High-Poly Hard Surface UV Mapping?

#1

Hi there,

   There are literally no "High-Poly Hard Surface UV Mapping" tutorials on the Internet, at all. I've searched for days but can't find a single one. So thereby, I kindly need you guys' help.
   
   So I have this M16A4 model, which can be seen here: [http://forums.cgsociety.org/showpost.php?p=7290053&postcount=25](http://forums.cgsociety.org/showpost.php?p=7290053&postcount=25)

This is all made in 3ds Max. Now, I want to texture (paint) this by using Mudbox. I have no experience on how to do this, and as I've been saying, I don't know where to find any tutorials. So my initial attempt was to try learning it myself, which failed. I'm not talking about painting the gun, but to get the UVs right.
   
   Basically what I've tried is creating the seems like this (let's take the Stock Pad for now):
   
   [img]http://img220.imageshack.us/img220/7475/stockpadseams.jpg[/img]
   
   As you can see, I have created seams at point 1, which goes from top to bottom of the model. Point 2 is just a circle seam to cut out point 3's polys, which is the front of the stock pad. And me being an idiot, I skipped unwrapping the inner parts  because "they're never gonna be seen" in my renders. You can see this at  point 5.
   
   I'm not sure if I should unwrap the high-poly (TurboSmooth'ed version) or the low-poly one (not TurboSmooth'ed). This was done with the high-poly version, and it lags like mad when working with the unwrapping. But if I unwrap the low-poly version, it's stretching the textures at the uv edges.
   
   And by the way, how are the texture supposed to "weld together" the seams? Because as you can see here, it's clipping between the edges because the parts are not at the same spot in the UV map:
   
   [img]http://img802.imageshack.us/img802/9131/stockpaduvmap.jpg[/img]


   This is with the texture applied. You can see where the edges/seams are because of that texture bug:
   
   [img]http://img577.imageshack.us/img577/4236/stockpadtexture.jpg[/img]
   
   For testing purposes, I've tried Roadkill, Unwrella and XRayUnwrap to unwrap the "potential" seams I've created. None of them have made it more clear to me.
  
  This is a wireframe of the model. Both high- and low-poly:
  
  [img]http://img707.imageshack.us/img707/7356/stockpadwires.jpg[/img]
   
   I think my model is worth being textured, and it's so annoying to have the knowledge of modeling high-poly, but not knowing anything about texturing...
   
   So please, anyone, help me out of this painful cage.
 
 
 Thanks in advance,
 Gnasty
#2

The UVs look decent, although I would have probably UV’d the base-mesh.

The problem looks like the UVs aren’t being smoothed/subdivided at render time the same way as the geometry is. I’m not familiar with Max, so I’m not sure what options you have available for smoothing or not smoothing UVs at render time. Different applications use different rules for subdividing of UVs - all-hard, all-smooth, hard-borders, hard-corners - and only a few 3D applications provide options to handle all of these rules…

Basically the idea is to pick a UV subdivision method and stick with it. I personally prefer hard-corners or smooth-all, in Maya (or UVlayout) I’ll UV the base-mesh until the UVs look good - I then subdivide the geometry 2-3 times using either Cyslice (which is the only modelling application I’m aware of which can do hard-corners - the default used by PRMan/3Delight) or Maya (which can do everything bar hard-corners). I then export this subdivided geometry for painting in Mari (Mari can’t subdivide geometry). This way I know I’m painting on geometry and most-importantly UVs which very closely matches the final rendered geo.

As far as I’m aware Mudbox offers three options for subdividing UVs - all-hard, all-smooth (via an environment variable change) and hard-borders.

I hope that makes sense.

#3

Thanks, earlyworm. I think everything’s getting more clearer to me now. But there’s still one thing left. I’ve heard about this UV Smoothing. TurboSmooth is always smoothing my UVs, making them stretch at the UV edges. Is there an option, anywhere, where I can tick this UV Smoothing option off? Or is there a work around of some sort? That’s, what I can think of now, the only thing I need to know.

I got to know XRayUnwrap a bit more yesterday and I'm slowly getting more accurate UVs. But still a lot to learn.

By the way, what is the best technique to unwrap hard surfaces? I mean like, I’ve tried split everything up so each corner of, say a box, is being split, plus the top of it. So when unwrapping, it would look like a “roadkilled” animal. I guess that’s what you’re supposed to do, but I’m not entirely sure… I will post a screenshot of my latest UV map later today.

