Advice when baking thin strips

DustyShinigami

Hi

This is something I've had problems with for a while now. It was great when I discovered the Unitize tool under Modify, in Maya's UV Editor, as it allowed to more easily keep curved strips nice and straight. However, when it comes to thin edges of a mesh that are at 90 degree angles, the UV strips are incredibly tiny/thin. They're scaled so they fit within the UV grid, but their width can be soooo thin, which doesn't translate to a clean bake. Some of these edges, especially for hard-surface stuff, can't be bevelled either and therefore need to have separate UV islands.

I figured I'd try experimenting and just scale them outwards, so they're thicker. This does result in distortion obviously, but I figure it doesn't matter too much with Substance Painter...? Or am I wrong? Either way, after baking, I can't say I've seen any improvement. :-\

I was just wondering what everyone else does in these situations? I mean, for a straight strip that runs across with no turns/corners, it seems a bit pointless to cut it up into smaller pieces, right...? Or should I widen them out more in order to fill up more of the UV space so it becomes like this...?

I mean, I guess it's come out cleaner... Apart from the texel density/quality of the body... Though this is all just a test separate from my main file.

Thanks

Benjammin

There's no reason to split that way. You say you can't bevel, but you could easily add support loops to sharpen up the geo shading in that area. A hard edge is actually the same vertex count as a single bevel at render time.

Without more context on what this is for, here's how I would do it:


Remove the loops I've scratched out in red (optional, you probably don't need them in the low poly mesh), add edges on the green dotted lines. Make the highlighted edge the seam. Soften everything (optional on the seam).
Scaling the island probably won't help that much since the issue is ray projection causing the wavy line in the bake. See this thread for the technical details

DustyShinigami

Hey thanks for suggestion. And the thread about baking. I'll be sure to go through that.

When you say 'make the highlighted edge the seam', do you mean that centre dark green line? If so, I take it's essentially a case of cutting the strip in half...? And re-enforcing the hard edges with support loops?

DustyShinigami

Benjammin said:

There's no reason to split that way. You say you can't bevel, but you could easily add support loops to sharpen up the geo shading in that area. A hard edge is actually the same vertex count as a single bevel at render time.

Without more context on what this is for, here's how I would do it:


Remove the loops I've scratched out in red (optional, you probably don't need them in the low poly mesh), add edges on the green dotted lines. Make the highlighted edge the seam. Soften everything (optional on the seam).
Scaling the island probably won't help that much since the issue is ray projection causing the wavy line in the bake. See this thread for the technical details

Oh. I should perhaps clarify that the original high poly was made using Fusion 360 and that particular strip is shaped like the underside of a tube/cylinder that’s been booleaned into the surface. So those extra edges were added to the low poly to capture its curvature. So deleting those two edges will affect its shape/silhouette.

Benjammin

What I'm saying is its not good practice to split that strip into its own separate island. If you were texturing this with trim sheets and tiling textures then sure, but when you're baking onto round things you need to be careful about where seams go. 
What is this thing? How big is it on screen?

DustyShinigami

Well, in the grand scheme of things, I guess it's a minor thing. It's the bottom end of a mech's body:

I think Substance Painter has highlighted similar things with a pink line with its new and improved baker...? I just figured that element would need separating...? So because it's rounder, it should stay as part of a bigger UV island? But if it wasn't, and it had more of a 90 angle, then it should be tackled similarly to how you demonstrated - with supporting edge loops on the outside?

Benjammin

DustyShinigami said:

...So because it's rounder, it should stay as part of a bigger UV island? But if it wasn't, and it had more of a 90 angle, then it should be tackled similarly to how you demonstrated - with supporting edge loops on the outside?

I haven't upgraded substance in a while, so I'm not sure what pink lines you're referring to. 
If I were building this, I'd try to keep the seams between the 'plates' of the mech body.  I typically put hard edges in where required for Maya's smooth shading to look ok (this is a pretty good indicator of how much work your normal map will have to do), so the process would be a combination of those considerations. I would probably bevel the convex panel edges because I wouldn't want seams there.
Just practice and experiment - you'll learn so much more that way than listening to me telling you how to do it.

DustyShinigami

This is what the baker looks like now: