--- a/src/scene.h	Thu Nov 22 17:53:34 2007 +0100
+++ b/src/scene.h	Thu Nov 22 18:10:10 2007 +0100
@@ -94,7 +94,7 @@
 	// normal at point P
 	virtual Vector3 normal(Vector3 &P) = 0;
 
-	virtual BBox get_bbox();
+	virtual BBox get_bbox() = 0;
 };
 
 class Sphere: public Shape
@@ -111,6 +111,7 @@
 	bool intersect(const Ray &ray, float &dist);
 	bool intersect_all(const Ray &ray, float dist, vector<float> &allts);
 	Vector3 normal(Vector3 &P) { return (P - center) * inv_radius; };
+	BBox get_bbox();
 };
 
 class Plane: public Shape
@@ -126,6 +127,7 @@
 	bool intersect(const Ray &ray, float &dist);
 	bool intersect_all(const Ray &ray, float dist, vector<float> &allts) {return false;};
 	Vector3 normal(Vector3 &) { return N; };
+	BBox get_bbox();
 };
 
 class Triangle: public Shape