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boom_saint
11-13-2003, 02:39 PM
i have created a ferris wheel, but when i rotate the wheel, all the cars tip upside down. is there an easy way to keep them pointing up while the wheel still rotates?

pdrake
11-13-2003, 04:19 PM
i don't know how to express this properly. expression. not easy to use, but that's the ticket. you might want to look into relativity. it makes the expressions a bit easier. i think dr. gear could be used for this application.

http://www.premdesign.com/relativ.html

i've used it quite a bit.

NigelH
11-13-2003, 06:59 PM
It's fairly simple provided that all of your cars are in separate layers and have their rotation points properly positioned in modeler. Then just apply follower to each car and have them rotate in the opposite direction of the wheel. So basically the follower for each car should be set to 'Pitch Angle from (P x -1.0) + 0.0'. Item to follow is the wheel, of course.

toby
11-13-2003, 09:13 PM
or just target the chairs to a null, some distance away -

Triple G
11-13-2003, 10:39 PM
Targeting works with the Z-axis, so make sure you model your chairs on separate layers, so their bottoms are pointing down the Z-axis. Go into Layout, add a null under each of the chairs, and parent each of these nulls to the ferris wheel itself, so that when it turns, the nulls go with it. Target the chairs to their corresponding nulls, and you should be good.

*edit* Never mind, that won't work....it's late...my mind's not functioning properly....just go with follower or target them all to a single null that's some distance down on the Y axis.

Darth Mole
11-14-2003, 12:57 PM
Just make the Ferris wheel with really good harnesses so the people don't fall out...


what?

Triple G
11-14-2003, 03:01 PM
Ok...the best way to do it, IMO, is to use IK. Targeting will cause the seats to flip direction when they cross 0 on the X or Z axis (depending on which way your wheel is aligned)...and using follower takes too much control out of your hands, if you want to have the seats sway for whatever reason.

Set up your wheel, model your chair laying on its back facing down the Z axis. Set the pivot point of the chair accordingly. Then in Layout, add a null and make it a child of the chair object. Move it to the bottom of the seat and set a key. Add another null (call it something like chair_goal), and move it down a good distance on the Y axis, say like 50m or so. Now, in motion options, set the wheel object to be Unaffected by IK of Descendants. For the chair, set one of the rotation channels to IK (most likely the Pitch), and leave the other channels set to Keyframes. For the chair null, set the Goal Object to be the chair_goal, and turn on Full-Time IK. Repeat this for each chair.

Now, when the wheel rotates, the chairs will stay aligned properly, and you can move the chair_goal to make them sway. You could even go so far as to set up a different goal for each chair so that you can have individual control over each, if you're so inclined. :)