Character-Retopo, merge and/or combine meshes

goekbenjamin

Hey Folks!

I am quite unsure about this:

What i have is a shirt and a jacket.
I would now retopo both, and cut that part of the shirt away which will not be visible to preventig poking through while animation and reduces tris count.



Now the question is:
do i have to only combine the jacket with that shirt,
or do i have to combine them AND merge the vertices of edges of shirt to the jacket

Or is it event not necessary to combine them at all?

Which way is the best to dont upset riggers?

goekbenjamin

Does it even have any influence if those meshes are not merged on weightpainting?

Alex_J

would the jacket flap open in the wind? will character remove the jacket? will they do a roundhouse kick and the jacket lifts and twirls, exposing the shirt underneath? will you make a super realistic, up close render at an angle in which we will see inside there with plenty of light?

if not something like that, I'd probably just stitch them together, and split your UV's there at the intersection. Two meshes like this on top of each other are okay if the topology is closely matched. Like two dancers in unison kind of. They are in the same spot, under the same influence, so they can move around without tripping over each other. If the topology is very different, you have to tweak the vertex weights forever and go through all of your fucking animations individually to make sure it's gonna work.

disclaimer -- i'm very rookie with rigging, this is jus tbased on my small experience

Mark Dygert

It's nice if they're merged and welded together. It can be a really big pain in the ass if they just share edges. You have to make sure that the verts on each edge of the gap match up perfectly. You can't have a shirt vert hanging out between two jacket verts.

Even when they share perfectly, skin weighting is a major pain, give it a spin, you'll kick yourself in the nuts, because not only do the verts need to match perfectly but those weights have to match exactly otherwise they'll tear apart. It usually makes blending across that gap impossible so you have click on a vert, copy the weights, click on the other vert and paste. Vert by mother-f*ckin vert... It's terrible. If I was going to skin it up I'd either toss it back at you to weld or I would weld it all myself and rebake your textures for you, cursing your existence the entire time. It's something everyone should do once in their career just to learn how terrible it can be.

If you do that you need to make sure that there is a vert on the jacket for every vert on the shirt, no extra, no less and they need to match up or it will tear apart. If you have to go that far, you might as well weld it together and save yourself some verts and UV seams which both contribute to your overall vert count. Welding it, lowers those counts and makes it easier to skin and since you basically did all of the work to make them match up you might as well weld them.

Now there are some technical cases where you really want them to be separate objects, either so you can swap out one of the meshes or because there some other technical constrain the engine is putting on the art, usually a shading thing or some programmer can't figure out a good way to do something so we get shafted with a crappy workflow.

In those cases it's best to create a contiguous mesh to handle all of your skinning and then copy the weights off of it. Which is really helpful if you have a lot of different meshes that are going to go on this one character, like a bunch of different jackets, pants or armor.

Trial and error will be the best teachers. Just know that most people that have been down that path have chosen to weld it all together.

goekbenjamin

thanks guys
@Mark Dygert i understand now that merging/welding makes sense. But when lower part of the jacket is dynamic driven (unreal clothing), should i still merge them together?

Also i think it makes more sense to handle the uvs when all mesh-cutting-welding is done right?

Alex_J

about UV's, yeah you should wait until you've got the mesh figured out, but it's always good to think ahead.

Mark Dygert

So with the way dynamic cloth works in Unreal, you paint a mask for the parts that are to be simulated so it doesn't need to be a separate object or element. You just paint in the part that should simulate in the cloth tool.

If you break it into separate objects that creates another draw call. Which you might want if you're going to have the shirt and jacket completely separate and be able to toggle each on or off. If you leave them as separate elements within an object you create seams that add to the total vert/UV vert count for little to no gain, just a messy pipeline and slightly worse performance, which might be so small it doesn't warrant worry about but it still is technically inefficient and if done on a bigger scale with more things it could make an impact.

You really want to limit the number of objects and how complex their materials are because it can add up to a lot of draw calls.

If you want the coat to be really dynamic and swoosh all over you need to think about where you stitch them together and what might be exposed, like BIGTIME talked about. The cut might not be right on the side where they hang in the image above, but higher up closer to the arm pits on the back, it really depends on what you want the jacket to do.

Cloth dynamics can be pretty tricky and unpredictable especially around joints that can pinch the cloth and cause collision issues, like the arm pits and between the legs. There are a bunch of ways to deal with various scenarios but they usually require that the content be authored in a specific way for it to work. You really need to nail down the scope of your project and figure out what is required before you get too much further. If you aren't sure, you'll probably end up remaking and reworking it several times until you figure out that scope.

goekbenjamin

Great, thanks alot for that eye opener mark!
I will know try to cut it as you said near the armpit.
But that will lead to another questions about normals in general.

When i merge the cutted edge of the shirt-mesh with some vertices of the coat, isnt that a "bad mesh" because the normals are not "even"? (i hope my question is understandable )