Thread: What is what in a 4*4 matrix

In short the 4x4 matrix is used to combine transformation and translation matrices together. Otherwise you would have screwed up equations trying to combine transformations (such as a rotation or scale) with a translation.

the first 3x3 portion is the transformation matrix
the fourth column is the three dimensional translation (displacement vector) matrix. The fourth row is comprised of zeros except for the last element of the matrix which is 1 when dealing with a point and 0 when dealing with a vector

assume x = transformation matrix
t = translation matrix
[x x x t]
[x x x t]
[x x x t]
[0 0 0 w]
w = 1 if operating on a point
w = 0 if operating on a vector

EDIT: this is pretty complex stuff just so you know. If you are just starting out I kinda doubt you're really going to need to know 100% of what I just told you. I haven't even delved into this extensively on my own, I just know what I'm talking about in 'vague' terms, I haven't actually used this into any programs.