Help needed with UVW Unwrapping

Cnc96

Hello all
I am currently working on a 3d model and I have reached the phase where I can now start to texture the model. Unfortunately, I am having trouble getting the UV Unwrap with as little seams as possible? :poly127:

I'd appreciate it if someone could help me/guide me through the process of unwrapping the first part of my model.
There are some screen caps of the entire model attached. The piece which I am having problems with is the front 'nose cone' and I foresee myself having issues with the end section. If any other screen caps are required, I will happily post them.

Many thanks, Jamie

Bek

What've you got so far? Upload your .obj perhaps?

Cnc96

Well, at the moment all I have got is a flat UV by using the flatten mapping tool. It has turned out alright, but in some places like the front nose cone, I think it may be difficult to accurately texture it and line everything up because I was planning on putting a Sharks teeth decal on it? I'll include both the .obj and .max files.

Files: (https://www.dropbox.com/s/sva19nkubkri5ix/Missile%20Files.zip)

WarrenM

There's a balance to be struck with UV unwrapping. Don't worry so much about minimization of seams that it affects your ability to texture the asset nicely, for example. Sometimes eating a few seams in order to get a nice flat unwrap in key areas is worth it when you consider the larger picture.

peanut™

If your getting seams on such of model, forget about them and make something new again. I got really good at unwrapping by spending the whole day unwrapping everything i could get my hands on. And play around in photoshop to fix.

Im talking 20 sec to 1 min on anything.

Bek

Okay, here's some tips. Also you had some weird geo (doubled verts) on your mesh that I cleaned up. Also I deleted 3 of the 4 fins, you can just mirror them back (Once you've finished the UV's—would make sense to have them overlapped / share the same texture to save space). You might also want to bookmark this for further consideration: http://www.polycount.com/forum/showthread.php?t=117017

https://dl.dropboxusercontent.com/u/15050523/missile.obj

I quickly unwrapped your object (but I didn't pack it or optimise it much). Hopefully this will make it easier to understand my next few points.

As WarrenM pointed out UVing involves tradeoffs between seams and distortion. Seams are (generally) bad because they increase vertex count (more on this in a second) and make your asset harder to texture. Know where to place seams is pretty key, especially when it comes to objects that will be normal mapped. So on your missile I added seams where I imagined there would be material breaks and sharp edges, or just to reduce distortion. Distortion can be a bigger problem depending on the texture it will have and the texel density. This is why it's good to know what the final result will be before you begin. If the distortion is too much in one area you might want another seam.

One thing I didn't do (because it's not super easy in modo as it is in max) is straighten UV islands to avoid aliasing. A straight line requires less resolution to appear straight because pixels are square; curved things need more resolution to appear smooth. Straightening can increase distortion but it's usually worth it. Especially if it's something with a low texel density.

So back to seams and vertices. Each vertex can have only one UV co-ord, so what happens when a vertice lies on a UV seam? The one vertice is in two spots. One co ord per vertice, and two co ords, means two verticies. So every vertice on a uv seam is doubled (or tripled). However, verts can also only have one normal. So if you're splitting shading (having a hard edge) then you've got another split—but if you've already split by UV seams (which you have to at some point) these splits don't stack, since the extra vert from the UV split can hold the second normal vector. That's my understanding anyway. So, if you have hard edges where you have UV seams you get those hard edges for free, no extra verts.

Where you have a hard edge you require a uv seam; but a uv seam does not always require a hard edge (but it's free, so unless it's a curved surface, go for it). The first part of this is for normal mapped stuff anyway.

If none of that made sense here's a better explanation:
http://tech-artists.org/wiki/Beveling

that also covers when, using those ideas, you should bevel instead of having another hard edge/uvseam for the most efficient result.

When you get on to packing UV's, consider the best ratio (2:1 might work better for things with lots of long, thing parts, like swords for example), having even texel density (as radically different texel density looks inconsistent and bad), having enough edge padding between islands (so that when the texture drops down in mip-maps islands don't bleed into each other).

Cnc96

Ah ok, I'll look into all of your suggestions to see which one works best for me. But thanks for the help guys, you've been really helpful

WarrenM

peanut™ wrote: »

If your getting seams on such of model, forget about them and make something new again. I got really good at unwrapping by spending the whole day unwrapping everything i could get my hands on. And play around in photoshop to fix.

Im talking 20 sec to 1 min on anything.

I'd like to see some examples of these unwraps. It's usually a few hours for me on each piece because I play tetris for awhile trying to get an optimal use of UV space happening.

peanut™

If you take more than 18 sec for this example, your probably OCD.

WarrenM

Well, tear it up. He's got the OBJ files above. Let's see what you consider done in 18 seconds. :P

peanut™

ZZZZzzzzz

WarrenM

That's what I thought. :P

passerby

really this should take any time at all, can cylindrical unwrap most of it, than just planar the fins and stitch a few things, and done.

theGrandPoobah

This is an interesting thread to me, because I am a beginner to UV/UVW related stuff and am looking for tutorials/literature on better following these processes.

I get the core concept behind unwrapping a mesh and the implications of normal mapping, but the more intimate nature of how to how to build skins, especially for humanoid characters, is still mysterious to me.

Does anyone have any good resources on the subject?

Dethling

For the fins you can simply copy/paste the UV islands, to spare some space.

For the rocket self, I would cut the UV at every smoothing change and then apply a cynlindrical unwrap.
Yes this will cause some streching but if they are visible depends on the way how you texture it later.