charlequin said:I'm definitely not more qualified by any stretch of the imagination :lol but the short version is that vertex shaders are useful in creating deformation effects (cloth effects, certain animation effects, etc.) and "procedural geometry," and also are used in conjunction with pixel shaders to produce many advanced lighting effects, that is to say, they're super-important and not being able to do them sucks.
Vertex/geometry creation has only arrived latterly in the programmable pipeline. Or as part of geometry shaders....but traditionally you've not been able to create new vertices in vertex shaders. Procedural generation of geometry would happen on the CPU (or perhaps now also in geometry shaders).
A vertex shader is a program that simply takes an input vertex and maps it to its co-ordinate in 2D screenspace. Depending on what effects you might want to apply, there's many different ways you may wish to do that transformation, hence the move from fixed function transforms to vertex shaders. I'm not sure if 3DS has a fixed function transformation pipeline or has programmable vertex shaders (?)