Something with raytracing that has gone wrong

Question

I'm trying to do a simple ray tracing assignment, in c# (ported from python). I've managed to make the sample code show the correct picture, but when I try and adapt it to my assignment something goes wrong.

If I knew what was going wrong I would post some code that I thought might help, but I have no idea where to start.

Basically my assignment outputs something like this:

http://i56.tinypic.com/2vcdobq.png

With specular highlighting on, and

http://i53.tinypic.com/2e1r38o.png

With it off. It's suppose to look something like:

http://i56.tinypic.com/2m7sxlh.png

My Phong lighting formula looks like:

Colour I = diffuse_colour;
Vector L = light.vector;
Vector N = normal; //FIXME!
Colour Is = diffuse_colour * light.intensity;
Colour Ia = new Colour(1,1,1) * light.ambient;
Colour Kd = specular_colour;
Colour Ka = Kd;
double Ks = sharpness ?? 0.4;
Vector H = Vector.unit(view + L);

//Phong Illumination
//I = KaIa + KdIs max(0,L.N) + KsIs (H.N)^n

I = Ka * Ia
+ Kd * Is * Math.Max(0, L.dot(N))
+ Ks * Is * Math.Pow(H.dot(N),200); //FIXME?

And I copied it from the working sample code, so I know it works.

Any thoughts would be great, because I'm stumped.

Answer 1

You have two implementations of the same algorithm. You claim that they produce different results. Finding the mistake seems straightforward: run both algorithms step by step in their respective debuggers, simultaneously. Watch the state of both programs carefully. The moment they produce different program states, there's your bug.