The JCM struggle
Masterstroke
Posts: 2,357
in The Commons
I've spent almost 9 years trying to create the pefect JCM set for my custom character still there are poses that break all the prvious efforts.
Do you believe, that a perfect set of JCMs can be done in DAZ Studio? That one set, that looks all natural and realistic for any possible pose?
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I've not really gone into JCMs, because, for me, there are so many challenges to achieving natural and realistic results in Studio ( hair, clothes, lighting, and so on ) while keeping the scene responsive, that I am only willing to expend a certain amout of time fixing things. If the available clothing, hair, lighting, shaders etc were so good that they were making the joints look bad I would pay more attention to JCMs, but I don't think we are in that territory.
I'm not a pro, but JCMs strike me as a form of counter-animating - imo it shouldn't be possible to complete a perfect set of JCMs since there are unlimited unknown combinations of poses and morphs that could counteract their affects. An important tool in the toolbox, but maximally effective in concert with other tools.
yes it might appear like an unlimited combination because you can have a bone rotated at 1.01 deg or 1.00001 deg or 1.00000001 deg etc to like 9 decimal places, but in practice, the difference in those values is nothing. therefore it is a problem with a limited set of rotations to solve. Even so, how many different rotations is probably a very large number.
the degree of freedom is different for each bone. Some bones will need correctives for when it is bent, or both bent and rotated, some bones will need correctives for when it is bent, rotated, and twisted. To complicate further, some correctives will need to be applied when two bones are rotated at the same time. For example, when the thigh bones are both outwards in the splits position, a different corrective will be needed compared with if only one thigh bone was rotated outwards. Another example is when the Thigh and the Shin are bent and rubbing against eachother, a different corrective for when the shin is rotated will be needed compared with if the Shin was not bent.
Cases where correctives will be needed for when multiple bones are rotated only applies to neighbouring or nearby bones. You dont need a corrective for when the shin is bent alongside the forearm, because they are not linked in a direct chain. But you would need a corrective for when both arms are up, or both legs, or shin+thigh, or upperarm+shoulder, or forearm+upperarm. So yes it becomes very complex to take into account multiple bones , multiple rotatation directions. But it is feasibly a limited problem with a definite solution. It's just no one in a right state of mind would ever tackle it.
And there's a reason people decided to implement muscle simulations coupled with machine learning to set up all this stuff as a more general solution, avoiding the huge amount of work in art directing these things.
this is a real problem. but the op was talking about a single character.
yes, well naturally it would be layered on top of dual quaternion skinning.
i think it is possible, but it will take a lot of effort to make the shapes and set up their drivers so they are fired at appropriate joint angles.
edit: also i want to be clear im not talking about making correctives that simply smooth out some weird artefact, im talking about using correctives to make realistic muscle/fat/flesh sim.
Quote:
"this is a real problem. but the op was talking about a single character"
Yes I did and to make things worse, you have to go through all of it with every individual character again, because there is no "one fits all" thing.
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