I've playing a bit with the amazing glgraphics lib, trying to learn how to handle models, lights and stuff.

This may sound noob/silly, but, when vertices are stored in its floatBuffer (model.vertices), it stores x,y,z and a 4th value. Whats this 4th value and what does it stands for? (it's set 1.0 by default)

I'm playing with a sphere model (in fact, it's an icosahedron i subdivide to make it look like a sphere). After it is calculated, I want to "distort" some of its vertices to get some "peaks". I've been trying this by modifying a certain model's vert, but i'm not sure which value should be modified to achieve this.

This is a basic sketch of what i'd like to achieve. Any tips? Thanks in advance!