Hi every one!I have a questtion:how to to make invisible collision boundary for my level ? so that player can't falling out the scene accidently.coordinate limit would work but I think it's too simple,because I want invisible obstacle in my level(we can't just use model every time,right?).

Manual offers two method:
1.'invisible' flag for entity and block,but they don't have collision.
2.block with 'none' flag.they have collison,alomost there.But,they will also "block" the light and cast shadow,clip other block and entity,and if it's in front of the camera it will clip the level.(see the picture below)



I know you have met the same situation,so can you tell me how you do it?

Set thier polygon flags on or give them a high push value (set invisible)

Thank you,Nems!
It works.The point is using model instead of block,and set invisible,use bbox or polygon.
I draw invisble wall using blocks in WED and then export to mdl and import back in(maybe center the pivot in MED).