Stage3D is hugely powerful, but with that power comes a very new and very complicated requirement for many programmers: shaders. Shaders are tiny programs that run on the GPU and are hugely limited compared to fancy CPU-side languages like AS3. For many programmers new to shaders these things are truly mind-bending. They’re even split into two parts: vertex and fragment shaders. Today’s article focuses on the two kinds of inputs to vertex shaders and seeks to explain them and clear up some of the confusion.