In computer graphics, one often sees the output of vertex shaders are 4-tuples. The first three numbers in the 4-tuple are x, y, and z coordinates. What is the 4th?
The homogeneous coordinate, sometimes referred to as the w coordinate. It serves 3 primary purposes. 1. Perspective Division --- objects farther away appear smaller (screen_x = x /w, etc.) 2. Matrix Multiplications --- the w coordinate allows for elegant handling of affine transformations via matrix multiplications. 3. Clipping and Depth Buffering --- helps determine whether an object is visible and its depth relative to other objects. TODO: sounds like a moron wrote this