I need to understand more about topology and UV's

xan11

Hi, i'm new to this forum and also a beginner in Maya. I've been trying to learn how to UV and retopologize these past few weeks by reading websites and watching some free tutorials on Youtube, but I still have a lot of questions regarding what makes a good topology and UV mapping.

My questions are:

-Why do we not cut every face on the UV's so all of the UV's are 'white' (not pinching/stretching)? If we do this, would it affect or deform the model during rigging, animating, etc.?

-Why do some models use triangulated squares? I've heard that it would make each of the polys bigger (therefore easier/faster to control) but with higher resolution? Is that true? If so, then is it ok to use it rather than square polys? And does it work for animated characters?

-What is a good UV seam and is there a type of seam that always works to minimize stretching/pinching in models? Is it ok to use any kinds of seams as long as it doesn't stretch the UV's and can still display decent looking textures?

-Here's a simple model that I worked on recently, I made it in Zbrush before importing it into Maya and retopologizing it. (the shape of the star is based on a 2d artwork by ohn0se on instagram). The ones I show are the retopology results.

1.First result: I can add a decent-looking texture on this one, however I cannot insert a clean edgeloop (maybe because the poly flow is not that great/neat)

2.Second result: I can add clean edgeloops in this one but I have yet to create the UV's.

As shown in my first result, I made a model that is not easy to insert edgeloops as the 2nd one, is this okay as long as it doesn't affect the texture? If it's not okay, then why?

Are the UV's and seams I created okay? How can I improve them?

I used bigger polygons for the first result, is it alright or is it better to use more square-shaped polys like the second one but have more amount of polys?

-If I wanted to create the eyes and mouth as flat surfaces (as I did in my model), is it necessary to make the polys follow the flow/circle of the eye/mouth as I did in my model?

-Are there any principles to making low poly topology for an animated character? (Other than reducing the amount of polys used for faster workflow and adding creases for bendy parts)

Those are all the questions I have for now. I might ask more later if new questions come up. Thank you!

jgarrison

"-Why do we not cut every face on the UV's so all of the UV's are 'white' (not pinching/stretching)? If we do this, would it affect or deform the model during rigging, animating, etc.?"

If you are talking about making every polygon its own UV island or similar, I have tried doing it this way before. I would not do it again in the future because 1. while you could possibly transfer vertex color or use a material program like Substance and get the desired result, the material would be impossible to edit manually in Photoshop (for example) and you would only be able to use tri-planar projection, projecting a material in UV space would get unusable results. And 2. Any kind of LOD shenanigans in a game engine or the like, or a reduction in size or compression of the texture file will make seams more noticeable. I feel that the art of UV unwrapping is finding a compromise between seams and stretching that is least noticeable and easiest to work with.

"-Why do some models use triangulated squares? I've heard that it would make each of the polys bigger (therefore easier/faster to control) but with higher resolution? Is that true? If so, then is it ok to use it rather than square polys? And does it work for animated characters?"

I do not know about triangles affecting resolution. Many people will avoid using triangles if possible because they can be harder to work with in the long run, may affect subdivision negatively, may cause issues when it comes to rigging and animating, and they can disrupt edge flow. With that said, cleaning up triangles can sometimes be more effort than it's worth. Sometimes it's a matter of personal preference.

Regarding your screenshots, I would personally just have a single seam along the center-most edgeloop at the widest part of the star, for two UV islands and call it a day. There could be some minor stretching on the sides but it shouldn't be noticeable.

-I used bigger polygons for the first result, is it alright or is it better to use more square-shaped polys like the second one but have more amount of polys?

Are you trying to do real-time 3D, like for a game? If so ideally you would make a high-poly version with as much geometry as you need to achieve the desired details, and then a Low-poly version with just enough geometry so that the silhouette looks the same as the high poly model from any angle and at the distance you expect the viewer to be seeing it from. Then you would bake the detail from the high-poly version onto a normal map. If the model is going to be rigged and animated, you also need to have enough geometry for it to deform correctly, but for a solid object (Like a car, or a building, or a soda can, or a soccer ball, etc...) only the silhouette really matters.

-If I wanted to create the eyes and mouth as flat surfaces (as I did in my model), is it necessary to make the polys follow the flow/circle of the eye/mouth as I did in my model?

I'm looking at ohn0se's instagram account, and for that character design there are a few ways you could approach the face that would make the topology irrelevant:

1. You could make the eyes, nose, and/or mouth out of tubes, animate them with blendshapes, and switch to a different model when a dramatically different expression is needed. (For example, one mouth model for smiling or frowning, and another for any kind of open mouthed expression.)
2. You could simply draw the eyes, nose, and/or mouth onto a transparent texture file, and then apply that to some subdivided planes placed immediately in front of where the mouth etc would be on the model. Example.
3. If you want the mouth to have an interior then you would need to have edge flow on the model itself to support that. But you could still make the eyes or nose in either of the ways described above, so you only have to worry about the mouth.

-Are there any principles to making low poly topology for an animated character? (Other than reducing the amount of polys used for faster workflow and adding creases for bendy parts)

Having consistent edge loops will make the rigging process a lot easier. If you're talking about a VERY low poly model, like PS1/N64 era, it's often better to make the model out of entirely separate parts, like a doll, to avoid deformation issues. For the model you are making (?) I would think only the arms and legs would need to be deformable, maybe the feet as well. Or maybe you would want the main body of the star to be able to twist and bend, say while it is looking to the side or up and down, but I think the topology you have now would already support that.

Also, if you want to give the character an outline like he has in her art, check out this video: https://www.youtube.com/watch?v=awHQ7KNvI2w&ab_channel=BudgetMelodies

Tiles

Hi,

Proper UV mapping all starts with proper modeling and topology. And the process of UV mapping is simply to cteate UV islands that has the least stretch while keeping the UV Patches as big as possible to keep the number of seams as small as possible.

Think of it like a cutting pattern for a trouser or a t-shirt. Have a look at how the seams are cut in reality. You will not cut a trouser or a t-shirt into a thousand pieces for sure. But you cannot make it out of one piece neither. You stitch several pieces together that makes your trouser or your t-shirt then. And you will not set the seam at a place where it is very visible.

And this is also the art of UV mapping. The rest comes with more experience.

Kind regards

Tiles

xan11

Thank you all for the valuable replies 💜 I learned a lot from them and i'll make sure to practice more with your advices in mind.