improve uv docs

[nickdesaulniers]

currently the docs for atlas.uv() state:

var uvmap = atlas.uv();
/* {
              TOP   RIGHT  BOTTOM  LEFT
  'name':  [ [0,0], [1,0], [1,1], [0,1] ],
} */

When I think of a quad, I think of four pairs of points, so instead of TOP, RIGHT, BOTTOM, and LEFT, I would expect something more like TOP-LEFT, TOP-RIGHT, BOTTOM-LEFT, BOTTOM-RIGHT.

[nickdesaulniers]

The order looks to me like BOTTOM-LEFT, BOTTOM-RIGHT, TOP-RIGHT, TOP-LEFT. I assume you're using uv coordinates where the origin is in the bottom left most corner? Because the existing docs don't suggest that either are correct?

[nickdesaulniers]

Assuming the origin is implied to be in the top left, which I guess makes sense for canvas 2d, then the order is TOP-LEFT, TOP_RIGHT, BOTTOM_RIGHT, BOTTOM_LEFT. That's really going to trip up someone looking for uv coordinates if they're assuming uv coordinate system.

[shama]

This library was originally written for use in voxel-texture. The coordinates are based on what is used in voxel.js and three.js. I'm happy to take a patch for improvements though. Thanks!