avoid crashes on dir=0

src/camera.rs

@@ -20,6 +20,12 @@ impl OrbitalCamera {
 		self.distance * vec3(xy * x, xy * y, z)
 	}
 
+	pub fn direction(&self) -> Vec3 {
+		let (y, x) = self.position_yaw.sin_cos();
+		let (z, xy) = self.position_pitch.sin_cos();
+		-vec3(xy * x, xy * y, z)
+	}
+
 	pub fn transform(&self) -> Mat4 {
 		// for yaw=0, pitch=0:
 		// X -> -Z

src/lib.rs

@@ -393,7 +393,10 @@ impl Core {
 						.map(|&v| {
 							let pos = obj.position + obj.radius * v;
 							let normal = v;
-							let dir = (pos - camera.position()).normalize();
+							let mut dir = (pos - camera.position()).normalize();
+							if !dir.is_finite() {
+								dir = camera.direction();
+							}
 							let light = light_at(Hit {
 								incident: Ray::new(pos, dir),
 								normal,