Arc-Solver Madness?

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DrNibbert
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Arc-Solver Madness?

Post by DrNibbert »

Hey everyone!

i want my Bone-Chain to bend in an evenly, round way (for a character with noodly arms like finn from adventure time) and i figured that the Arc-Solver could be the right tool for that?

But when i activate the arc-solver-option everything is going bananas and the Bone-Chain is flipping like crazy back and forth.
Check it out:
https://www.dropbox.com/s/p9wyndb37hbf4 ... 0.mp4?dl=0

Can anyone tell me how to use the Arc-Solver propperly, what it's intended purpose is - and what would be the best way to create evenly bending Bone-Chains (in a IK-Spline-Way)

Thanks a lot!!
Showreel 2018 https://vimeo.com/254290989 - Moho 12.5.1, macOS 10.10, Adobe CS6
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

For 'noodle arms', I just use Sketch Bones. Then I can make the arms wiggle and curve any way I want them too...just animate them like a tail. Since I don't want that all the time for a character, I add a rig switch (using Victor's rig swapping trick) to replace the arms with regular joint arms when I want that.

If you don't want that much flexibility in the arms, another 'noodle' setup is to use three bones, an elbow constraint, and minimal points in the arms. Victor has a good demo of the technique here:

viewtopic.php?f=9&t=20410&hilit=noodle

If you're using only vector art, it's a super easy technique, and you can make it swappable just like with the Sketch Bones variation.

On one of our shows, I found the technique didn't work as simply with image layers because you need a lot more points to smoothly bend an image layer, but I was able to adapt it using a custom mesh. It was a little tricky to set up but worked out nicely in the end. I think I describe in the thread but didn't show any pictures because the show isn't out yet. If I have time, I'll try to make a demo with one of my own characters.

Hope this info helps.
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

About the Arc IK Solver option: this uses a different IK solution that basically 'stiffens' the IK between the joints so the 'limb' doesn't bend sharply. But you need three or more bones in the chain for this to work, otherwise, it can go wacky as you discovered.

The option works but I rarely use it in a character because I generally require a lot more flexibility when animating arms and legs. I recommend going with any of the techniques described in my first post.
DrNibbert
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Re: Arc-Solver Madness?

Post by DrNibbert »

Thanks for your detailed response! I'll give the sketch-bones a try... I allways felt like too less control and i have to keep a steady hand while drawing, otherwise i'll get sharp corners :?

But Arc-IK is still a mystery to me... have you watched my example-video? I used more then 3 Bones and had Arc-IK switched on for every bone in the chain, but still i got this jumpy/flipping result.... any ideas what causes this? Did i set everything up correctly?

Thanks a lo!
Showreel 2018 https://vimeo.com/254290989 - Moho 12.5.1, macOS 10.10, Adobe CS6
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synthsin75
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Re: Arc-Solver Madness?

Post by synthsin75 »

IMO, the arc solver works best with a target bone.

Victor demonstrated the difference here: viewtopic.php?p=150099#p150099

What it attempts to do is create a smooth arc of the bones to reach the target, as opposed to each bone trying to figure out what to do on its own, without the arc solver. Without a target bone, Moho will use any rotation to reach the position of the last bone in the chain, including 360 degree rotations. The target bone prevents that, but you may still need to add a rotation key (usually with step interpolation) to the first bone in the chain to change the direction of the arc.

For example, say you want to make it arc upwards as you bring the target closer to the base of the chain, but it wants to arc downwards. At the start of the move, you'd set a step rotation key on the base bone in the direction you want it to arc...and again when you what to change the arc direction.

Here's an example file: http://www.filedropper.com/arcik
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

DrNibbert wrote:Thanks for your detailed response! I'll give the sketch-bones a try... I allways felt like too less control and i have to keep a steady hand while drawing, otherwise i'll get sharp corners :?
Sketch Bones actually works quite well. I use it all the time for tails, but also used it for noodle arms, eyebrows, hair, rope and chains.

I don't think I've ever had a problem with 'sharp corners' when using Sketch Bones. If you're hand is unsteady, just draw the path slowly...the tool draws a preview of the path so you can see what it will do before you release the mouse button. If it's not exactly what you want, just draw it again until it looks right.

Tip: Always 'sketch' from the base to the tip of the entire bone chain. This way, you'll be sure to set a keyframe all the bones in that chain. If you only key part of the chain, the chain may not interpolate from keyframe to keyframe the way you expected.

