knees and elbow "crook, pit":)

Bunnysuit

hey,

i am working on this bunny at the moment and i have a question about modelling the arms and legs that you might be able to answer.
my problem is that the mesh at the knees and elbows interleaves at a certain angle.
you can't see that problem in these quick renderings, but when im exporting the model to a game engine there are these ugly interleaving? side effects. i tried many setups and different ways to weight the bones, but it just doesn't work how i want it to.
the main thing that i want to avoid is that the cubes (arms and legs:)) are squezzed in any possible way. so.. i don't want a realistic bend.. it would be perfect if all these beautiful cubes could just stay cubes:) maybe there is a trick to avoid these overlapping polys (maybe cut the polys in the kneepit?) that you could share!

all the best from berlin

bjoern

Mark Dygert

What app, what engine?
Pics would help, if you can, especially of the bones and the mesh deforming oddly if that is the issue.

Possible solutions:
- Could be a triangulation issue? If you are working in quads or have polys with more then 2 tris then you should check the flow of the invisible edges. Fixes are app/engine specific.

- Welding issues. Some verts might be doubled up and it looks like there is only one but there are 2.

- Smoothing errors or hard edges. Try exporting with only 1 smoothing group or no hard edges. Remember that UV seams will more then likely become hard edges or break smoothing on export, this is pretty typical and requires careful planning of UV seams.

- Interleaving, not really sure about that term. Interpenetrating maybe? As in one object clips into the other? Could be a skin weight issue, again app/engine specific.

Bunnysuit

i am using cinema 4d r11 and the engine is unity3d..

i totally forgot to link the pictures so here are two that might explain.
the thing is that you have to imagine how it looks looks like in the engine because all of a sudden i had problems uploading my mesh this morning. (nothing that can't be solved i hope)
look at the knees in the running picture.. when u see that in the engine theres is this flickering when its bend further than the actual angle allows in the pit (when the upper and lower leg hit each other) the same with the elbows.
so.. when you think it over something like that must happen, but maybe there is a trick how u can avoid it. i know that one possible way is to change the weights so that the upper and lower leg somehow get squeezed and that there is more room. but that is actually the only thing i want to avoid. i thought about making knee and elbow pads so that they could cover the flickering mesh:) i dont know.. maybe you have an idear..

by the way i hope my english isn't too bad..


bjoern

http://picasaweb.google.com/rainiemainie/BjoernsUnsinn?feat=directlink

i can't link the pictures so here is the direct link

Rick Stirling

Drop the inside loop on the elbows - you've got the green when you want the brown.



Read it all here: http://www.pig-brain.com/tut02/tut02_01.htm

Bunnysuit

thats exactly it.. :thumbup: no more try and error thank you very much!!!

kind regards

bjoern

Mark Dygert

ahh... Now I get ya.

Yep that's a great tutorial. I use a slightly higher poly version of that joint. Remember joint placement is almost as important as weighting in controlling deformation. You will always have some clipping, its a necessary evil we have to work around because the animation system most games use hasn't really changed that much in years. If you're interested in doing film or cinematic work then we can talk about a ton of other options, but real time is pretty limiting in that regard.

ablaine

That image above is so simple.. and at the same time really helpful! I'm going to have to revisit the elbows and knees on a couple of my characters.

ablaine

Is there a similar example for the shoulder joints? If I'm trying to keep the arms/torso as a single mesh I always get a terrible deformation when the character attempts to raise it's arm up to the side.

Mark Dygert

Shoulder joints operate much differently as they don't just bend in one direction but many. They can be a pain. The important thing to remember when moving arms around is that you need get the clavicle involved.

Also posing the arms at 45 degree angle helps. T pose is 90 degrees, 0 is arms resting at the side. 45 is half way between the two extremes. If you rig at 90 or 0 you're deforming from one extreme to another, it can get ugly. Rarely do arms go 45 to 90 or above 90, but when they do, use the clavicle to help the shoulder.

If we're talking about real time, its pretty character specific and shoulder topo might not need to be the same for every character, it depends heavily on their range of motion. If all they ever do is hold a gun or walk down a side walk then simple shoulders are easy, you can model and rig in that pose probably.

I normally like to have more loops running over the top of the shoulder then through the arm pit. The pits are almost always collapsing so I tend to keep kind of a low straight connection through the arm pit. something kind of like this:


If we're talking film/cinematics, then a 5 point shoulder can be put in place along with angle deformers and skin morphs. It gets a little complicated but in the end its easier to animate and gives great results.

Bunnysuit

i just want to say that i am really happy with this thread.. thank you all very much:) it helped me a lot!

and "clipping" is the word.. yes:)! not interleaving..