--- a/src/raytracer.cc	Thu Nov 22 17:53:34 2007 +0100
+++ b/src/raytracer.cc	Thu Nov 22 18:10:10 2007 +0100
@@ -230,7 +230,7 @@
 	vy = starty;
 
 #ifdef PTHREADS
-	int num_threads = 2;
+	int num_threads = 4;
 	printf("* pthreads enabled, using %d threads\n", num_threads);
 	pthread_t threads[num_threads];
 	for (int t = 0; t < num_threads; t++)

--- a/src/scene.cc	Thu Nov 22 17:53:34 2007 +0100
+++ b/src/scene.cc	Thu Nov 22 18:10:10 2007 +0100
@@ -71,6 +71,18 @@
 	return false;
 }
 
+BBox Sphere::get_bbox()
+{	
+	BBox bbox = BBox();
+	bbox.L.x = center.x - radius;
+	bbox.L.y = center.y - radius;
+	bbox.L.z = center.z - radius;
+	bbox.R.x = center.x + radius;
+	bbox.R.y = center.y + radius;
+	bbox.R.z = center.z + radius;
+	return bbox;
+}
+
 bool Plane::intersect(const Ray &ray, float &dist)
 {
 	float dir = dot(N, ray.dir);
@@ -85,6 +97,11 @@
 	return false;
 }
 
+BBox Plane::get_bbox()
+{	
+	return BBox();
+}
+
 // this initialization and following intersection methods implements
 // Fast Triangle Intersection algorithm from
 // http://www.mpi-inf.mpg.de/~wald/PhD/

--- 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