Piston is a mess, documentation wise. It's got like 50 different things called `Texture` and they're spread across 20 modules and every function you'll want to call is hidden under 5 layers of trait indirection.
I'm exaggerating, of course, but my experience trying to use Piston was absolutely miserable. Next to zero documentation, with endless layers of confusing abstraction. It's designed to have swappable back-ends, and that's a big hassle when you don't care about that.
[1] http://www.piston.rs/
[2] https://github.com/PistonDevelopers/piston