Texture resolutions for movie character. How to fit UVs?
polycounter lvl 3
I have a character that i would like to have at 2k resolution for texturing, but I don't know how to fit that in the 0-1 space of a 2048 map. The UV shells are so masive they won't fit even if using UDIMs. i'm new to this, so i may have misunderstood how this all works. Help please. 
Replies
Yes and no. If you go with 4k textures but would need much much more resolution you need to cut your shells in smaller pieces to get the desired resolution on mutiple UDIMs.
Your answer is kind of misleading. It kinda sounds like you need different layout and scales for different resolutions.
I think a bigger problem here is that he is misunderstanding how this whole thing works so it would be better to clear that up first, and then go into some more advanced concepts such as udims.
If you use 0-1 the only option is to use a higher texture resolution.
0-1 space:
You will use one set of textures, uvs are contained within 0-1 space regardless of the texture resolution. There is an exception with tiling textures, where the uvs can go outside of 0-1 space since the texture repeats.
udims:
Different concept, you assign a different set of textures to each space. Still the uvs would fit 0-1 space but they are offset to 1-2,2-3,3-4 and so on.
While udims can increase the effective resolution, you can still increase it further by using larger textures on each udim.
Udims are widely used in movies and cg animation in general, and they are available in games now, however, its not common to use due to the larger memory requirements. If we are talking about non game related stuff, udims is usually the way to go. But its important to mention that material IDs technically provide the same result at the end of the day. But there may be some limitations to this in 3d texturing softwares, while udims are limitless (in a good case).
0 means first pixel and 1 means last pixel. So the resolution is irrelevant here. It would be super painful if you would need to change the uvs if you want to change the texture resolution.
And if you want to use one single texture sheet of 4096px or 8192px, you can create another UV map, copy your first UV coordinates, paste them on the second UV map, and pack all again. That should take a few minutes, and you could see which one offers the best look for you.
Scaling down your UV shells a 50% is not a problem if you use a bigger texture size. For example a 4K texture.
I don't like the way you replied me @Obscura, are you upset, angry or something? what can't you believe?!! did we commit heresy? we disappointed you?
Seriously, Instead of throwing bullshit over us without sense, elaborate things with arguments, and show manners. Later, if someone reply you in a harsh way, don't play the victim role, and much less, reply us like a politic; don't dare to say "the same with different words". If you did wrong, you did wrong, there are no shades of greys here. And for god's sake, don't try to make others to look bad using sly and dirty known methods, distorting what others said on purpose, it's very evident what you are doing. Don't troll us.
Do you want to know what's going on here? We are trying to help while you are confusing people. that's all.
If you want to say someone is wrong, and correct him/her, at least... say the reason/s well argumented and don't raise Cain out of nothing like you did (you won't have more reason), we are not idiots and we are not wrong here, that's for sure. I think you are confusing all the terms and translating your confusion to others. You are the only one misleading here, playing as the smart-arse, and you are complicating things more than needed, when they are so simple. The worse is that you are like "arguing stubbornly just for the sake of having reason". And yes, yes... you are in that "mode". It's pretty evident.
Being honest, I didn't like how you replied to Oglu, very vehemently. All what he said was fine and correct. I thought: "what's the problem with this guy!? the sin of arrogance/pride and the inquisition is here?. In fact, i didn't want to enter in discussion, so i just replyied to the OP. If you don't understood what others said or what i said, it's your problem.
Don't be such a smarty pants. You don't know ALL.
OK, let's enter into your game... The OP said he would like to have 2k maps, so using a few tiles (2 or 3), UDIMs, would be a reasonable option. As another option, he could pack all.. and use just a single texture map. I explained myself very clear, and i'm repeating it again. And I did not stated any necessity, it was just 2 suggestions for his case. Where did you read "necessarily need"? between lines? why did you mix all what i said? you did it on purpose? surely.
If you look better the images posted by the OP (please, take your time), you would notice that all the chunks can be scaled down a little to fit properly in one UV map/space. The 50% was a figurative number dude. And come on, what did you understand to be asking me that? "50% space usage"? huh? why would that be needed for 4k?. You must be the typical guy that doesn't understand the statement of a problem. Again, if you had read what the OP said, you would know that he would like to have 2k maps... but no, it's funniest to argue with people.