Hope this helps.
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

Oh, another way to make noodle arms is to use the Follow Path tool. This way you can use a spline to deform the artwork.

TBH, this is not an ideal technique for arms though. Follow Path's deformation quality is pretty nice but you can't parent items to the end of the path like you can in a bone chain. But if that's not important, it can still be a very useful technique.

I hope someday we get an actual spline deformer that we can parent items like bones and groups to, as an alternative to bone chains.
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synthsin75
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Re: Arc-Solver Madness?

Post by synthsin75 »

Greenlaw wrote:Oh, another way to make noodle arms is to use the Follow Path tool. This way you can use a spline to deform the artwork.

TBH, this is not an ideal technique for arms though. Follow Path's deformation quality is pretty nice but you can't parent items to the end of the path like you can in a bone chain. But if that's not important, it can still be a very useful technique.

I hope someday we get an actual spline deformer that we can parent items like bones and groups to, as an alternative to bone chains.
You can have any layer or group also follow that same curve, just set to the end you want it parented to. You could even use follow path to distribute any number of layers along the same curve.
DrNibbert
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Re: Arc-Solver Madness?

Post by DrNibbert »

Greenlaw wrote:Follow Path tool. This way you can use a spline to deform the artwork.
:shock: Wow, i didnt know about this one yet.... It's alt+Follow-Path-Tool right? That really seems like the closest to the spline-IK-feature i was looking for! :-)
If i could orient a bone-chain along a spline, that would be perfect :-)
Showreel 2018 https://vimeo.com/254290989 - Moho 12.5.1, macOS 10.10, Adobe CS6
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

DrNibbert wrote::shock: Wow, i didnt know about this one yet.... It's alt+Follow-Path-Tool right? That really seems like the closest to the spline-IK-feature i was looking for! :-)
If i could orient a bone-chain along a spline, that would be perfect :-)
Yes. Normally, it's used to attach an item to follow the curve, and Alt-Click attaches the item and uses the shape of the curve to deform it. To use it for 'limb' animation, just animate the curve.

BTW, what Wes wrote is correct! Since you can attach more than one item to the curve, in a sense, you can 'parent' things to it. I just did a test where I attached an 'arm' to a curve with Alt-Click, and then a mechanical 'claw' to the starting pont of the curve. When I move the points in the curve, the non-deforming claw does sort of 'follow' the end of the arm. Of course, it's not really following the 'arm', but it definitely has the appearance of it. I'd still need to keyframe the orientation of the 'claw' but that's no big deal.

This is not exactly what I was thinking, like parenting a hand directly the wrist, but it's definitely workable...just a little extra work to animate.

That said, for something like this, I still think using Sketch Bones will still be easier to animate and offer more control.
dondo
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Re: Arc-Solver Madness?

Post by dondo »

This is slightly off-topic, but... Greenlaw, you mentioned above something about "Victor's rig swapping trick." Could you point us to something that describes what that means?
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

Sure. Here's Victor's video demonstration of the technique:

https://www.youtube.com/watch?v=iGCCDkDNzcI

And the original thread:

www.lostmarble.com/forum/viewtopic.php?f=9&t=30445

It's a great technique. I like to use it when I need a completely different limb setup for different angle views.
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

This is where I wish the devs would add the ability to keyframe the visibility of individual bones and bone groups. That could simplify a setup like this. There's a script solution for that but it's one of those things that really should be a native feature.
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synthsin75
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Re: Arc-Solver Madness?

Post by synthsin75 »

Greenlaw wrote:This is where I wish the devs would add the ability to keyframe the visibility of individual bones and bone groups. That could simplify a setup like this. There's a script solution for that but it's one of those things that really should be a native feature.
When I find the time among other scripts I'm working on, I've been debating whether animated bone visibility should be a priority.
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Greenlaw
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Re: Arc-Solver Madness?

Post by Greenlaw »

Here's an example I just happen to be playing with at the moment:

Image

The legTurnL and legTurnR SBDs are used to 'smoothly' rotate the digitigrade leg 720 degrees. During the turn, the bones are swapped out to make it easier to animate the knee when pointed in the opposite direction. Like this:

Image

Turning the SBD the other way reverses the turn.

A better example might be the T-Rex I rigged for our Boss Baby show on Netflix. I'll think about recreating that setup for a demo.
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