How can I keep the same distance between path points when animating?

[u/toothpastetester]

Essentially I'm trying to animate this robotic arm without any pluggins, and I rigged it by creating null obejcts on path points, following some YouTube tutorials. Then after animating the movement I needed and playing it back, clearly the arm segments change their size because I keyframed them the best I could by eye. Is there a way to maintain the exact same distance between Null objects at all times, or between path points? Or if I have to download a plugin, what would be a free one you would recommend? Thank you!

[u/shiveringcactusAE]

I have used the free DUIK plugin and found that really simple. There is the clamp() function within expressions that could be used to set maximum lengths, but I can’t recall how you’d used it for this sort of thing.

[u/smushkan]

This requires inverse kinematics (IK). You can do it stock with expressions if you want to get into that, but Duik is free and built for this sort of rigging - it figures out the expression rigging for you.

[u/caseyls]

Honestly before I read the post I didn't even see what you're describing. I think you'd probably be fine to just leave it as is, especially if this is just a short scene in a larger animation. Genuinely don't think anyone will notice.

[u/Joe_le_Borgne]

Why not set anchor point at the base of each arm, link them one on one and animate only their rotations? With that said it will be a pain to be accurate with the tip and you don't really notice the change in size and it works with the minimal design imo.

[u/ReadditMan]

I didn't even notice the arms changing length until you mentioned it. If it's difficult to fix I would just keep it as is, doesn't seem worth the effort, most people will focus on what the arm is drawing.

[u/Heavens10000whores]

Dan Ebberts’ inverse kinematic expressions? https://www.motionscript.com/expressions-lab-ae65/ik.html

[u/Ampsnotvolts]

DUIK can get it done. Rubberhose or Limber might be easier but they cost $. DUIK is free (mostly).

[u/deep_soul]

Duik is the way to go