Can I Bake UV Shell IDs into the alpha of a position map?

parsaiej · Oct 2016

Hi there,

I really need a way of storing UV Shell IDs into a map channel. Can it be done, in any software at all? Is there a way for me to write a tool that allows me to do this myself? Thank you!

Never posted here before, and I know very little about 3D software- strictly a graphics engineer, so apologies in advance for missing anything obvious.

Eric Chadwick · Oct 2016

What exactly do you mean by UV Shell IDs? An image or two would help immensely, as well as a use case.

parsaiej · Oct 2016

I'm working on a game in which you play as a tattoo on human skin. It calls for a lot of interesting work with UVs.

The picture refers to what I mean by the UV edge, the link goes to a gif showing my issue in action: https://twitter.com/parsaiej/status/786039071873183744

throttlekitty · Oct 2016

That's fun! For a Shell ID, you could assign a colored material or grayscale value to each set of faces in that UV shell in any 3d app, and bake them to a texture there or in xNormal. It's common to bake out a Material ID for masking purposes during texturing. You didn't mention the UV edge part in the first post, but that sounds more like a code solution than an art one- though an object space normal map may be of help there.

parsaiej · Oct 2016

Yup, I was planning to bake the ID into the alpha of an object space position map

Thanks for your help! I'll check that out. So far it has been a heavy use of coding + compute shaders to get the tech working.

Eric Chadwick · Oct 2016

I think what you want is decal projection mapping. Here's an example in the game Trackmania 2, skip to around 2:10

parsaiej · Oct 2016

I plan to integrate this solution with screen-space decals. The big thing is I need to properly transform dynamic positions withing the UV frame, and ensure that those positions are mapping to the correct UV shells.

Once the positions are properly transformed, I would render the actual tattoos as decals based on those positions.

Eric Chadwick · Oct 2016

If you web search for "decal projection mapping" you should find the Wolfire blog and a few other gems, different approaches for similar situations.

parsaiej · Oct 2016

Yep I was researching that the other day, I plan on using Wolfire's solution since it works really well with a singular set of geometry.

My unique constraint is the fact that a player moving through UV shells poses a challenge that decals cannot on their own solve, and must be solved in the inverse approach.

Can I Bake UV Shell IDs into the alpha of a position map?

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