View Full Version : Compass project help radius arms

Nigel Baker
02-17-2013, 02:38 PM
Hello All,

I am looking for any suggestions to help out with this project.
I am working on a compass project that will be used in many different scenarios over and over so rather than just moving the arms of the compass every-time the radius is changed,
I was wondering what is the best way to do this, even using the new IK and Genoma.
All help and suggestions are very welcomed.

Here is a grab from the work in progress,


Many thanks in advance.


02-17-2013, 03:12 PM
What... you just wanna be able to rig the compass to open and close its arms??

You can use IK if you like... tut... http://www.3dworldmag.com/2012/12/20/tutorial-get-to-grips-with-lightwave-ik/

But honestly there's little need, just 2 bones operated on FK would do u fine, with the whole thing parented to a null located at the needle position.

02-17-2013, 03:26 PM
Wouldn't even need Bones, with a multi-layered object. Six o' one,....

Nigel Baker
02-17-2013, 04:18 PM
Hello All,

Thanks for the replies.
I wasn't even thinking like that but a null at one needle point working two bones.
I must look at that. I have never really used bones so I am completely new to it.
And was thinking more like the actions of a real compass which seems reversed thinking, to the null (I think?)

I know it is only two arms moving but I thought some form of IK would safe me twice the work of moving both compass arms away at the exact amount each time.
And it needs to be precise, also I thought if I did it with bones I might learn something new as well.

Any other suggestions please reply.

Thanks also for the link, I will have a look at it also.

Kind Regards,

02-17-2013, 05:01 PM
Use expressions ?

Each arm in its own layer. The pivot point would be at the top, where they attach to the center piece of the compass.
As you rotate one arm out, the other arm is set to mirror the angle?

All of this parented to a null. That null would be the point where the needle sits and rotates around.

Just spitballin'

02-17-2013, 05:18 PM
The question is: where to place the Pivot?

Depending on the animation's needs, at the point of one arm might make sense. The handle might make sense. Somewhere else might etc...

Worst case is where two different places are needed. Like the animator might want to spin it around one needle, then the handle, then the other needle. Dynamic Parenter may work there.