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JadeRode

Preferred UV Unwrapping Method

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Hello everyone! Jade here. I am here wondering: How do all of you 3D artists out there UV unwrap your 3D models? I am asking as I have started working towards making my own game, and I've made a few pieces of furniture, and, every time I get to the unwrapping stage, I get stuck thinking about how best to unwrap the model.

So far, I have come up with these key elements to consider when unwrapping:
- Space (between islands and the borders)
- Overlapping UV Islands
- Scale
- Location

What I have been doing is, after making sure my model is in the appropriate position, I apply the new scale, rotation, and location, so the defaults are 1.0, (0,0,0), (0,0,0). Then I unwrap the models making sure each island is understandable and has its own spot on the map (each leg of a chair, each panel of a shelf, ect.) and that I use as much of the space as I can, trying not to break scale uniformity. If I need to scale any one thing to get things to fit, I make sure I scale everything, so the scale ratio of the UV maps is 1:1, or as close to 1:1 as I can get it. I also make sure there is at least 8 pixels of space between everything, in relation to a UV map placed on a 256x256 image texture.

What is really bugging me with this is, as ideal as letting each face have its own unique texture spot is, I know it would drastically cut down on work, in terms of trying to draw on textures, if I overlap the UV Maps (overlap each leg of a chair on top of each other, cut a shelf in half and stack the halves, ect.).

Where do you guys draw the line? Do you favor productivity or the uniqueness of each model more? Is there a great visual difference, in your opinion, of models that have identical textures on its different faces vs models that have faces that are all unique?

Any and all thoughts are appreciated! Thank you all for reading!

TL;DR: Describe personal UV Unwrapping workflow. Overlap identical UV Islands, or don't overlap anything?


-Jade

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3 hours ago, JadeRode said:

Overlap identical UV Islands, or don't overlap anything?

If you share textures for multiple models or at least instances of them, then you can overlap islands as well. Both leads to the same repetition of textures, but helps with memory requirements and cache utilization.

To say it differently, i could also ask: "I have 6 chairs around the table. Is it ok each chair looks exactly like the other?" There is not much difference between this and asking: "Is it ok each leg of the chair looks the same?".

The only game that did not do any repetition at all was Rage IIRC, leading to low texture resolution.

So very likely you want to use overlaps. Mostly in cases where the patterns look uniform, like wood, concrete, etc. The more distinguishable a part of texture is (e.g. graffiti on a wall), the more you want to avoid reusing it, or you try to distribute these parts more coarsely.

It also depends on the geometry of the environment. If the untextured level already is distinguishable you can reuse texture much more likely. If the level looks similar no matter in what direction you look, then you might want to help this with differing texture or colors.

Finally you can reuse high frequency textures (grass, wood) more easily than low frequency (bricks, rocks) without visible repetition.

 

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The method you use for texturing / uvmapping will to a large extent be governed by the game / engine / tech that you are producing the models for. Different games may have different art pipelines, and different pipelines for:

  • Animated characters
  • Dynamic game objects
  • Static environmental art

A large distinction is between an engine that requires uniquely uv mapped triangles (call it 'method A') (or mostly, there may be some leeway for mirroring in models), and one that does not ('method B'). B used in engine is more likely to be seen in environmental art, primarily for efficiency purposes, and is probably less used today than in the past, as texture memory etc has increased.

Method A unique uv mapping per triangle allows things like ambient occlusion, and normal mapping. Often the same uv mapping is used for textures (albedo, metal / roughness etc) and for normal maps / ambient occlusion etc, but an engine could use use 2 or more different uv mappings for the different channels.

Some texturing tools are designed to work with unique UVs (substance painter, mari, texture painting in general), and some work fine with overlapping UVs and multiple materials (e.g. modelling tools such as blender / maya). Organic models lend themselves to texture painting well, whereas inorganic models can also be textured easily using the overlapping UVs approach (B).

And, you can also combine the two. You might, for example, texture a chair using method B, then use your modelling package to bake this down to a unique uv map (A), with normal maps and ambient occlusion.

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You guys have both said some very insightful things, and I'm convinced you guys have been doing this for a while. Thank you guys for your input! I have been swayed to start over lapping my UV Maps in most cases!

 

This is a photo of a shelf I UV unwrapped. I bet its glaringly obvious where I can stack and pack.

JadeSilkShelf005LOD0UVMap.png

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If you want to use overlapped UVs in this way (I suspect you mean uv map a table leg for example, then duplicate the leg 3x and use identical mapping, and just draw the texture once) you can still use it with unique uvmapping in the future, by baking it down. I would highly suggest you experiment with baking, it will open up many more options, e.g.:

 

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Just to add to this, you can use overlapping UVs but if you're going to bake make sure you take all the overlapping ones and offset them to the next UV space. Once your bake is done you can reverse the offset and you'll be fine. If you bake with overlapping UVs you will not normally get a clean bake.

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Ah, I forgot that multiple UV maps is a thing. Thank you, @lawnjelly, for the tips on multiple UV maps.

I definitely need to experiment with baking more, because I see the great value in bakes. I have done some bakes, mainly normal map bakes from high poly models to low poly ones, but it is still incredibly foreign to me and I only seem to get it to work half the time.

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It is well worth looking into. I normally work High Poly to Low so baking is required. I also bake Low on Low to generate certain maps I need. Making a full baking tutorial is something on my list of things to do in the near future. On another forum I've spent a lot of time helping other 3D artists bake out their maps and correct baking errors. There are a lot of things to learn, and tricks to help reduce errors.

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1 hour ago, JadeRode said:

@Rutin When you make your tutorial, you should definitely give me a hollar! I would watch it and learn! XD

Until then if you have something you need looked at just let me know and I'll see if I can help. Feel free to PM me if you need assistance.

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