As I mentioned in the last post, the space environment I'm creating is done with Maya Paint Effects. I will now talk a little but more about this intriguing technology.
Paint Effects is basically a way of painting with 3D. Although I am not familiar enough with its inner workings to describe 'exactly' what it is, I can tell you from its results pretty much how it works and what its advantages / limitations are.
First off, Paint Effects is, at its core, a 2D effect. This brings with it several bits of information worth knowing before using them. Its main advantages: it renders blazing fast, it is easy to tweak, it looks pretty. Its main disadvantages: due to its nature, most times you get no alpha channel (as when you use 'strokes'), making them a pain to work with in comp and to layer over each other.
On a more technical side, Paint Effects is a Post Process, which means it doesn't get calculated at render time together with all the other geometry in your scene, but rather after everything else is done, Maya goes in, looks at what paint effects are in the scene, and in effect paints them onto your render as if a blotch of paint suddenly fell on your beautiful painting, and it is equally irremovable. That is also why only Maya software render can render paint effects (other 3rd party renderers like mental ray or RenderMan wont do it).
So basically if you want to have Paint Effects in your 3D scene, you better render them all at once and you better get the exact look you want right off the bat, because there is very little you will be able to do with them after they have been rendered. (if anyone knows otherwise, please show me the error of my ways).
Now I will show you a paint effects image
and its alpha channel, which is apretty much unusable (only fully white areas are fully opaque).
So that if I would like to put something BEHIND the paint effects layer, it would loose all the detail and pretty much look like this: