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bombay
04-18-2007, 02:12 AM
Hi every one,
I'm new in the forum and in LW world, and I have some question:

I'm Trying to animate a robotic arm, but I have some trouble with the piston path. As You can see in attached img the action center of Inner Piston and of Outer Piston don't share the same action line. I have done some test with target, goal, follower but i don't reach any result; and also in old thread I don't found nothing like that.

Can you help me.

Thanks
Alberto

toby
04-18-2007, 11:43 AM
Not sure I understand, (I'm at work so I can't open your scene) but generally when you have a piston and cylinder, you want to have them both pointing towards +Z in modeler, then target them at each other in Layout. Maybe that will help?

RudySchneider
04-18-2007, 03:28 PM
I'll bet you could benefit from Kurtis Harris's tutorial, Setting Up a Hydraulic Cylinder, which you can find here:
http://www.newtek.com/lightwave/newsletters/v2-n3/index.html

Mr. Wilde
04-19-2007, 07:03 AM
Add a null and parent the outer piston to it. Place the null now on the action line of the outer piston. Since the outer piston is its parent, the null will move with the outer piston and always stay on the action line.
You can now choose the null as target object of the inner piston. :)

Mr. Wilde
04-19-2007, 07:11 AM
Add a null and parent the outer piston to it. Place the null now on the action line of the outer piston. Since the outer piston is its parent, the null will move with the outer piston and always stay on the action line.
You can now choose the null as target object of the inner piston. :)
No, just recognized that doesn't solve it properly. :stumped:

voriax
04-19-2007, 08:11 AM
It's a toughy.. I tried to get it working earlier today and got no joy. It's the offset pivot on the outer section that's screwing it up, because using IK to make the lower point to the upper wont work properly with the offset pivot. If it was a straight piston config like is in the tutorial, there'd be no probs.

bombay
04-19-2007, 09:32 AM
Thanks for the suggestions, I think to have found a solution with a follower and a null as goal. In attached a test scene.

Alberto

voriax
04-19-2007, 09:28 PM
I tried a few more things, but the quickest and easiest for me was to use IK and offset a null on the end of the outer piston part, and offset it to match the piston rod as it moved. Clumsy if you're gonna be doing complex animation with it, but you could write an expression or use a plugin to automatically offset the null according to the movement or rotation of another part.
I've attached the scene.. just uses the same objects you included.