rtiow: AABB handle infinite bounds better.

rtiow/renderer/src/aabb.rs

@@ -47,7 +47,7 @@ impl AABB {
     // a vaild AABB.
     pub fn infinite() -> AABB {
         AABB {
-            bounds: [Vec3::from(f32::MAX), -Vec3::from(f32::MAX)],
+            bounds: [Vec3::from(f32::MAX), Vec3::from(f32::MIN)],
         }
     }
     pub fn new<V: Into<Vec3>>(min: V, max: V) -> AABB {
@@ -60,13 +60,29 @@ impl AABB {
     }
 
     pub fn area(&self) -> f32 {
+        if self.max().x == f32::MIN || self.min().x == f32::MAX {
+            return 0.;
+        }
         let e = self.max() - self.min();
-        e.x * e.y + e.y * e.z + e.z * e.x
+        let v = e.x * e.y + e.y * e.z + e.z * e.x;
+        if v.is_finite() {
+            v
+        } else {
+            0.
+        }
     }
     pub fn volume(&self) -> f32 {
-        (self.min().x - self.max().x).abs()
+        if self.max().x == f32::MIN || self.min().x == f32::MAX {
+            return 0.;
+        }
+        let v = (self.min().x - self.max().x).abs()
             * (self.min().y - self.max().y).abs()
-            * (self.min().z - self.max().z).abs()
+            * (self.min().z - self.max().z).abs();
+        if v.is_finite() {
+            v
+        } else {
+            0.
+        }
     }
 
     pub fn grow(&mut self, v: Vec3) {
@@ -255,6 +271,13 @@ pub fn surrounding_box(box0: &AABB, box1: &AABB) -> AABB {
 mod tests {
     use super::*;
 
+    #[test]
+    fn infinite() {
+        let bb = AABB::infinite();
+        assert_eq!(bb.area(), 0.);
+        assert_eq!(bb.volume(), 0.);
+    }
+
     macro_rules! hit_test {
         ($($name:ident,)*) => {
             $(