Hey Guys! I need some help! lol. I would like to make one of my objects so that sims can walk through it, instead of sims just stopping when they reach the object. I couldn't really find a tutorial or something that would explain how to fix this sort of problem. I cant really tell or show the object, cause it's part of a secret project Anyways, any help or words are greatly appreciated! Thanks so much! :D

You can change Init BHAV - add 'allow object intersection' flag to tiles that have to be passable:
[prim 0x0002] Expression (My 0x0008 (flags) Set Flag flag# Literal 0x0005 (allow person intersection))

Or you can edit 'footprint' block in CRES - put 00's where object should be passable; this way would be better if you have complex footprint shape.
Looks like Atavera had deleted his post explaining how to edit this block
I hope noone would be offended if I copy here the content of that post which I had saved a while ago :o

I have a small question - which way is the green arrow of the tile assumed to be pointing in relation to the tile's footprint pattern. Ie in stage 1, would the arrow be pointing towards the rounded corner, or some other direction? I hope this makes sense lol!

Eww... If I remember correctly :-<
Green arrow points to the same direction as Y axis. Tile numbers are (X, -Y) - I mean, first number grows in the same direction as X axis, second number grows in opposite direction as Y axis. Something like this:
^^^^^^^
(0,0) (1,0)
(0,1) (1,1)

However, since the game has this weird axis system - tiles are arranged a bit differently when you write footprint. Imagine that you are looking at the object from bottom view. The tiles will go like
(1,0) (0,0)
(1,1) (0,1)
At least this variant worked properly for me when I was doing the round cabinet from the Round Clothed Curvy set

What I really meant was that when you are drawing your bitmap grid for one tile, is it the top line of 1s and 0s that the arrow is pointing to?

No, that entire block of 1s and 0s correspond to single tile, so for multi-tile you'll have multiple blocks.

Still didn't explain myself properly Supposing it's only a one-tile object - which means just the one green arrow on the ground - which row or column of the 1s and 0s block for that tile corresponds to the tip of the green arrow?

No, it's me who understands wrong
The bottom line corresponds to the tip.

Thanks Sometimes written words are just not enough - do you think that's why people have developed the technique of waving their arms when they talk in person?

Just reporting back that the "update footprint" turned out to be the solution, so thank you for that, my towels are working now

The only slight, but more or less insignificant, thing is that the sim who is actually on the towel doesn't seem to work out she can walk over it to get off until she has had time to consider what her next autonomous action will be - when the sunbathe icon leaves her queue. So if you have something else for her to do she will throw a tantrum about not being able to get off the towel. I hate sims sometimes.

Maybe you could try to add 'Allow intersection?' bhav? It's referenced in OBJf. Something like - if sim's interaction object is me, then return true, else return false'. I don't know much about this function, though so if you'll play with it and it'll work, please share the details

I know - I have used allow intersection in the past but it just doesn't seem to be working any more. That's what I happily but fruitlessly coded it to do first before coming to this thread. The sims seem to be completely ignoring it now. It may be one of those things which has changed in later EPs. There appears to be a new setting "Allow walkover" but I had similar (non)results using that too.

Just dropping in to add something for future users of this thread - I'm about 99% sure that, since all this stuff is little endian, you have to reverse the hex digits between steps 3 and 4. That is, you go from this:
00 00
FF F0
FF FC
FF FE
FF FE
...

to this:
00 00
F0 FF
FC FF
FE FF
FE FF
...
and then to this:
00 00 F0 FF FC FF FE FF FE FF

Otherwise it comes out all strange when you try to draw out the maxis footprints.