   Directional Diffuse Light Source in Eye Cordinates
  Hey!I have a class which requires me to write a graphical engine in some obscure, forgotten programming language.I've gotten quite far, everything works fine... except light comming from an infinite diffusion source.Given are some figures I have to render (like a cube or a sphere) which have some reflection to some kind of light, the camera view-point and the light sources.Now, I have the feeling I need to convert my light 'direction' into my eye coordinates... Just multiplying it with the matrix used for the perspective transformation isn't going to work, because my light source isn't a point.What operations do I have to do on my direction vector (x,y,z) given theta, phi & rho being the polar coordinates of my viewpoint?It's possible I have some flaws in my reasoning... I've been debugging for two days straight now, and can't seem to work it out ...Thanks in advance!   
  If you're just asking how to transform a vector (rather than a point) by a transformation matrix, that's fairly straightforward. Assuming you have a 4x4 matrix representing your view transform, the standard method would be to represent the vector as the 4-d homogenous vector (x, y, z, 0), and multiply this vector by the view matrix. Then, just drop the 'w' element of the result to yield the transformed direction vector.   