Brushes moving around in hammer?

obodobear

L4: Comfortable Member
Mar 15, 2016
172
32
Ok so this is an issue I've noticed a couple times before but not thought much of it, but recently I have noticed it more. Sometimes when I open up hammer I notice that brushes have moved slightly, usually just by 1-3 hammer units. I've just thought these were mistakes on my part but recently ive seen it moving more like an entire roof off of a building and bad looking overlaps. Does anyone else experience this issue or know why it happens?
 

ibex

aa
Sep 1, 2013
308
528
This happens when you create invalid brushes that have concave geometry. Hammer will attempt to remake the brush as close to possible while creating no concave faces. In the future you can check if you have created any concave brushes by using the problem checker (hotkey: alt+p).

Concave faces will show up as working in hammer after you've created them, but when you save or compile your map they will change.

More info
 

obodobear

L4: Comfortable Member
Mar 15, 2016
172
32
Thanks for the help! I didn't know about that hotkey so i got some other errors fixed too.