Question about UDIMS

stephanieroach

Hi all, I wanted to get some advice here because I feel I may be missing some fundamental knowledge of UDIMS, hah.

So I have a creature modeled in Zbrush that will be used for a film. I mapped it with 10 UDIMS in maya before starting my texture work in Zbrush. As a test, I duplicated the model and made a single UV tile version of it, just to compare between them. But after applying the original 10-UDIM textures to the single tile version and doing an Arnold render of both of them together, I saw no difference in the fidelity of the detail. I’m confused by this, since shouldn’t the 10-tile version look much better than the 1-tile version? What am I missing?

iam717

Yeah, Since we are on the topic, 

I've recently seen a video breaking down for this process about cloth&udims, however isn't per-tile just an equivalent of 1 4k map per uv tile?  (which is cheating when "game" engines are restricted aren't they? "less is more")

i immediately thought this and if it is not, how then do these per-tiles per-uv's conglomerate into 1 4kmap and retail all that quality? (you can see i clearly haven't played with udims yet)

This is a perfect double question.

 (This popped into my noggin just yesterday and what do you know someone brought up the issue)

poopipe

important point A:
UDIM is nothing more than a naming convention, the mechanics of how the result is handled are entirely down to the renderer/engine/whatever. 

to the original question... 
images would really help diagnose the problem. 

if you use a single 4k map and you lose no detail compared to your sculpt then using 10 4k maps isn't going to make it look any better. 

if your single map does not capture all the detail and the UDIM looks the same there might be some sort of problem

stephanieroach

poopipe said:

important point A:
UDIM is nothing more than a naming convention, the mechanics of how the result is handled are entirely down to the renderer/engine/whatever. 

to the original question... 
images would really help diagnose the problem. 

if you use a single 4k map and you lose no detail compared to your sculpt then using 10 4k maps isn't going to make it look any better. 

if your single map does not capture all the detail and the UDIM looks the same there might be some sort of problem

Here you go, I've attached some files of the WIP sculpts in Arnold. The top model is the one with only 1 UV tile, the bottom has 10. I also shared the 1 UV tile layout vs the first tile layout of the 10-UDIM version. Essentially his head covering a whole tile vs just a small portion of it.

I'm not disappointed with the result I'm getting, just surprised that they look the same. Shouldn't 1 8K texture for the head look better than 1 8K texture for the entire body?

poopipe

with that much detail in the sculpt , I'd expect there to be quite a difference so there's got to be something else going on. 

might be worth uploading some pictures of the bakes  / renders 

stephanieroach

Here are the displacement bakes out of ZBrush (just the head again for the UDIM one.) Original files were 32-bit exr format and red color, I've desaturated them to be easier on the eyes.

Something else strange - on my duplicate model with only 1 tile, it showed like 90% of the displacement without any subdivisions turned on yet. All that was missing was the displaced details from the edges of the model.

pxgeek

It could be that the combined 8k texture is sufficient enough to capture all the information in your sculpt?

Pixelpeeping the renders, it does look like there is more crisp definition in the higher frequency details (crackly bits in the scales around it's lips)

At 8k for a udim of just the head, you're most likely needing ultra high frequency details like micro pores. So if you had that information in your sculpt (and turn up your subdivisions on render) then maybe there would be a larger discrepancy between the two.

stephanieroach

I did ultimately end up going with just one UV tile, since I was getting pretty much the same result either way. So maybe yeah, one 8k was fine for this? Still kinda surprised!