UV'ing low poly models

Tom Ellis

Hey there everyone, I got a question about UV'ing characters, specifically for low poly, but I guess it would apply to any model which needs to utilize a lot of mirroring etc.

So I made my first low poly character today, I would post the flats but they're on my other computer. I went to unwrap it, with the intention of using a 256 or 128 map, and planned to do the common unwrap you see where the face is mirrored and has a dead straight line down the centre. But I couldn't for the life of me get it unwrapped well that way. I ended up just doing a seam down the back of the head + pelt kinda unwrap.

Does anyone know of any tuts or tips on how to unwrap this way, It looks a lot easier than it it!

I have more trouble unwrapping a 400 tri model making decent use of UV space than I do with a 4000 tri character!

Thanks

fade1

of course a screen of your char would help.
if you have a seam, maybe you have some mipmapping artifacts there. if you set your viewport prefs to unfilitered things shold be alright. but this is just a guess...

Tom Ellis

I know I shoulda really posted wires/flats, I may do tomorrow when I'm back at my other PC.

I guess I'm asking more about how to unwrap, like should I use pelt map for the head if I'm mirroring it?

My guess was that you unwrap the head, delete half of it and then mirror it so the UV's are on top of each other, but while this does produce perfectly overlapping UVs, the pelt map doesn't really work out so great, like I don't have that perfectly straight edge along my symmetry line. Should I use a different mapping projection?

Thanks

MoP

Get your straight edge in the middle first, then use Relax on the rest. It will use the centre line as a basis for relaxing. Just don't relax (or pelt) the whole UV element.

Calabi

I though it was the other way round.

When I do it I delete half the model do the UVs for that half, then mirror it. I doubt you would automatically get straight line with any tools you have to manually push them that way.

MoP

mopUVLineRelax maxscript...

Tom Ellis

Many thanks MoP,

that's the trick I was missing then, relaxing only part of the shell.

Thanks for the script too, how does it work? (havnt got access to Max on this comp).

MoP

Run it once, and it'll add a hotkeyable or quad menu-able command into the Customize UI window. I put it in the Unwrap UVW quad menu for ease of access. Look for MoP's Tools category, UV Line Relax is the name of the command.

hijak

well i would usually just pelt the head, then delete the half i dont need. That way i get the shape im looking for. Cause i get what your saying unwrapping it as a half does not yeild the results you looking for, thats why i say do it like a whole head and delete half after then just layout the shells. But like i don't even see why do it in maya, id just drop it into UV layout its about a million times faster.

and why have to mirror uvs once you delete half the geo you can jsut mirror the geo and the uvs will be stacked for you as both peices use the same uvs. Way easier imo.

fade1

for very lowpoly chars i usually prefer cylindrical projections and just tweek some uv's here and there. pelted stuff is really hard to paint on, when you're very lowres like 128.

renderhjs

If you are a 3dsmax user (version 9+) you can check out TexTools which is a bunch of scripts in 1 toolbar. Anyway in TexTools there is a symmetry tool that mirrors either one side to the other one (select half of the faces to mirror) or just select the edge mirror and average booth sides.
It works like this:


Just make sure one half looks good (relax some parts, tweak some by hand and rectify some edges so you don't get distorted pixels later) and once done simply select that half using face selection and simply mirror it to the other side.

Another tool in TexTools (added in 3.1) is a snap to pixels button which will snap your selection (edge, verts or faces) in the UVunwrap editor to pixel boundaries. Its used like this:

The button for this is located on the Selection Transform Bar that pops up if you open the UVunwrap editor from the TexTools Toolbar. This tool is useful for very low texture work where snapping to pixel size really matters.


Also I would suggest working in a square UV size and once done with your 2:1 half just use the UVW xForm to extend it or simply use the recently added UV canvas tool in TexTools 3.2

Which just uses the xForm UVW modifier but does the math for you so you don't need to dig with reversed axis, 0-1 ranges and alike things.

Zelenkov

I know you guys are using max, but I have a question. Like, in max say ur mirroring a character head. u would delete half of the uvs for one of the sides, then mirrow the mesh, weld it and set the uv space in W +1, so its occupying the same uv space but only on top of it. So, how would you do this in maya, since maya has no W?

Tom Ellis

You don't need to use any of the area outside of the usual 0-1.

When you mirror the geometry, if you've unwrapped the UVs already then the duplicated geometry will already have the same UVs. They will be right on top of the originals though so unless you have Mayas shade UVs on then you won't see it.

So the UVs are now 'mirrored' because you'll be painting the exact same thing on both UV shells but because one is overlapping and flipped, it'll appear as the mirrored image on your geometry.

It's difficult to explain but basically just unwrap the geometry in question (usually you'll get cleaner UVs if you unwrap before deleting half the mesh).

Delete half the mesh, and mirror it, then weld along the seam, done.

If you want to check it's properly UVd, click one of the verts on the UV shell (don't drag select otherwise you'll select the one underneath too) then ctrl-click - to UV shell, and move it a bit and you'll see you have an exact same shell underneath. Obviously undo after though so they stay perfectly aligned.

Eric Chadwick

Moving the mirrored UVs is necessary however if you're going to bake maps, like AO or a normal map. More here.

funshark

Zelenkov wrote: »

I know you guys are using max, but I have a question. Like, in max say ur mirroring a character head. u would delete half of the uvs for one of the sides, then mirrow the mesh, weld it and set the uv space in W +1, so its occupying the same uv space but only on top of it. So, how would you do this in maya, since maya has no W?

Why do you want to use W since there is only U & V ?

Ghostscape

funshark wrote: »

Why do you want to use W since there is only U & V ?

Little known fact - the UV baker bakes to the 0-1 space, to whatever is highest (most W). So if you've got overlapping, you can avoid the weird rendering issues by increasing the W amount on one of the mirrors.

This is also handy if you're overlapping UVs, like say you have a small bit that you want to have sitting in a black spot underneath some floating geo - just take your tiny piece and increase the W and you'll get a clean render.

Eric Chadwick

W is a third texture coord in Max, used for 3D procedural textures and for storing vertex color in UV channels (need 3 axes for RGB).

You can avoid bake problems if you move the overlapped UVs to -1 on W. Same as moving them on U or V.

Except W can be messy... it's generally hidden unless you purposefully look for it (bad for team work), doesn't get preserved on export to other apps, and high W values can prevent selecting and/or welding UVs. Better to move on U or V.