[3ds Max] How to apply different UV-maps to different parts of the same model?

Dubious_Fellow

Hello good people of Polycount, I have a large model I want to break down into separate uv-maps so I can apply separate (2k) textures. How do I do this?

-I stumbled across the multiple UV-tiling method called "U-dimension" (or "UDIM") and it looks perfect for what I'm trying to achieve. But the old tutorial I found requires the use of Composite maps and my model is set up with a Multi Sub/object ready for export to Substance Painter (the Mat Ids and Multi-Sub/Object are already applied, I'm at the stage of unwrapping it).

Is multiple UV-tiling the way to go, or is there an easier way?

Here's the UDIM tut:

http://www.neilblevins.com/cg_education/multiple_uv_tiles/multiple_uvs_tiles.htm

EDIT: Could I literally cut my model up into 3 parts, unwrap, export and texture in SP individually -before reattaching in max after? Would the reattached model still have its 3 separate UV-maps?

danr

You don't need UDIMs. If you already have a multi-sub object material and IDs set up on your model, you've already done what you need to do, each ID will have its own UVs.

so just edit UVs for each ID like so ...

... and you're ready to go.

(edit - i just read the tutorial you linked to. It is bad information).

Dubious_Fellow

danr said:

... and you're ready to go.

Thanks Dan, as you can probably tell, I'm pretty green when it comes to texturing/mapping. I should probably elaborate;

I'm trying to unwrap and texture this beast:

The pro who's been helping me has recommended that I use three or more 2k maps, and that I divide the ship up like this (with a 4th texture for the deck structures):

At the moment all of the objects that make up the ship are still separate. My plan was to unwrap each piece individually and then put them on the 4 texture sheets.

-Should I attach everything together before unwrapping? (am I right in thinking that you can't attach objects together after you've unwrapped them? -that involves going down into the Editable Poly Modifier and breaking the Unwrap?).

-Also, am I correct in thinking that you create new textures using Map Channels?:

 

After reading your answer I duplicated the existing Mat IDs twice, renamed them either "_Mid" or "_Aft" and divided the largest piece up into 3 separate groups by applying the new Mat Ids to the respective sections:

I apply an unwrap mod and move one part of the forward section to a new map channel (channel 2 while the rest stays on channel 1):

When I try going back to Map Channel 1 to get the rest of the forward section I get this warning text:

...so after a week of annoying people and banging my head against the desk, this is where I'm at. If you (or anybody else) could enlighten me further it would be very much appreciated!

danr

nooo, don't touch the Map Channel dialog. That's for far more complex operations than you're doing here. As i say, you've already done everything you need to do.

don't think of UVs as some delicate flower which will fail if you breathe on them from the wrong direction. When you edit UVs, all you're doing is changing the UV coordinate of each vertex which is stored in the vertex itself, and will then export/import as such. Its impossible to make them "dissapear" short of stripping them out of the exported model. You can mess them up, sure, but in Max, they can take some real punishment. Most of the simple operations you'll do as a modeller will leave them untouched, especially in the 'my model is more or less finished' phase ie the unwrapping.

the other thing which i *think is confusing you, is that you seem to be working under the assumption that every vertex on a model needs its own unique space? It doesn't. Vertices across a model can share UV co-ordinates. Say you split your ship into 3 objects, unwrapped them, and attached them back together. When you view the UV Edit window from the default view ("All IDs" at the bottom) it looks like an absolute mess, right? Well thats fine, as long as each section has its own ID. The dialog i pointed out in my first image is the filter, which allows you to view and work on the UVs for each ID separately. And thats how Substance Painter and your game engine will see it - each texture set/material essentially acts as a filter

btw - as suggested above, you could indeed split your model up for UV mapping before attaching it back together. I do this myself frequently (also prevents you working on the wrong ID in the edit window, which is easily done). The reason i didn't suggest it, is that i don't know your model - breaking it apart and reattaching then welding verts would break smoothing groups and custom vertex normals. But if thats not an issue for you, its a perfectly valid method (its preferable to make sure you have a manually created multi-sub applied to all your objects first though. The other way of letting max sort a multi-sub itself can really confuse beginners)

(ps ... if you're taking this into substance painter, i would suggest breaking the model up into sections that will share the same type of texture, rather than doing it front/middle/back. So think about splitting off the hull metals, the deck, other parts of the superstructure. If you do it front/middle/back, you'll need to rely on Instancing in Painter to get all your texturing consistent, and thats still a bit flakey and restrictive, eg you can't instance paint strokes)

danr

hey

i've just realised something which may be sending you off on the wrong tangent, but its unclear from your images above (i'm not sure what steps you've already taken).

when you apply your multi-sub, your boat doesn't want to look like this :

it wants to look like this :

that is to say, if you've already used materials to help describe your boat, get rid of them before starting this process. 1 material ID for everything that you want on one texture. 

(well don't get rid of them entirely. Keep a copy of your original model/materials and use them to bake an ID map in Painter, which will be invaluable)

EDIT - after reading your reply again, i'm pretty sure this is where you're going wrong. I didn't read "I duplicated the existing Mat IDs twice, renamed them either "_Mid" or "_Aft" and divided the largest piece up into 3 separate groups" closely enough sorry.

You don't want groups of anything. And certainly don't try and nest multi-subs inside others, yuck yuck, totally unworkable.

This and this alone is what you should apply to your model :

note that the name of the Multi sub is irrelevant, thats just for max. The important name is what you call each Sub-Material, this is what Painter will name its Texture Sets by default, and also what an engine such as Unity will import materials as. Note, the "Name" slot does nothing in terms of Painter etc

Hopefully this clears everything up

Dubious_Fellow

danr said:

Hopefully this clears everything up

Oh man, thank you so much. Everything makes sense now!!

-I watched an SP video on YouTube where the guy makes and exports a dedicated Mat ID version of his model (using a whole bunch of ID's). I did wonder why he didn't just put them on the original ...this is why! (I did ask, but they didn't reply.)

-The only small thing that is still confusing me is the role of smoothing groups in texturing. SP recommends exporting your Low with just one SG (presumably because all that geo info is stored in the high poly normal map?) So why would breaking the smoothing groups on the Low be an issue? (-when breaking it into 3 parts and then reattaching).

Eitherway, really can't thank you enough, this all looks soo much simpler then the cluster f*** I've created!

danr

The science of baking is far too detailed to go into here, there’s lots of info on the wiki and all around. Suffice to say, the vertex normals (smoothing groups, hard/soft edges etc) of the low do have an effect on what the model looks like in the end, and how the baking is achieved to get it there. “Give everything 1 smoothing group” is a huge oversimplification 

Even if youre not baking from a high poly, you’ll also find that smoothing groups greatly affect your mesh maps in Painter, particularly your curvature map, and therefore how generators and so on will work

tbh, if you’re  unsure or confused, you just need to get in there and try it out. A lot if these answers should be self evident with a bit of experimentation