What Does a Good UV Map Look Like?

b_beauchamp

Hi everyone, I am updating my portfolio and will be showing UV maps alongside my new models. Are there any general expectations/standards for how good UV maps should look in general? My current model is somewhat organic in shape and the UV map looks weird to me. There are no issues such as texture stretching or overlap, I just don't know if the map "looks bad" or could be better. I don't have much experience making proper UVs so any advice is helpful. I am using Maya. Thanks!

gnoop

a) For a thing without hard edges you have too many UV islands   and  too many redundant support loops in the geometry.  

b)  You could bend your UV islands slightly to be more straight  less curved the way a good packer would pack them a lot more efficient .

oglu

I wont say that there is to much geo. That depends if this object is goin to be displaced and further scultped.
If its a low poly i agree.

b_beauchamp

@gnoop Thank you for the advice! I have reduced the number of UV islands and support loops. This is my low poly model, the total vert count is now 8,256 (down from 14k). I am fairly new to Maya and don't know a good method for gently straightening the islands. The "Straighten UVs" tool creates rigid rectangles and deforms the internal edges. What would you suggest? 

Alex_J

https://www.youtube.com/watch?v=s_KLbTUdKms

this video shows good overview of most the tools you'll use

b_beauchamp

@Alex Javor Thank you for sharing that video. It was really helpful. I'm feeling a lot better about my UVs. Are they in a good place now or are there other things I should work on? 

Alex_J

other guys can answer better than i can for stuff like that, but the best way to know if you got good UV's is to start texturing. If there is issues it will become apparent fast, and also you might learn how much "bad" practice you can get away with depending on the asset and it's use. Build up the experience and then it's easier to make judgement calls in the future.

Eric Chadwick

Your object is symmetrical. Does the texture absolutely need to be different on both sides? (most people don't notice texture reuse on sides of things, since you can only see one side at a time!)

You can overlap shells to save significant space. A key skill for a game artist.

You can also use non-square textures. As long as they're powers-of-two in dimensions.

More tips here
http://wiki.polycount.com/wiki/Uv#UV_Tutorials_.26_Threads

gnoop

Imo it's better but  still  looks like a hell lot of redundant polygons for real time considering almost no small geometry details at all.     I bet if decimating it twice  there wouldn't be much of visible  difference.    And yet the islands could be slightly bent  with a minimal stretching price.   Isn't MAya has something like "pins"  from Blender or MAx? I recall "Roadkill" plugin  did so (a clone of Blender UV for MAya).    I myself opened MAya  decade ago last time. 

 

amoeba

I'm very curious about best UV practises. I wish there was a thread here for general UV tips like the giant topology thread and normal baking thread.

Often I wonder if I'm unwrapping things inefficiently when I end up splitting things to minimize stretching but raising the vertex count in-engine. It seems like a balance between some stretching/distortion or vertex count. In other cases splitting a UV island up allows you to pack it more efficiently to increase texel density so that can be another variable. 

I generally split my maps always at 90° angles when the mesh has those but it gets a bit muddier where/how to split on more complex organic shapes such as hands/fingers.
 Should each finger have their own island if the hand ends up unwrapping with bent fingers like this if it gives less distortion by splitting it up? 

Should both sides of the hand be connected or keeping each side a sepearate island? Keeping it as one sometimes gives me ugly areas. 

Packing is a bit easier as well with it split up as I can give the inner side of the hand less texel density for example if that is rarely seen.

The screenshots above aren't mine and might be bad examples.

Sometimes when I unwrap a part of a organic shape, various limbs etc will point out such as here, I've wondered if these should be cut off for nicer packing.

Another example of something which could perhaps be packed better by splitting it up?

b_beauchamp

@Eric Chadwick Thank you for the advice. I've spent these past few days trying to make my UVs perfect. I stacked the shells and tried to pack them closely. If I made another cut through the longer pieces and straightened the shells I think I would be able to pack them closer and get a higher texel density, but I don't want to make unnecessary cuts and get bad stretching. Finding a balance between the number of cuts, stretching, straightening, and packing has been difficult. I have decided to shelve this particular project, but I learned a lot from working on it so that's something. 

b_beauchamp

@amoeba I started out looking for advice on UVs but there doesn't seem to be any definitive resource on it. If I cut my islands into nice rectangle shaped pieces I could make a densely packed map at the cost of more cuts. I don't know which I should prioritize. 

sprunghunt

b_beauchamp said:

@amoeba I started out looking for advice on UVs but there doesn't seem to be any definitive resource on it. If I cut my islands into nice rectangle shaped pieces I could make a densely packed map at the cost of more cuts. I don't know which I should prioritize. 

Fewer cuts is usually better. It's often better to have a bit of distortion rather than have lots of UV cuts. UV seams are always a little visible even with modern tools but you can compensate for distortion. 

What you have in the final image looks ok though. I'd try and find something to put in the hole in the bottom right. For environment assets I will often add extra geometry just to fill out a UV map.

For example: you could create some vertebrae or a lower jaw for your skull and put the UV for that in the hole. 

Eric Chadwick

We could start to compile a list of rules. But there are always exceptions. It usually comes down to experience.

First I try to split the model along likely seams, and Relax/Pelt those. If there's still distortion, I'll cut a few more seams. If there are peninsulas sticking out that make packing difficult, I'll cut those off. Straightening at the expense of distortion, that's a judgement call... if there are likely to be LODs, and/or hand-painted details, then the straighter the better.

Increasing the vertex count through more splits is not as much an issue anymore, at least for desktop games. For mobile though, yes, still an issue.

Don't forget that you're not limited to square layouts. Rectangles are often better (as long as you stick with powers of two dimensions you'll be ok)

My earlier wiki link has some good workflow / thought-process tips.

b_beauchamp

Thank you all for the advice. I feel like I have a better understanding of good UV practice now, and I look forward to applying it in my current project. I will be sure to check out the wiki when I get to the UVs again.