&self) -> f32 {
         (self.min().x - self.max().x).abs()
             * (self.min().y - self.max().y).abs()
             * (self.min().z - self.max().z).abs()
     }
 
+    pub fn grow(&mut self, v: Vec3) {
+        self.bounds[0] = vec3::min(self.bounds[0], v);
+        self.bounds[1] = vec3::max(self.bounds[1], v);
+    }
+
     pub fn longest_axis(&self) -> usize {
         let xd = (self.min().x - self.max().x).abs();
         let yd = (self.min().y - self.max().y).abs();