View Full Version : Rotation values - forearm

12 December 2003, 01:08 AM
I have experimented with various setups for the forearm, but one thing that remains a mystery is why some joints, locators or curve objects return absolute rotation values whilst others will get to a specific value and then switch to the negative and return to zero.

eg, rotate from 0-90, then rotate a bit further and the value changes to -269 and then continues onwards to zero.

This plays havoc with the forearm expressions, the forearm y rot (half of the wrist rotation) jumps from 45 to -134.5



12 December 2003, 01:35 AM
are you using orient constraints? they will do that... I think its 'cos they suck ;)

try using something else, like a multiplyDivide node to get a percentage of the twist.

12 December 2003, 02:29 AM
I replaced the orient constraint on the wrist joint - the Yrot of which is driving the forearm Yrot - with a connection.
It didn't make any difference.

The wrist is/was constrained to a control object - I can use the Yrot of the control object and it returns a correct value to the forearm. The control object is free and unconstrained to anything.

However, if I want to switch to fk, the wrist control object becomes inactive - therefore I wanted to derive the forearm Yrot value from the wrist itself (or even a dummy object constrained to the wrist), which leads me back to the initial problem.

I also just replaced the expression with a connection via a multiply/divide and got the same bad result.

btw - Is there an easy way to drop a multi/div node in between your connections? I had to open the hypershade and create it then go back to hypergraph and connect it????


12 December 2003, 04:37 PM
take good care of your rotation orders... values may flip if your objects reaches gimbal lock!
to create a mDiv node in the hypergraph, you donīt have to open the hypershade to do it. in the panelMenu, just choose create->create renderNode. you get access to all utilities there. useful to map it to a hotkey...

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