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View Full Version : Heading doesn't tilt when Pitch, or bank are rotated



THREEL
07-23-2012, 02:52 AM
I know there is probably a simple explanation for this, but here it goes, anyway. I have modeled an object and brought it into layout. For easier rotation, because the object is irregularly shaped, I introduced a null to the scene, centered the null to the object, and then, parented the object to the null. My problem occurs when I tilt the null. The null (and object) tilts with any movement I give to the pitch, or bank, but the heading axis stays parallel to the ground. If the heading axis is already parallel to the ground, shouldn't the heading axis tilt when I make a movement on the pitch, or bank axis? I'm trying to rotate this object like the Earth spinning on its tilted axis.

Thanks!

3DGFXStudios
07-23-2012, 03:08 AM
What's your Coord System set to? I think it set to world space in your case. Try these out Local, world, parent. See the difference ;)
You can use the rotation order switch in the motion modifiers.

RebelHill
07-23-2012, 05:58 AM
Its rotation order... using different axis can sometimes give the effect you're after, though usually it makes it totally wrong. Watch the vid...

http://vimeo.com/2649637

erikals
07-23-2012, 07:01 AM
 
and... > http://vimeo.com/2824431

 

THREEL
07-23-2012, 07:24 AM
Well... I changed the Coordinate System to Local which tilted the heading axis, so its not parallel with the ground anymore, but as soon as I put it into motion, it still is rotating on an invisible vertical axis. I don't think I'm experiencing gimbal lock, and I've tried rotating the object in different orders, but nothing seems to make it right. I'm on v. 8.5.

erikals
07-23-2012, 07:37 AM
share scene maybe...

THREEL
07-23-2012, 08:07 AM
share scene maybe...

I just cleared the scene and tried it with only a null. It doesn't matter which coordinate system I choose, or which setting I rotate first, it seems like I'm getting a tumbling effect. I have the heading set from 0 deg to 360 deg. over frames with an offset repeat to continue the spinning motion. I have the bank set at 30 deg. constant from the zero frame to get the tilt.

RebelHill
07-23-2012, 09:30 AM
it doesnt matter which co-ord system u use, the rotations are ALWAYS stored, and interpolated as the parents local axis (parent mode). As pointed out in the vid, simply keying rotations whilst controlling input via the items local axis only creates drift during inbetween.

Rotation order in LW is H,P,B... its like having 3 nulls parented to each other, each only able to rotate on a single axis.

Basically, if u want to orient against a certain axis of rotation, then the way to solve it is to parent ur item to a null, and rotate that... transform the parent space... then rotting ur item within that space.

The vids on parenting and rotation in my YT link'll give u more info on all that stuff in LW too.

Actually all that said... there is one thing u can do for quick stuff like this, and that's to key in whatever axis mode u like, but add the quaternion booster motion modifier to your item, then rotations will come out as ud expect.

THREEL
07-23-2012, 12:39 PM
it doesnt matter which co-ord system u use, the rotations are ALWAYS stored, and interpolated as the parents local axis (parent mode). As pointed out in the vid, simply keying rotations whilst controlling input via the items local axis only creates drift during inbetween.

Rotation order in LW is H,P,B... its like having 3 nulls parented to each other, each only able to rotate on a single axis.

Basically, if u want to orient against a certain axis of rotation, then the way to solve it is to parent ur item to a null, and rotate that... transform the parent space... then rotting ur item within that space.

The vids on parenting and rotation in my YT link'll give u more info on all that stuff in LW too.

Actually all that said... there is one thing u can do for quick stuff like this, and that's to key in whatever axis mode u like, but add the quaternion booster motion modifier to your item, then rotations will come out as ud expect.

You know. While I was waiting on a response, I got to thinking about it, and your answer was the one I came up with, too. Spin the object, then give it the rotation with the null. I guess you learn, or in this case, relearn somethin new, or not so new everyday. :D I was just thinking maybe spinning objects on their own axes, without the aid of a null for specific tilt, is the way to tumble things like asteroids. :) The vids are quite informative. I'll have to file them in my favorites folder under 3D modeling/animating info. Thanks for the help!