UV Smoothing on Subdiv Objects

[azurecgi]

I know this is not exactly a bug, but I feel there should be a workaround, I just can't work it out!

I want to UV texture a repeating thread texture (for bump mapping ultimately) to a subdiv bolt model, but as you can see, when you subdivide the object you get an awful seam thing happen due to the UV Island edges not being smoothed. When I did this in Lightwave, there was a UV smoothing option to only pin the corners and smooth everything else which worked fine for threads!

Does anyone have a good workaround for this that doesn't involve adding loads of extra edges/geometry?

[azurecgi]

bump

[Hirazi Blue]

Does this affect "true" subdivision objects of the "Create > Poly. Mesh > Subdivision" -variety)? Or does it "only" occur when subdividing using the geometry approximation (+/-) method? Or both?

edit: quite a quick bump, btw. ;;)

[azurecgi]

It happens with both, but I am referring to the +/- variety as I want to keep the resolution flexible depending on how far away elements are from the camera, plus some meshes I want to smoothly deform.

I know why this is happening, it's due to SI having a restricted amount of options for subdiv uv smoothing. It's either off (which causes different, but still annoying distortion) or on (which uses the 'only smooth internal polys and leave the edges linear' option). Other software (Lightwave for example) allows you to choose from 4 different options, the 2 you have in Softimage (off and only internal polys smoothed), as well as everything smoothed and, the one that's useful for things like cylindrical mapping, corner pinned smoothing.

Sorry for the impatient bump by the way, it's just this issue is holding up an urgent project, and I really need to decide on how to resolve it by Monday morning

[Jesse]

Theres an option in the UV editor (there may be another way to access this but I'm not sure) File> UV Properties: The option to turn off smoothing is there at the top (Smooth when subdividing), it may not do what you want it to though since it's the same toggle you were talking about.

[azurecgi]

I know of all the available options and how they work.

I suppose what I'm asking for is a decent 'workaround', but also I'm pointing out that I think the range (or lack) of options is pretty poor for what is supposed to be 'high-end' 3D software. I feel that the 'only smooth internal edges/poly' option we have is one of the worst for causing seam distortion!

[Mossman]

I know this is very annoying. In C4D there are also options to fix this problem with one click. As you mentioned the most obvious way, would be to add additional edges close to the seams. Your model isn't very heavy, so that shouldn't be a big problem I guess? I have another workaround which I use when adding additional edges would screw up the smoothness of my mesh. It doesn't work very well always, but in some cases it helps to at least minimize the distortion a little bit: duplicate your geometry, local subdivide to heavy geometry, recreate your UV's and GATOR these new UV's back to your lowres geometry. As you can see in the screenshot it's far from perfect, but depending on your geometry, it can make the trick...

[azurecgi]

It's stuff like this that makes some of us mad when Autodesk lump us with a bloody 'crowd simulation' plugin whilst low level basic productivity tools like UV Smoothing options just get left year after year

[iamVFX]

In C4D there are also options to fix this problem with one click.

And what it's doing during that click?

[just noticed that local subdivision refinement command in keyboard mapping options have no hotkey to choose]

[Mossman]

Good question... I've already intended to do something similar in ICE, but with a quick search I couldn't find any info how UV subdivision is done in C4D. You've got three modes for UV subdivision:
standard - which works like Soft "smooth when subdividing" off
boundary - "smooth when subdividing" on
and EDGE - which usually fixes problems exactly the way you would expect.

[Hirazi Blue]

Although this "technically" isn't a bug, but feels, smells and tastes like a bug nonetheless,
wouldn't it be an idea to post it in the "Autodesk Approved" Bug Thread over at the XSIBase?

[nbreslow]

Hiya,

I have gone through all of this nonsense before and IMHO it is one of the most neglected issues going. I am a Bodypaint user, though I use Mudbox more and more to paint, and wanted to find out some of the same information you are interested in. I posted this over on CG Talk: http://forums.cgsociety.org/showthread. ... &t=1019974. Basically the C4D documentation (for Bodypaint anyways) is wrong, see my post for a breakdown of the options and what they really mean.

I posted all that because I was looking for the Maya/Mental Ray equivalent UV smoothing options so my paint would match up at render without seams. What I found out is that, while you have some options to control UV smoothing when using smooth mesh preview, you have no real way to control UV smoothing when using approximations. The problem extends to Softimage as well, I believe. You are absolutely right about the 'best method', and Mental Ray has the ability to tag corners and do it the way you want. Unfortunately Autodesk has not implemented these features, at least not into the Maya translator - maybe someone can comment on the Softimage side? I have been posting about this on the NVIDIA forum here: http://forum.mentalimages.com/showthrea ... roximation.

Sorry for the Maya heavy post but it has been driving me nuts. If someone can figure this out in SI that would be terrific. Thanks,

-Nick

[Mathaeus]

Hiya,


I posted all that because I was looking for the Maya/Mental Ray equivalent UV smoothing options so my paint would match up at render without seams. What I found out is that, while you have some options to control UV smoothing when using smooth mesh preview, you have no real way to control UV smoothing when using approximations. The problem extends to Softimage as well, I believe. You are absolutely right about the 'best method', and Mental Ray has the ability to tag corners and do it the way you want.

As far as I know (I may be totally wrong, of course) in Softimage, subdivision is performed by Softimage, not MR. MR gets only triangles to render, This is from old times, when MR didn't have (usable) subdivs, so let's say in times of XSI 4 and Maya 5, XSI user was able to put anything to render in MR, without seeing a well known Maya message about non-manifold polygons.
But... once MR got his own subdivs, those were not be compatible with existing implementation in Soft. That's why is not easy to get pTex through MR ccMesh, displacement behaves differently...so on.
Regarding UV smoothing, most likely, what you see in SI view port, that's what you can get.