Playing Guitar: Upper Arm and Forearm

Community Beginner ,
Feb 12, 2019 Feb 12, 2019

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I am trying to have a puppet play a guitar.  I have separate groups as follows:

      Left Hand

      Guitar

      Left Upper Arm (Forearm and Upper Arm Layers)

This is so the Left Arm is behind the neck of the guitar and the Left Hand are in front of the guitar.  I have Dragger Tools for the Left Arm, Guitar and Left hand.  When I move the Left Arm (with a Dragger Tool on the hand), the Elbow and Forearm distort.

Is there a way to:

1. Restrict the movement of the Left hand along the neck of the guitar - sliding up and down, but not off the guitar's neck?

2. Make the Left Elbow have less motion as the Left hand moves up and down the guitar's neck?  Sort of pivoting at the elbow.

Also, is there a way to step record - similar to claymation?  Basically, putting the puppet in different poses throughout the scene and having Character Animate fill in the gaps - similar to key framing.

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Explorer ,
Feb 13, 2019 Feb 13, 2019

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For your keyframe Idea you might record your poses and then ease then into each other. You know what I mean? In the timeline, you can ease in and out most of your recordings by hoovering over the end of those bits.

For your other problems I don't know for certain. The first one sounds like you might do with the magnets, maybe you can move the hand along the object it's stuck to. I don't really know if it's completely stuck. Haven't worked with it yet.

Second: Have you tried experimenting with Arm IK? I found movements much more realistic, when I used it. Maybe it works for you?

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LEGEND ,
Feb 13, 2019 Feb 13, 2019

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I have not worked out how to restrict movement along the neck of the guitar. Best I have had luck with is getting the angles right so the arm movement just stays close.

Magnets stick to one location... but I wonder if you can put a series of magnets along the neck and turn different ones on - the hand might then move in a straight line to the next magnet... interesting. I have generally found limited use for magnets however as objects can generally have one parent. You cannot have say one end of an arm attach to a body, and the other end attach to some other parent object. Its always a child object (like a ball) attaching to the parent) a hand. This has come up as a restrictions of magnets many times (e.g. cannot put a lead between a dog and the dog walker easily).

So my best attempt so far is to just record slowly and avoid the guitar moving too much. A short clip is right at the bottom of https://extra-ordinary.tv/2018/04/21/debugging-character-animator-eyess/  (the rest of the blog is not relevant - for some reason I through the clip up there!)

Regarding stop frame recording, CH has a “record one frame” and “record two frames” keys for this. You can even onion skin (see the previous frame semitransparently) to help. (Its in the menus somewhere.) So yes, you can do animation that way, one frame at a time. I think it is like control-1 and control-2 for 1 and 2 frame recordings.

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Community Beginner ,
Feb 13, 2019 Feb 13, 2019

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Thanks both of you for your advice.  As a work around, I have created multiple versions of the Left Upper Arm, Forearm and Hand - each in a different position on the neck of the guitar (fret 1, fret 2, etc).  I then created a separate trigger for each fret position.  Pressing each trigger key will move the arm and hand up and down the guitar neck.  The real issue was the left forearm - as the hand moves, the forearm tilts forward and changes shape, something CA has trouble computing.  By adding different guitar positions in each trigger, the guitar moves slightly to accommodate the new arm Y-axis position.

I will take a look at the record one frame tool - thanks.

I have tried Arm IK, but it did not work.  There is too much forward tilt involved.

Do you know if there is a way to keep a body part (hand) from stretching at all?

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LEGEND ,
Feb 13, 2019 Feb 13, 2019

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Stopping body parts moving 100% can be tricky. The normal approaches are

  • Make something independent. A child cannot move a parent across an independent barrier. Eg make the hand independent and attached to the forearm.
  • Try pins if there is a parent layer to pin to.
  • Add 50,000 sticks until it stops moving.

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Community Beginner ,
Feb 13, 2019 Feb 13, 2019

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I like the 50,000 sticks idea, but I don't have 40.3117 hours to draw them all (that's one stick every three seconds without stopping).

I will try pins.  Hopefully that will work.

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LEGEND ,
Feb 13, 2019 Feb 13, 2019

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I prefer sticks over pins. Pins can fix thing relative to the parent layer (so things stop moving). Sticks keep things from moving relative to each other in the current layer. So I do things like a stick across the top of the shoulders (to limit the impact of the neck on the main body, then sticks from the shoulders down the side of the body (to limit the impact of the body on the arms)

9417B5F9-5E6D-47E8-8284-B6BD80AEBD1D.jpeg

The red above is the sticks I often use. SOmetimes I also put sticks along the jaw line above the neck to stop the face shape warping near where the neck joins the body, if the head is not independent.

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