[more or less solved] monsters unable to walk over stairs

[Cacowad]

i first encountered this problem here(shameless plug warning): http://www.doomworld.com/vb/wads-mods/69433-heretic-domus-revisited/

every monster there can walk over a couple of steps, but after then they seems unable to proceed further, and i have absolutely no clue why;
this behaviour is aspecially clear in the cave part, where there are a lot of steps.

(btw,the incriminated steps are 16px tall).

any help would be greatly appreciated.

[joe-ilya]

Because there's a 'block monster' line on one of them?

[Cacowad]

i don't use that flag. also no, this isn't the case.

[Vermil]

The stairs need to be big enough for the monster.

Where as the player can move over ledges of any height, a monster's can only move over ledges up to 24 unit's high.

Naturally, bigger monsters require bigger steps than smaller ones.

[mouldy]

I think as a general rule, if any part of the ground under a monster has a height difference of more than 24 units (from lowest to highest point) its going to have problems. Eg, if your steps are 16 units high, the monster isn't going to be able to cover more than 2 steps at the same time

[Xaser]

A related thread (with an exceptionally on-topic title) on the topic can be found here: http://www.doomworld.com/vb/doom-editing/55704-demons-are-scary/

Haven't seen the wad linked in the OP yet, but it's likely related to step "depth" (as described in my post in the linked thread). I think that's what Vermil n' mouldy are getting at.

[Cacowad]

Xaser, the post you linked is what i needed.... in fact 16 units tall steps can be too big for monsters to navigate (thank you doom AI), but only if placed too close to each other.

well, seems like i learned something new today, thank you all for the assistance.