   transforming Vector 3 by a 4x4 matrix
  Hi i am trying to make a software renderer and i have got up to getting it into 3D, i have made a projection matrix but im not sure how i can transform the vector 3 by the matrix.I am doing it without using directx or anything like that so could anyone tell me how to do this or any site that might tell me?do i need to add a fourth element (x,y,z,w)? any help would be appreciated   
  How you transform the vector depends on what it represents. If it represents a point, like a vertex, you use a w coordinate of 1. If it represents a direction, like a normal, you use a w coordinate of 0.   ;  Ah thanks yea its to represent a point so i will use 1 for wanouther question after it has been transformed by the matrix how do i actually make it a vector 2 because it will still come out as a vector 3.Thanks   ;  Just ignore the z and w components.  Your 3D homogenous vector is now a simple 2D one.   