Is UV seams should be avoid as much as possible?

vempdance

If I don't care about vertex count and I make texture map in substance painter that has tri-plane projection, is there any reason that I need to avoid UV seams as much as possible?

And by the way,is UVs need to be flattened as much as possible if I use substance painter and have enough resolution for the map?

Thanks.

JordanN

I would do my best to hide them.

The problem with UV seams is they can cause textures to look ugly, because it shows were a texture begins and ends instead of just keeping everything ambiguous. I don't know how substance painter handles it, but I imagine it's the same thing unless you can "paint out" those areas.

vempdance

JordanN said:

I would do my best to hide them.

The problem with UV seams is they can cause textures to look ugly, because it shows were a texture begins and ends instead of just keeping everything ambiguous. I don't know how substance painter handles it, but I imagine it's the same thing unless you can "paint out" those areas.

Thanks for the reply.
In fact when baking normal map, separating UV shells (which means UV seams) at the right place will give better result rather than trying to hide them.Substance painter's tri-plane projection could make seams unrecognizable.And of course as you say,It could also paint out those seams.

So I really found that it may be not necessary to avoid UV seams(or hide them)with nowadays texture working flow.But in case for something that I may not notice,I asked the question here.       

RobeOmega

JordanN said:

I would do my best to hide them.

The problem with UV seams is they can cause textures to look ugly, because it shows were a texture begins and ends instead of just keeping everything ambiguous. I don't know how substance painter handles it, but I imagine it's the same thing unless you can "paint out" those areas.

I just set it to Triplanar mapping in Substance Painter so it is very rare I get any kind of seam visible in work I do in SP.

CharacterCarl

As far as I know, each UV island means an additional draw call. So, keeping them down will help with performance (I don't know by which margin though). An unreasonably high amount of UV shells also means that you will waste texture space on edge padding depending on the size of the texture.
Bear in mind as well that tri-planar projection doesn't lend itself well to all purposes: Imagine having a sign on a piece of metal perhaps in a software other than Substance and then having to cut and piece together the individual parts to change it. Also, axis-aligned UVs (for cables for example) obviously don't work  with tri-planar when the actual mesh is not axis-aligned (but deformed/curved).

musashidan

Also, tri- planar isn't ideal for all situations and is not suitable for specific patterns. Plus, I'm not sure if they've fixed the seam mask T-P bug in SP2? Although the addition of a clone brush (finally) makes life a lot easier.

JedTheKrampus

DerRazputin said:

As far as I know, each UV island means an additional draw call.

This isn't correct. UV islands don't mean additional draw calls, but they do mean that the vertices are duplicated along the seam unless you use an unorthodox method for indexing vertices. You might also lose a bit of cache coherency on the GPU if you have too many UV islands, but you have to get to a point where you're seriously losing texel density to padding for that to happen. You only need more draw calls if your mesh has more material slots.

OP, my rule of thumb is that you should have as few UV seams as you need to have a low-distortion unwrap, so long as that also means your UVs are reasonably easy to paint on. This means that you lose less texels to padding and avoid as much vertex duplication along the seam as possible. Texels which are used for padding are all texels that aren't making your art look better, so you should have as few as possible as long as that number of seams also facilitates tight packing. Usually aim for 12-40 big islands depending on the asset and you should be fine.

myart1372

what if we want to hand paint those textures on 3d model (not 2d uv) in some softwares like mari , not traditionally with photoshop ... in that way is it important how many seams we have ?

poopipe

You should...
Hide  seams where possible 
Put seams  where they are required for normal baking
Avoid angled seams where practical (to minimise aliasing artefacts)
Leave sufficient padding to prevent artefacts caused by mip-mapping

More importantly, test your unwrap in engine before committing loads of work to texturing - that way you'll be able to see which bits aren't working right