I've noticed an orange(?) rectangle in the middle of the art pieces. (I'll send a screenshot if needed)

I think I've found and fixed the material issue, will update the addon shortly. Just briefly tested the new materials in SFM but I think it should just carry over into GMod and work fine. Let me know if the problem persists after the update.

I've noticed that for the fish tanks, the creatures inside clip through the bottom of their containers and are rotated the wrong way (like, bigger fish will completely clip through the front sides of their tanks).

Just had a look at the bug tanks, and they have the same problem.

(Also, I don't know if this is just a problem on my end or something, but some reason, the texture for the Coelcanth model stand isn't showing up. All I see is the purple and black checker pattern, below the fish. None of the other models appear to have this issue, though. )

'use ragdoll mover to pull them to the ground where the physmodel would normally cause issues'
...you compiled these models with just a $collisionmodel command and nothing else didn't ya?

yea... is that part of the reason this weird rotation issue is occurring? it seems to be on and off and i don't see any patterns to what's causing it. after looking up some stuff i realize there are options for the $collisionmodel command that I haven't used but i don't see any that would fix or cause the collision model rotation issue

also gonna point out the fish being at the bottom of the tank was just how they were stored ingame, likely because they're animated a bit. you should be able to move them around with the advanced bone tool, though the rotated physmodels again is not right idk what is causing that

first of all my game is slow as hell so i won't be able to test for a few minutes but here's the gist from my end

There's a number of things simply not good with just using 'collisionmodel' in this case, I realise it was to speed things up so such a large number of models could be compiled with ease but it results in many an issue especially with convexwrapping, which if you put nothing else is what it'll do, use the model to wrap it in a convex shape (what I refer to as making it a boulder because that's typically the kind of shape the collision all ends up as)

If you exported them from blender and didn't apply transformations, the collisions end up in all the wrong spots. Of course since this is just $collisionmodel it does seem a little strange but applied transformations are really important. Been testing maps in the back lately, namely a model with very finicky collision. All the times said collision wasn't applied caused it to be offset from its position, causing issues with the model in the map. Now this was custom made collision, which makes it strange if it's flipping it based on those.

collisionmodel does have options. I use two of those very typically because only for some things can simply just putting a collisionmodel command and nothing else can really help. And in those cases, it requires work.

Not sure what those cases are, so I'll be back in a bit

a friend of mine pointed this out too when we saw the villager addon: why are models with extremely similar proportions split when they could be skins? Okay, if this was done by a script to get each individual model sure, but some models are split when they shouldn't need to be. Like KK's song photos, or the new years hats. No polygonal difference, only split by type because in-game they're split by type. It would cut down on an immense amount of space if you made those splits

do you mean the bugcages why they're rotating?

their collision model has an extra notch on the bottom causing them to bend one way since it's not flat

if you want to see the compiled convexwrapping, vcollide_wireframe 1

I think at this point I should probably redo the phys models, I've made custom ones and haven't had it do convex wrapping I believe (been using $collisionmodel "physmodel.smd" without options). I probably got too impatient and cut too many corners but I don't believe I've applied any transformations since I only transform the verts in edit mode and don't move models in object mode.

Also, yea the different types of naming causing the duplicate KK songs and new years hats is a bit annoying since I use scripts and make some assumptions but it's a low priority to fix for me rn since so many phys models are broken and need to be fixed. Technically they work anyway but idk.

the translucency on the cages/models is a bit much. I know some might have been aware i sort of fogged up the glass in maps that contain it, yeah, this was the reason why. Put it to full translucency and you won't even be able to tell there's supposed to be glass there.
Even the models you can't even tell they're supposed to be attached to the stands unless you hover over them in the context menu or pick them up with the physgun. Be nice as a skin but uh translucency oughta be altered maybe

I don't know how you import the models but I presumed you were saying the models have their collision rotate upon compile which if you have custom collision means their transforms need to be applied in object mode so then they aren't offset weirdly (as i've discovered with my own maps in the back).
Also if there aren't any loose vertices, they just clog the vert count for no good reason

Yeah, I've only pulled out a few models and some would definitely benefit from custom physmodels. Disable collisions can only get you so far in some cases (and if it helps, some like the balls won't need that many edits)

I can't really go through my entire screenshots with all the models, but this is sort of the best example i can provide of convexwrapping

https://steamcommunity.com/sharedfiles/filedetails/?id=2465340602

also did the cake use to have a candle?

Yea I already knew what convex hulls were but thanks for clarifying that, if I was speaking weird I meant I didn't have the studiomdl compiler make them for me and I just used Blender to make the convex hulls out of the base models then decimate them to get a lower poly count, and it seems after this convo and my own research Blender is likely the cause of this whole physmodel mess even if I can't pin down an exact cause. As for the cake I'll have to look into that after I fix these stupid physmodels. Shouldn't of rushed the gmod version lol.

well i'm sort of half joking with the tone of it. I intend to really clarify on it at a late date, i'd prefer that knowledge to be public as well rather than be locked behind a bunch of discussions n such.

It's not just the cake it's a couple of them that have weird collision issues like the cages as well. Convexwrapping is everywhere, like the mushrooms, chairs, beds, really any of the models that have weird oddities. The floor seat is just the best example I can really provide of it since it's the most obvious offender of such.

edit: in terms of the studiomdl vs blender bit, functionally there doesn't seem to be much of a difference in the way blender perceives a convex hull vs how studiomdl does it. That's actually sort of part of it, the specifics are a little more complicated than that