Creating new stages?

[JackThorn]

I've seen, in some project threads that people have managed to completely edit some stages.
Now, I already know about model swapping, but what about collisions for the stage?
Does it have to be hexed? Is it automatically generated based on stage geometry, or do I need some other program.

I tried looking around this help/tutorial section and didn't find anything regarding stage editing.

 

[Mr.Chuy]

collision editor in brawlbox fix a miscdata that's blue and hit ctrl+p

 

[KyuubiDemon1]

what does ctrl+p