How to get correct texel density unwrapping LARGE object with multiple pieces for substance painter

99isthebest

I have a large object (a vehicle) it has multiple objects I've modeled it in 3ds max.

I'm having issues figuring out how to get the correct texel density across all the objects so that when i bring the model into substance painter I can have decent looking non distorted maps. I've found tools that help you set the density etc. The problem I have is the biggest object (the hull of the vehicle) obviously takes a huge amount of UV space. If I then apply the same amount of density to a smaller object it has such a small area of UV space that its pixilated and useless.

just this object alone takes one 4096 map forget the other 100+ objects in the scene

when applying the same density to a small cylindrical object the density is too small to even see.

I get that its acting as if these two objects were on the same 4096 map. But how to i give this smaller object more density when i can't increase the large object without going up in map size? if that makes sense.

To be honest I think I'm going about this all wrong. I've heard of Udims, but i figured since this is purely for a rendered image if i had say 4-6 4K separate maps it may work. If anyone has any tutorials or suggestions about how i can unwrap this object I would greatly appreciate it. 

HAWK12HT

Texel Density is a guide not a 100% must, been through this learned the hard way. 
https://80.lv/articles/textel-density-tutorial/

*for items smaller than main bigger shape you practically eyeball and scale those UV islands up a bit till they get decent enough detail and dont get pixelated. 
*3-4 4k maps for current gen hero assets is a norm.
*you gotta balance TD and wasted black pixel space on texture, that usually comes from tech dept in a studio. Like if you end up having an island on its own with plenty of space around so to have it as a separate texture or merge it with existing island on previous texture. 

Hope this helps

99isthebest

Hey thanks for the advice, That article looks really helpful. I guess as you say it’s not 100% essential to have the texel density entirely the same.

gnoop

Texel density is a weird dogma surfaced suddenly at some point during past decade.   Before nobody cared.  It had always been UV efficiency first .   In many cased varying texel density could be a tool  actually .  A way to prioritize or hide to certain extent too low res nature of unique unwrap.    When an object doesn't fit well into a single texture and not worth another draw call etc.    Just do not do it more than x2 scale difference.   

It became a mind imprinted  dogma finally  due to soft such of  Substance Painter   that does  its  procedurals in UV space.  Before we did same things  baking procedural 3d shaders using object or world space  and the texel density wasn't a problem at all. 

  Still you could use triplanar projection in SP to workaround density inconsistency. 

Mark Dygert

(Puts on grumpy old man pants...)
The whole, we don't bother to learn why the rules exist but we sure do enforce them have spread that garbage pretty far. This isn't aimed at anyone particular in this thread but it's how this stuff spreads around so easily.

"Tris are the devil! ALwAyS uSe QuaDs!"

Bullshit.

"Texel density is SUPPER IMPORTANT!!!1" 

 Only if it becomes an issues, either visually or technically.

Sometimes I wish there wasn't a way to compute it and have some kind of measurable stat, those seem to trip people up and cause more busy work than there really needs to be.

"BUT some player might use a model ripping tool. Then run it through some DCC app, combined with a custom script that they downloaded to compute texel density and then POST IT online for EVERYONE TO LAUGH AT!"

They'll laugh alright. At how many hoops that guy jumped through to be nit-picky about something no one cares about. Seriously, burn your Texel Density Tool script. You'll probably save yourself some time and reduce your stress, lol.
(That was aimed at the OP, you're being a bit ridiculous but better here than on the job somewhere, lol)

OK, back to being helpful...
With big objects like this it can totally become an issue and there are a few ways to solve it depending on your situation.

A ) Does it really need 100% unique pixels everywhere? Can you use some tiling textures to get the densities closer?

B ) Can you use multiple textures for different areas? Sometimes there is a good material break and separating the areas makes sense, like cloth interiors and hard metal plates. They both might benefit from a texture split. Maybe it makes sense to split the shader too so you can do a particular trick like sub-surface scattering on the cloth that you don't want to do to the metal and masking it would just mean more textures and a more complex shader.

C ) Is there a way to imply a higher density while using less? Are some areas relatively large areas devoid of detail but certain parts of it need higher detail? Can you cut the mesh so you can upres that one part without having to scale the whole thing? 

D ) Can you use decals and hovering planes to pack in details? Lets say you wanted to put the name of the ship on the bow. Rather than baking that into a giant UV section of the bow, put the name on a small hovering plane or depending on the engine use a projected decal.