The Minecraft entity collision code, as I just learned, is sadly lacking. The entity code is configured, by default, to allow a square prism. What if you want a bounding box with custom dimensions? Override setPosition. Easy enough, until you start trying to work with rotation. For example, I'm trying to make a tractor, which is obviously longer than it is wide. I want to allow it to turn. Easy? No, because the bounding box is axis-aligned.

 

I'd like to request, perhaps as a long-term goal, that a non-axisaligned bounding box system be implemented. This would allow for better entity collisions universally.

As all bounding boxes are axis-aligned, the intersection detection (for collision etc) is very easy. if you take a non-axis-aligned bounding box, the complexity of the collision checks increases drastically. So this would be a bad idea as it would harm performance.