Is the collision model included in pathfinding?

[Destined]

Hi guys,

 

I have wondered, how the AAS decides, if paths are available for AI. Does it take the collision model into account or does it just calculate the width and height of passages and depending on that decides if the average AI should fit / not fit through that passage? Or to put it differently: does the collision model of an AI influence the path finding algorithm, i.e. will the AAS notice that a bigger non standard collision model is too broad for a regular passage or the other way around, that a smaller collision model would enable the AI to walk thrugh a smaller gap?

[Bikerdude]

I beleive the engine treats collision brushes the same as monsterclip/clip.

[grayman]

Simply put, each AI has an AAS size that's used to construct a world for him to walk around in. In the case of the human AIs, that size is 32x32.

 

Dmap constructs a map of AAS areas whose edges allow the AI to walk to w/in 16 units of walls (world/monsterclip/etc. brushes).

 

Non-symmetrical AI (i.e. the horse) still have a square AAS size. So if a horse walks close to a wall, then does a 180 degree turn, his head or butt will swing into the wall.

 

The collision model (or bounding box) of the AI really only comes into play when the AI encounters func_statics or moveables or projectiles or other AI or the player.

[grayman]

Addressing the 'height' part of your question ...

 

Dmap won't create AAS areas for an AI in passages that aren't high enough for him to fit through.

 

Humans are taller than rats, and each has a different AAS size.

 

If you want your rats to be able to run beneath tables, but you don't want your humans to bump into them, you can surround the table with monsterclip, then lift the bottom of the brush off the floor so there's room for rats to run underneath.

 

I also recommend that when you create a monsterclip brush around a func_static that you normally wouldn't want an AI to climb up on (like a table), that you lift the top of that brush up to the ceiling. Otherwise, dmap creates AAS areas on top of the brush and pathfinding's job at runtime takes that much longer when it has to deal with more AAS areas than you need.

[Destined]

Ok, I see. Thanks! Then another question: would it be possible to change the AAS size of an AI (or where can I see, where it is defined)? My plan would be to give the AI a smaller AAS size, so the AAS thinks, that the AI would fit into a small passage. This I could then use to let my ghosts walk through walls, by creating a small gap on the bottom of a wall (that I could seal with nonsolid brushes to hide the fact, that there is a gap). If this works, only the ghosts could walk through the gap, but the player and other AI could not. It's not the most elegant solution to the problem, but it would work...

[grayman]

On your ghosts, set these spawnargs:

 

"size" "10 10 6"

"use_aas" "aas_rat"

For the passages the ghost will use between walls, make the openings 16 wide by 10 high. Put visportals across both ends.

See what happens.

[Destined]

Thanks a lot! The aas_rat worked. I used a gap at the bottom of a wall, that I filled with a nonsolid wall, so the player can't see it. That way it looks as if the AI walks through the wall while other AI can't. Of course, in this setup rats would also be able to walk through the fake wall, so I might just use a custom "use_aas" for the ghost. I wanted to make it as small as possible, so the player does not "feel" any resistence while walking through them. But now I can finally make only the ghosts walk through

Edited November 18, 2015 by Destined