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View Full Version : Some UV questions


illusory
10-26-2007, 01:33 AM
Hello everyone,

It seems XSI is geared toward wanting to make a single UV map for an object, which is great for games, but i'm trying to do a high-res character at the moment, and i need to have a few UV maps on my character. How does one go about this?

When i try to make a uv map for a cluster, it includes all the polys in the whole object -- i only want the polys on the cluster to be on the UV map.

So i tried extracting polygons from a cluster, applying a UV map to it, and then copying that UV map back to the original cluster. Well, at first XSI crashed every time i tried this. Later, i tried it experimentally with a sphere, and it copied ok, but the UVs were screwed up when i went to apply a texture to the cluster -- i suspect a point order change during the extraction? I vaguely remember someone saying how to stop XSI from doing this...does anyone know? Picture below shows problem.

I'm sure there are plenty folks who need to make several UV maps for a character at times (like, head/shoulders, torso, legs, arms), and certainly at least sometimes you want your character to be all one object, yes? Will you please share your method for doing this? So far I can only manage it when importing a Lightwave object, where this was done in LW -- when PO works....

In my current case, I have textures already made for these differentareas of the character. They aren't very good, and i don't mind making new ones, but I would like to use a different image for these different areas for several reasons. One is to not make any one texture too large, but still get good resolution. Another is to be able to use them (separately) in Zbrush, and get high enough resolution, working on one part at a time. Another reason is that Bodypaint can use these different textures nicely and make the seams seamless.

I'd sure love to hear that this way of UVing is possible in XSI...if you have a way, please describe.

thanks for any assistance,
NJ

Image shows the proper Uvs on hemisphere on right, which was extracted from the sphere. Sphere on left shows transferred UVs from extraction, not mapping properly, and below shows the texture editor view of the faulty UVs.

Brainsells
10-26-2007, 02:18 AM
You can make more than 1 uv coordinates for an object. Just apply another UV property and collapse the points you don't need; ie the head of a character. Or you can stack your UV's on top of eachother and save out stamps for each part.

illusory
10-26-2007, 06:35 AM
"You can make more than 1 uv coordinates for an object. Just apply another UV property and collapse the points you don't need; ie the head of a character."

If that's the only way, guess I'll have to.

I've been working the "Branch Tutorial" at:
http://www.edharriss.com/tutorials/Branch_Tutorial_files/branch_tutorial.htm
which explains the process you mention, of collapsing unused points in the UV.

Seems like that would increase processing time, all those extra points to read in each UV map, for the render, which are not contributing anything.

But the main problem is, that method makes UVs that won't work in ZBrush (it doesn't tolerate overlapping UVs). Which is a significant issue. If only XSI would allow you to clear UV points off a map. It's maddening that there's no way to do this. In Lightwave you just select the points and 'clear from map'. That was helpful. Guess you can't have everything...(My #1 XSI feature request!)...unless it's in there somewhere and i just haven't found it yet.

" Or you can stack your UV's on top of eachother and save out stamps for each part."
Not sure what you mean here, you mean taking up the same UV space, and using the one UV with different textures on differerent clusters? That's kind of interesting. But still wouldn't work with Zbrush, unfortunately.

thanks,
NJ

Sarford
10-26-2007, 12:04 PM
You can always cut-up your object into seperate objects. It gives a little bit more work at weighting but other than that it works very good. That way you can create very high-res textures for every single object, and your UV's work in z-brush aswell.

This method works only if you have a clothed character though, for an animal this propably wouldn't work.

Sil3
10-26-2007, 02:48 PM
But the main problem is, that method makes UVs that won't work in ZBrush (it doesn't tolerate overlapping UVs). Which is a significant issue. If only XSI would allow you to clear UV points off a map. It's maddening that there's no way to do this. In Lightwave you just select the points and 'clear from map'. That was helpful. Guess you can't have everything...(My #1 XSI feature request!)...unless it's in there somewhere and i just haven't found it yet.
NJ

This was one of my stresses when I switched from LW to XSi as well, in LW we select what we want, make a projection and ONLY the selected polys will be on that projection, no need to collapse, make smaller the extra ones like in XSi... but its the only way that i know to deal with it.

About ZB workflow, yeah... but remember that you can replace Objects in ZB with proper UVs, so by instance you could make your sculpt and bake the Displace/Normal Maps on diferent Objs with the various UVs (one for each .obj), as long and instead of Collapsing the extra Points you make them smaller so they wont occupy too much space.

PITA I know, but this way you have several versions of your UVs for the more detailed parts that you need, then in XSi use those baked texture Maps (with Alphas) to blend them all together on an .obj that has all the UV Maps

illusory
10-27-2007, 12:57 AM
Thanks for clearing some things up, Sil3 and others -- I have a better idea now how to proceed.

BUT, i gotta say i've been steeped in UV nightmares here...like...even Roadkill has turned on me now -- look at these pics!

Very nice unwrap to start with in Roadkill -- but look what happened when i quit, and the UVs were sent back into XSI! This has never happened before. Same thing happened whether i invoked the Roadkill interface or not. Even with a restart..

Any clues???
thanks,
NJ

Sil3
10-29-2007, 09:44 AM
Thats strange... try to first really disconnect the edges that you marked to make the cuts, instead of only select them, then Unwrap it on Roadkill and see if that still happens.

Brainsells
10-29-2007, 01:21 PM
Maybe something is wrong with the geometry from lightwave?
Try extracting all the polygons on the model, then delete the original. See if that fixes anything.

illusory
10-30-2007, 04:48 AM
Yeah, I extracted the ploygons from the clusters, and now have 3 objects. They all went through roadkill fine, and I was able to adjust the UVs in XSI. Gues when I merge them it will put all the UVs on one map, overlapping.

But maybe this will stilll work for Zbrush, if I only work on one part at a time...?

thanks much,
NJ

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