//With thanks to following:
//http://ogldev.atspace.co.uk/www/tutorial19/tutorial19.html
private Colour CalculateSpecularColour(ILight lightSource, Vector3 cameraLocation, Vector3 hitLoc, IShape shape)
{
Colour specColour = new Colour(0, 0, 0);
Vector3 i = Vector3.Normalize(lightSource.GetOrigin() - hitLoc); //LightVector
Vector3 normal = Vector3.Normalize(shape.GetOrigin() - hitLoc);
Vector3 v = Vector3.Normalize(hitLoc - cameraLocation); //Vector to Eye
Vector3 r = Vector3.Normalize(Vector3.Reflect(i, normal));
float specFactor = Vector3.Dot(v, r);
if (specFactor > 0.0f)
{
specFactor = (float)Math.Pow(specFactor, spec_power);
specColour = lightSource.GetColour() * spec_intensity * specFactor;
}
return(specColour);
}