If you don't understand it, just do a simple exercise and try it yourself. If he scales down all the UV chunks, he will need a bigger texture size, yes or yes and there's no discussion here. And the reason is simple: we NEED a good texel density, we need enough texture resolution for a good render. It's something logical, so simple that hurts to explain. It's just a matter of texel density and choices, and it seems you don't understand that at all.
This is what happens when you argue a lot, you don't read well, nor understand anything, and you interpret whatever is crossing in your infuriated mind. You end making wrong assumptions.
I readed that reply but i ignored it, but now that i replied you, i'm gonna reply you that aswell. Don't you think you may be wrong? i think so. What you said is truly misleading, confusing, be aware of that.
He doesn't need to change anything in the UV map. What do you understand by "changing the UVs"?. He just needs a simple UV packing as much. The different UV parts/chunks are well mapped, and correctly relaxed, he doesn't need to change how each different part is mapped. And he can do the packing using 1 UV map, or various UV tiles in a matter of seconds or some minutes by hand.
super painful... hah! i smile with that.
To avoid any possible stubborn arguing about texels: https://en.wikipedia.org/wiki/Texel_(graphics) (sorry, i see you coming). More info: our friend Google.
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@macke, you don't need to worry about the UV map size, don't let others to fool/confuse you. An UV map or UV tile will be always a box shaped space, equal to an unit, like in the image above. One thing is the UV map/space and another the texture size/resolution. The bigger the texture size, the higher the texel density.
And like if you wanted to have a rectangular texture (1024x2048px), a 32x32, a 64x64, or a 16k texture. UV map/space is independent of texture size. The image you load will adapt to the UV coordinates, always.
On the other side, Texture resolution is very relevant to texel density. In videogames, It's not the same to have on screen 2k textures than 8k textures. The difference is brutal in a 4k monitor. Furthermore, texel density depends of 2 main things: Texture map size, and UV map optimization (less wasted space = more texels used by polygons). Being said that, a 90%+ of UV map usage is ideal (like PSUs energy efficiency labels). Taking advantage of UV Space is very important, only a few ones here -in this forum- can do proper UV mapping. A model with a really good UV map optimization can use a smaller texture (that was very important years ago), and i don't talk about symmetry use but model topology and seams. (image down)
In your case, you did a good job, and i suppose you can't optimize much more the UV parts.
UDIM is the ideal solution when we need more texture details/resolution in a model, and we don't want to use a single ultra hi-res texture. In film production, in which we need to surpass the limits, the texture resolution needed is usually bigger than the Max Texture Size of the GPU (8k and 16k for newer cards). And the unique solution is to use UDIM, that is simply an automatic UV offset system that assigns an image onto a specific UV tile, which allows you to use multiple lower resolution texture maps for neighboring surfaces, producing a higher resolution result without having to resort to using a single ultra high-resolution image.
If you want to use 2k maps, the UDIM option is a good choice in order preserve details or gain texture resolution, but only if you need 2-3 tiles. Using 4 UV tiles with 2k maps, would be like using a single 4k texture sheet. That's the reason of why we suggested you to use one bigger texture. I would use a few maps of 4k.
In a high dpi render or UHD frame render, all characters will need great texture detail. Close ups are always there, and each model is different. Sometimes we need to have 8 sheets of 8k, and other times much less or more. All depends.
So, if a single texture is not enough and you need to have more details/resolution, use UDIM without fears. But don't forget the max tiles per horizontal row is 10. The use is like shown in the image.
I hope it helps. UDIMs are not a problem with a good GPU/software and mostly all software is compatible with UDIM nowadays.
https://docs.substance3d.com/spdoc/udim-144310352.html
That being said, I may have went a little bit too far.
It's very useful in games, and we usually don't need to change that value doing assets or characters. I usually use 1024.
In modo, that tool allows you to quickly scale the size of UV islands or individual polygons such that they span roughly the same number of texture pixels per meter of real size. You are basically indicating a world space unit, or meter, will have assigned a texture of certain size (1024, 2048, 4096, etc.). If you have 2 meters/units that texture will repeat.
And you know, with models all is a bit different, we only need to have a good uniform level of texture detail. But with level design, this is very important.
Here's an example (the smaller box is a 50% smaller):
As you can see, UV islands are scaled to match texels density. Once we have the texels 1:1, we will need to do a packing for our UV map, and all the chunks will be scaled again, maintaining proportions.
Some packing algorithms use automatic texel uniformity (all is auto-scaled), so we just need to do the unwrap as much.
Here's a nice video about UV mapping and texel density: