How to control start and end point of a comet

NeOreo

I am once again asking for your assistance.

I have animated a comet that scales up and down for which I used 2 bones:

The green bone, which is parented to the red one, starts scaling up the comet and then the red bone scales it down. The issue I'm having is, that the developer needs to be able to control the start and the end point of the comet and ideally that would also affect the length of the comet. Obviously my setup doesn't work in this case since if you move the anchor of the parent bone, the child moves with it.

Also at the head of the comet is a star with it's own bone that needs to be linked to the movement of the comet. And behind everything is a trail of particles, which I made by attaching small bones with with particles to a larger control bone. But I've been only focusing on the comet controls so far, because trying to figure out how to also link the star and particles would make my head explode.

I've tried creating a path constrain with which I was able to control the tail and head separately, but the I couldn't control the scaling down and the bezier curves make the straight movement more complex.

I've also tried playing with IK constraints, but I can't really tell you what I've been doing, because I still find them a bit confusing.

So is the there an easy way to create "nulls" with which I can control the tail and the head location of the comet.

Misaki

NeOreo It appears to be a somewhat complex condition, so I apologize if I misunderstood the condition, but I guess that what you are looking for is a transform constraint. Instead of making the red and green bones parent and child, I think it would be better to use transform constrains to affect each other's position. I just thought that there might be times when you want to move the position of both bones together, in which case you should have a position control bone to move the two bones.
Or maybe you could turn off the scale inheritance of the green and red bone and control the distance between these bones by the scale of the parent bone.
I have attached a Spine project for reference as it is difficult to explain in text:

control-of-two-bones.spine

2kB

NeOreo

Yeah sorry, I might have complicated thing in writing a bit. I appreciate the spine project, but after fiddling around with it, I wasn't able to get the result I wanted. Could be just my lack of understanding of how the rig you provided should work haha

I recreated a simple example in after effects.

I'd like to have the bones set up in a way, that when I move one bone, they are still pointing towards each other. If that makes sense.

Misaki

NeOreo Hmm, if you just want the same behavior as the example, you can achieve it with the following setup:

Here is the Spine project file:

bone-control-with-ik.spine

560B

NeOreo

This is getting closer, but what I also need is the double bone setup from before. Here is how the animation looks now. The goal is to make the rig in a way, that the developer can simply move the coordinates of point A (tail) and B (head) to make it land on different locations.

The green bone scales up the comet, and the red one scales it down. That's why I made the red bone the parent of the green one. But then moving the green bone, leaves the red bone in the same place, and moving the red bone moves everything.

I'm sorry for complicating so much, but I really appreciate you taking the time to help.

NeOreo

Aaaaah ok never mind, I figured out how to set up the IK setup that you've sent me.

Thank you sooooo much again for all the help!

Misaki

NeOreo Glad to hear you figured it out! Thank you for getting back to us! 🙂