Modifying topology after bake?

jordank95

Trying to get an asset under a certain polycount and I’m having issues. The more I modify the topology, the more the shapes get further away from the high poly. Is it bad to modify the topology and get rid of some edge loops AFTER baking? Seems that’s the only way this is gonna happen. 

poopipe

Yes it is,  bake it again after your edits

ZacD

If you are change the normals of the lowpoly, you should rebake. You could technically remove edge loops that are not contributing to the shading and have no issues.

Post some pictures and show us the exact problem you are facing, and we might be able to give better suggestions on how to resolve the problem without resorting to what is typically considered bad practices. 

Mark Dygert

Most of the time you should rebake, especially if you're mesh will be deforming. There are some errors that look ok when the model is in a static pose but as soon as it twists or deforms the errors show up.

When you bake normal maps it looks at the low poly and looks at the high poly and whatever is different, is captured in the normal map. A normal map IS the difference between the low poly and high. When something changes, the difference changes also... but if you don't bother to update the normal map... /shrug 

Sometimes the change is so small that you won't notice or its in an area that no one cares about so it's fine to let it slide. BUT those cases are usually rare, most of the time you're probably better off to rebake. If you're workflow makes that a difficulty then you probably have some kinks in your pipeline that need to be straightened out. A decent pipeline will support rebaking without much fuss.

To put it another way, it's like putting custom fitted facial prosthetics on an actor.



They mold them onto to the actors face, they glue them down and blend them so the flow seamlessly into the actors skin/makeup. They usually aren't reusable. Sometimes you can reuse them, if you're light on the adhesive and not doing a lot of blending on the edges. Or some companies consider their prothetics reusable, but it requires melting the material down to reuse it.

BUT you really can't just peal off a prosthetic and stick it back on the next day, let alone try to stick it to a different actors face. If your FX budget it so tight that you're recycling facial prosethics, you probably have bigger issues.

It's a lot like normal maps, in some cases you can, but you're probably being a cheap bastard that is cutting corners. You might get away with it but if that's you're pipeline? nah... you're doing something wrong, fix your pipeline.

Neox

Yes you should rebake, so everything is in sync, otherwise you might see normal issues.
But besides AO, rebaking for a normal game asset should be seconds in tools like marmoset, so this should basically be a non issue.

Noors

Yeah, also a reason to not edit normal maps destructively. You should be able to rebake them and replace them in your workfow without hassle.

Nice Mark, never thought of such illustration

Alex_J

Mark Dygert said:.....

Fantastic. Not that I distrust anybody here, but I was left with some doubts as I have done quite a bit of editing after baking and never noticed a difference. However, this was very quick n dirty work -- not focused on high quality whatsoever. So it's not like I was looking very close.

But this explanation makes it very clear and easy to understand why exactly it's generally bad. Thanks.

musashidan

@BIGTIMEMASTER there is another baking workflow that uses a skewmesh and object to tangent space conversion. Possibly you confused the workflows?

Alex_J

I don't think so. I just didn't know any better.

Was doing a lot of new stuff all at once --  modular characters and rigging -- and of course I didn't get the topology right first time so I just started adjusting it as needed. I didn't expect nor see any problems from that, even with the characters animating in engine, so never thought nothing of it. Figured it was totally fine.

But this was on character arms and shoulders with noisy textures from a third person/top down perspective. And these were models I made very rapidly on a deadline, so the "it's good enough" stamp was always ready to strike quickly.

pior

Yup you should rebake - but mostly, you should also keep in mind that anything takes iterations to get right.

So instead of hoping to get a perfect/easy rebake automagically, I'd rather suggest to do as many hacks as needed on the low, to consider the first bake as just a temporary thing, and then be ready to readjust/rebake/resculpt/reUV most everything if needed.

Also (at least for organic/subtle stuff like character faces) I think it is way better to work on the low and high at the exact same time, rather than hoping to do one after the other. Especially for stylized characters, a resculpt can be very fast and can benefit a ton from having a solid texture to sculpt over. Grey sculpts are just a tiny fraction of the whole story.

Overall, most of the issues I see people running into come from some misguided belief about these workflows being linear - whereas they really should be thought of as non-linear.

Note that none of the above applies if one is working from a solidly established base that is set in stone by production. But if we are talking about iterations in order to get an artistic vision polished from scratch, then yeah, iterations are necessary - and if a pipeline is so stiff that it doesn't allow for them, then it's a wrong pipeline and it needs to be rethought.

You should also post what you are actually working on - as all the suggestions above are mere assumptions based on 3-liner OP.

jordank95

All makes sense. Thanks so much for clarifying everyone! I managed to get my polycount down to where I needed to while maintaining the shape I wanted that still baked well.

Thanks again