Please stop overlapping islands in UV unwraps

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Please stop overlapping islands in UV unwraps

Postby chuck_starchaser » Sun Jan 17, 2010 5:34 am

Tried to bake an AO for the Mining Base and it won't work.
Ambient occlusion just barely worked for the Agricultural base.
Now I'm working with the Diplomatic Center, and same thing...

Image

You see what happens? When you overlap islands, the AO's for each of the islands
sharing the same texture space all overwrite one another and mix together chaotically.
This is what it looks like on the model:

Image

So, PLEASE, PLEASE, PLEASE, stop overlapping islands, already!
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Re: Please stop overlapping islands in UV unwraps

Postby nphillips » Sun Jan 17, 2010 4:42 pm

ZUH??

How did the textures work in the first place??? Unless the islands are sharing the SAME texture and are the SAME SHAPE, I don't see any reason why they should be overlapping. That's just bad modeling/texturing, period.
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Re: Please stop overlapping islands in UV unwraps

Postby chuck_starchaser » Sun Jan 17, 2010 5:11 pm

It's a bad habit that comes from the times before ambient occlusion, bent normals, and other bakes. When all you were expected to show on a model was diffuse and specular textures, if you wanted to paint the same pattern on more than one part of the model, you just painted the pattern once and piled a bunch of unwrap islands on top of it. Then again, I don't know how long ago the mining, agricultural and diplomatic bases were textured; but for the past two years I've been saying to people "don't overlap the islands", and I think the only one who's got the message is Deus Siddis. EVERY model I look at has islands piling on top of each other.

I do have some good news for the die-hard mirrorers out there, though. I used to say "no mirroring", but by now all the mirroring issues have been resolved. Normalmaps work fine with it, and even in CineMut, the model-space PRT's were replaced by tangent space bent normals, which are mirror-friendly. So, for perfectly symmetrical models, with identical ambient shadowing on both sides, it is okay to mirror the UV map. Not that it would look too appealing to see the same scratches and dirt and rust marks on both sides of the centerline... But if a band or strip along the center of the ship is unwrapped un-mirrored, and the rest mirrored, it might be a lot harder to notice the mirroring.
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Re: Please stop overlapping islands in UV unwraps

Postby Deus Siddis » Sun Jan 17, 2010 7:42 pm

chuck_starchaser wrote:Then again, I don't know how long ago the mining, agricultural and diplomatic bases were textured; but for the past two years I've been saying to people "don't overlap the islands", and I think the only one who's got the message is Deus Siddis. EVERY model I look at has islands piling on top of each other.


Yeah I learned my lesson with the newer model for the trilaterally-symmetrical derivative interceptor I did a while back. A lot of extra micromanagement of the AO baking process for a result that is not the best.

I do have some good news for the die-hard mirrorers out there, though. I used to say "no mirroring", but by now all the mirroring issues have been resolved. Normalmaps work fine with it, and even in CineMut, the model-space PRT's were replaced by tangent space bent normals, which are mirror-friendly. So, for perfectly symmetrical models, with identical ambient shadowing on both sides, it is okay to mirror the UV map. Not that it would look too appealing to see the same scratches and dirt and rust marks on both sides of the centerline... But if a band or strip along the center of the ship is unwrapped un-mirrored, and the rest mirrored, it might be a lot harder to notice the mirroring.


Very good to know.
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Re: Please stop overlapping islands in UV unwraps

Postby TBeholder » Wed Jan 11, 2012 6:23 am

As a side note: this would have been prevented if instead of reusing textures it was done via reusing subunits (or less-than-complete-subunit ship parts). IMHO.
I mean, there are lots of highly reusable nice things - habitat domes (Mining Base), dock assemblies, big dishes that can eventually be made rotating (Mining Base, Relay), etc.
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Re: Please stop overlapping islands in UV unwraps

Postby klauss » Wed Jan 11, 2012 3:34 pm

I think units already support having more than one mesh in their mesh list. We could work on extending that with the required features, like rotating meshes, and stuff like that.

Meshes aren't subunits, they're just meshes. So units could be made of several meshes, or several instances of the same mesh.

Beware, though, there's a steep overhead on splitting geometry in its own mesh, as rendering each mesh requires a rather expensive API call. To put it in numbers, rendering 10 meshes of 100 tris can be 10 times slower than rendering 1 mesh of 1000. But I agree, there's a lot of reusability potential.
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