Loop Topology Questions

PolyCore33

This is something I've searched many times over the course of a year, but could not find an answer to, let alone a mention of in this use case.

When you have one of these, it creates an intersecting loop. 


In Maya, it creates an error where if you insert a loop, it does not proceed to complete the other half on one side of the intersecting points, however ZBrush does not have an issue with this. In Maya, previewing a loop insert with this by holding [Ctrl], it's not previewable, or is glitched.


You would need two of these on one loop to avoid an intersecting loop, however it is not always ideal if you want to get the right curves, and for polycount density control.


Here is an example of the complex BS I did with the transition from hand to arm in order to get anatomically correct metacarpals and triceps brachii tendon in a closed loop while both being and looking clean. 

So now for my questions.

Are intersecting loops fine outside of topology editing, so long as you have even loops with no spirals?

Is a mesh with intersecting loops considered clean topology?

Will intersecting loops create complications outside of topology editing, or in other software?


I would also like to point out that Daz Studio models have plenty of intersecting loops.

oglu

For arms i would go with straight loops. No poles at all.

PolyCore33

oglu said:

For arms i would go with straight loops. No poles at all.

Why? it's not what I asked, and I can only see the down side to that. It would be nothing special, it wouldn't curve around muscles which can make some areas look blocky unless it's overly dense, and should be fine so long as joints aren't effected. it's just a terrible approach for different levels of muscle deformation unless your just making a smooth only model. However, the arms are already done. If say intersecting loops are allowed, I would only change a few areas on the underside of the arm. 

The only issue I have is that I can't bypass the front thigh muscles without using intersecting loops, or it will be overly dense. Everything else can be considered done.

FourtyNights

For a specific anatomical topology for a better silhouette, it's best to use it only on finger/toe nails, laterial/medial malleolus (ankle bones), knees, elbows + styloid process of ulna (bulging wrist bone), shoulders, clavicles (collarbones), scapulas (shoulder blades), chest + nipples (breasts + nipples if a female), a navel, and maybe a ribcage too. Rest of things can be simply cylindrical. That's more than enough specific topology already, lol.

Facial topology is its own specific thing, so I'm not talking about that, but for example, even following sternocleidomastoid muscles on the neck topologically anatomy-wise isn't necessary, when the whole neck can be just a cylindrical.

"...unles it's overly dense..." Spend more polygons on cylindrical parts such as legs, torso and arms, they'll get rounder enough, instead of complex topology with less polygons. PCs eat polygons for a breakfast, but when it comes to optimization, it's mostly happening with the complexity of textures (and their resolution) and shader in these days. I'm not saying that you shouldn't care about polygon count, but you're not as restricted with them, like we were, let's say like 10 years ago. Just don't waste them if they're not doing anything to the silhouette.

The main reason here is, that normal map is going to handle all the anatomical details. It's A LOT easier to skin/weight paint cylindrical topology to a rig, as well. If you wish to get dynamic shapes for muscles, that can be sculpted in ZBrush for additional normal map baking (+ other maps) with a wrinkle map setup, NOT worrying about the actual topology.

Mark Dygert

Are intersecting loops fine outside of topology editing, so long as you have even loops with no spirals?

In very specific cases where it is the only option that makes sense sure, that's fine. If you use it all over the place its going to drive you and other people who work with the model, bonkers. Modelers without a lot of skinning or material experience tend to focus on wonky things that cause issues for other people later on down the pipeline, don't be that guy. If you don't know, ask them.

If you are the entire pipeline, it's best to understand the rules first before you start breaking them.

Usually they are created through many hours of trial and error. More than likely people have already tried what you think is revolutionary and they decided not to use it. Just because it's new to you, it doesn't mean it hasn't been tried.

You could be creating a lot of issues for yourself if you start blazing your own trail too early on in your learning. The chances of you getting yourself lost and there being no one that can bail you out, is pretty high. Once you're familiar with the rules it's fine to question, bend and break them because you know it won't blow up in your face.

Is a mesh with intersecting loops considered clean topology?

Nope, but depending on where it is, it might not be an issue. Or it could be a pretty big deal that leads to a lot of frustration, use it wisely and do not be selfish, think of others and make sure you aren't making more work for them which could slow the project down. The more times someone has to stop and fine tune a trouble spot around a pole, the more times they will curse your very existence.

Will intersecting loops create complications outside of topology editing, or in other software?

Deformation and skin weighting tools often rely on clean loops, and assume a clean winding order. Often I'll copy the weight from one vert, quickly select the loop and paste, if that loop goes to a weird place or terminates at an odd pole leaving verts un-selected, just know I start to dislike you. That builds the more I have to interact with that kind of crap.

Tossing in poles and nutty topology could make a lot of issues. You need to be careful with that kind of topology because the winding order of the triangles will drastically affect how it deforms and shades. You might need to enforce a different winding order which also breaks loops and rings.

Again, if the person rigging and skinning has to stop what they're doing and flip some non-visible edges, that is extra work they wouldn't normally have to do.

When layoffs start to get kicked around a studio, you don't want to be the weird guy that doesn't stick to conventions and causes issues for other departments because he is dogmatic about his specific modeling approach. Those guys get cut loose pretty fast. It's good to question things and make sure you are working in the best ways possible, just don't be the guy that is inflexible and causes issue, you'll have trouble paying rent.

I would also like to point out that Daz Studio models have plenty of intersecting loops.

That's a poor guide to go by. Those models are created so the model smooths correctly on its own without the aid of materials. Most game and film quality models, will have decent normal maps that provide all of that detail, while you do want to support muscles and make sure deformation is working properly, you can let those systems do what they where designed to do.

It's best to experiment and figure things out. Use all of the poles you want, IF you're the one doing the skinning.

Personally if I was given a model with that topology, out of the blue, I'd probably kick it back and ask for something that is actually easier to work with, that is unless they had a REALLY good reason for using it, but then we probably talked about it ahead of time, I signed off on it and I knew it was coming. But then again I usually work with people that are really good about communication and they don't sandbag me with weird shit. out of the blue.

oglu

Even in games you have skinsliding and PoseDeformers these days and they work best with an even quad topo. 

PolyCore33

Sorry for the very late reply, and thanks for the responses!

This is pretty much what I've got concerning self-intersecting loops and re-did almost everything from the knees down. So that's five self-intersecting loops from the waist down, although I don't really think there will be any issues now. All poles were necessary and think it has good balance between good shape curve to avoid blocky-ness for muscle deformation and a character muscle morph, polygon density control, and good animation, but I think the back of the knees may still need some tweaking.

I plan to rig the final product myself and sell / license it with an 18+ variant, so please post your concerns and or suggestions.



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