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[Francesco]

Hi all, I've been playing around with skeletons and animation, and I noticed that it is not possible to change bone lengths while animating a figure - well, you can, but actually it changes the whole figure, not that particular keyframe.

I think it could be handy for making mechanical stuff like pistons or for making weird models like the rubber-man.

A couple of gifs attached - yeah, lots of time underhand

[texel]

It would be also good if Anim8or could support translation of bones relative to their bases (bones could be not always attached to each other).
_ It could make the same result as you want
_ You could also make animations with objects which could be separated from each other (ex: a character which throw a ball: the ball could have its bone)

[neirao]

i think then this is possible...

we can use morph target for do it...
but if have in bones this possibility,will be cool..

[Francesco]

Yes I thought about morph targets, but it looked too much of an hack for me.

I am thinking about another thing too: "stick bone to this line (or to this point or whatever possible)".

The animation depicted in the first gif does actually work - the one named "bone rotation" - but it's a weird way to do such things.

I tried animating it in the "natural way" (the way pistons, rods and crankshaft work in engines), but I wasn't able to make a complete cycle.

I exported the figure and the sequence in the file attached to this post. Putting five keyframes as I did in the attached sequence results in messing up one good half of the animation.

The problem here is keeping the final bone always (and perfectly) aligned to a particular straight line.

Take a look to the animated gifs in this page: http://auto.howstuffworks.com/engine2.htm. These (very well done) animations are almost perfect, but they suffer from the same alignment problem (you can notice it better if you pay attention to the piston's edges and to the reflections, while the piston reaches the lower limit).

I think that the program used to make those animations lacks of that "stick to this line" feature (or maybe it was there and the author did not use it).

About messing up the animation I attached, I think that Steve has recognized the problem at a glance, and hopefully it won't need more than a minute to fix that.

I don't really know if a "stick to this line" feature would be easily feasible, but I'd love to have all three new features while rigging and animating (bone lengths keyframes, detachable bones and "sticky" bones).

Anyway I'll go on having fun Anim8ing the way I can, I believe there are always new and interesting workarounds to do the trick with the gear we already have.

[hihosilver]

Telescopic Bones

Edit:  Good catch there on the malformed link

[Francesco]

Yes hihosilver, that's another way to work around this missing feature, and that's a really well done animation - I made my sequence without even thinking at limiting the joints...

(The link is malformed, fix it, it is a really good article to read.)

By the way, is that website yours hihosilver? The article about the cybobird - and the painting in particular - is truly amazing. I wish I could draw that way!

[floyd86]

Fixed:
Telescopic Bones

[xalener]

A feature I'd like is to have bones always face other bones. If you could get two bones facing each other, you'd easily achieve a hydraulic effect.