#4

Best way to describe what’s going on is with images. This describes some of the main ways in which you can subdivide UVs (geo on left, uv’s on right). In order after the base mesh the various rules of subdivision are…

[ul]
[li]Smooth All UVs. This results in little to no distortion.[/li][li]Smooth Internal UVs, Hard Border UVs. Pretty good with regards to distortion apart from in the corners of the object - on soft-surface models like creatures and characters (which don’t have corners or hard edges) this method works pretty well. This is the default used by Mudbox and Zbrush.[/li][li]No smoothing of UVs. Also known as Linear UVs. Lot’s of distortion, primarily in areas with tight edges. You can get away with this method if you subdivide the model once and then reflatten/unwrap the UVs to remove the distortion (although doing this obviously increases the poly count).[/li][li]Smooth All UVs, Smooth Internal Map Edges. Smooth All works well until you have internal map edges. Then it falls apart.[/li][li]Smooth All UVs, Hard Internal Map Edges. This keeps the internal map edges hard so you don’t have crazy distortion issues.[/li][li]Smooth All UVs, Hard Corners. This is the default method used by Renderman (PRMan and 3Delight). This results in little to no distortion, but you’ll notice it’s also altered the geometry as well (this can trip modellers up).[/li][/ul]On top of this, you’ve got to consider that all software packages seem to use different smoothing algorithms (there, so even if they do use the same subdivision rules - the resulting position of the CVs or UVs might be off in various places.

Hope that’s of some help.

#5

Sadly, the methods max use to smooth meshes are pretty much incompatible with all the other methods out there. That’s one reason people (including myself) are asking for the addition of full Catmull Clark subdivision surfaces in max on the autodesk wishlist, so that you can move your mesh to programs like mudbox, and then get the same subdivision when you bring it back to max. If you do a search in the max section of cgtalk, you’ll find plenty of threads discussing the problems with turbosmooth messing with their mapping.

Personally, I avoid using unwrapped uvs for my hard surface stuff, I mostly use techniques like Blended Boxmaps and projection mapping, which apply your paint onto the highres smoothed mesh. You can read about them here:

http://www.neilblevins.com/cg_education/cg_education.htm

Hope that helps.

  • Neil
#6

Thanks both of you :slight_smile:

   [b]soulburn[/b][b]3d[/b]
  Now that's an interesting technique! I will definitely try it out, thanks!

EDIT: Hmm… That means I cannot paint in Mudbox though. Because it’s using 3 different channels, right?

#7

Well if you’re trying to paint in Mudbox, it really doesn’t matter how your UVs are laid out, so long as they are proportional and clean in relation to each other. That is: a quick AutoUV would do the job just fine.

It seems like you’re only using Mudbox to paint the mesh, right? In which case you don’t need neat, paintable-in-Photoshop UVs at all. If you’re not subdividing or sculpting in Mud, just use it as a paint station! Piece of cake.

Since it’s a personal project and not part of a gaming/work pipeline, and nobody else will be trying to paint using your UVs, it shouldn’t matter so long as they’re proportional. Mudbox won’t care. I paint on tons of poorly-UV’d high-poly meshes in Mud - and if you’re not extracting normal or displacement maps or sculpting, it really doesn’t matter how your UVs are.

#8

InfernalDarkness
Yeah that’s exactly it. I’m using Mudbox for painting only - a paint station as you say!

This is a test I've done. It's made by just unwrapping like normal. Had a  few texture distortions at the edges, but hid them with some blur and  stuff. Is that a valid way of compensating texture bugs?
 
 [img]http://img825.imageshack.us/img825/6280/magazineuvmap.jpg[/img]
 [img]http://img268.imageshack.us/img268/3922/magazinetexture.jpg[/img]
 
 
 Ended up like this. Remember it's just a test texture and does obviously  not represent final work, so don't mind the incorrect scratches please:
 
 [img]http://img171.imageshack.us/img171/1748/camera04.jpg[/img]

So in overall, does the texture seem fine? Can you see any errors UV-wise in the render above?

#9

Your texture on the magazine looks fine. If it’s just for a personal project and your happy with the results then go with it.

Projection painting (in Mudbox, Mari, et al) hides a lot of sins when it comes to texture painting - it’ll often look rubbish and distorted in the texture map which may make 2d painting or editing difficult, but it’ll look fine when applied to the geometry.

When it comes to unwrapping hard-surface UVs I try to keep things fairly planar. How you’ve done the UVs in your first post is probably how I’d cut them up. With the gun magazine I’d probably cut it up further into 5 different sides (front, left, back, right, bottom) if trying to get it into one or two shells proved difficult.

#10

Thanks for your help all, and especially you earlyworm for clearing things out! I’ve learned a lot of you and I am progressively getting to know everything much better now.

#11

Inserting edge loops will also lock down the UV seams on the sharp corners. I use Mari/Mudbox, but if you get these distortions, the safest solution is UVing at a higher subdivision.

#12

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