Keeping some points in place.

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Sir Kaput
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Keeping some points in place.

Post by Sir Kaput » Mon Jan 30, 2017 9:35 pm

I assume we're all familiar with these dancing air tube things.
First step in creating one such: dancing rectangle
Image

How do I keep the bottom two points immobile, though, such that the bottom line always remains horizontal?
I do want to be able to place it on some other object, mind (e.g. on a different, moving rectangle, "car").

The setup is fairly simple: always two points of my vector rectangle (a bit hard to see the points in the screenshot, granted), are bound to a bone using the B and I tools.
Image

I can try to fiddle with bone strength, but the result is somewhat unsatisfactory because boosting the bottommost bone strength will result in a much more rigid lower half than I would have liked, the "spine" moves all over the place instead of remaining centered and it still doesn't keep the bottom straight.
Image

How do I best achieve what I'm trying to do?
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SuperSGL
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Re: Keeping some points in place.

Post by SuperSGL » Mon Jan 30, 2017 10:24 pm

How about Bind points, should do the trick maybe add more points near the bottom and don't make them part of the bind points set up.
"Animation is not the art of drawings that move but the art of movements that are drawn."
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Greenlaw
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Re: Keeping some points in place.

Post by Greenlaw » Mon Jan 30, 2017 10:44 pm

Add another bone at the bottom that's not animating and then bind the bottom points to it. This will lock those points.

Actually, you can do this with Flexi-binding too. As in the above, just don't animate the base bone (you can use your existing bones for this, no need to add another bone.) You might want to adjust the strength of the lower bones to get an appropriate falloff in the animation.
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Greenlaw
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Re: Keeping some points in place.

Post by Greenlaw » Mon Jan 30, 2017 10:46 pm

Additional tip: if you're animating it with IK, you can disable the IK from the bottom bone. Just select Ignore By Inverse Kinematics for that bone. Alternatively, you can use Independent Angle on that bone.
D.R. Greenlaw
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Sir Kaput
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Re: Keeping some points in place.

Post by Sir Kaput » Tue Jan 31, 2017 6:33 pm

... these answers kind of confused me because I thought I already was "not animating the bottom bone".
Plus I found it super strange how unnoticeable the point binding was in that screenshot.

Well, guess what ... I forgot to actually bind the points when I was "updating" the bindings. :oops:
Sorry, just forgot to press the darn enter button. :roll:
(I don't suppose there's "bind-on-select" option for the I tool hidden somewhere?)

Anyway, thanks for then answers. I do appreciate them.
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Greenlaw
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Re: Keeping some points in place.

Post by Greenlaw » Tue Jan 31, 2017 6:43 pm

Sorry, yes, I do see in your second example that the bone is 'locked'. You can explicitly bind the bottom points to it using the Bind Points tool. That's probably the easiest approach.

A few more tips:

Flexi-binding should work too but you'll probably want to increase the strength and/or reduce the strength of higher bones to keep them from influencing the bottom points. You might even may the bottom bone taller to increase it's area of influence. Adding points about the bottom points and changing the spread a little may help too. (Note: this approach won't matter if you use Bind Points but it can give you a nicer falloff effect. TBH, though, it might not matter here.)
D.R. Greenlaw
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2019 Edtion
Lead Digital Animator, Dreamworks Animation

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