Rotating an object more than 90 degrees over a second

Alright… I’m sure that this question has been asked a million or so times before but even after searching numerous databases, I’ve yet to find a simple way to do it that doesn’t involve excessive use of orthographic mode, the shift key, trial and error, or the ipo window… most of them weren’t even directly answering my question anyway.

Right, so… I’ve got a mesh that has its center on one end. I want it to rotate to a certain location… so, of course, I insert a Rot key, then frame forward 25… (25 fps, ya) I rotate the object and then put in the 2nd Rot key… the starting and ending positions are just fine, but the object keeps rotating on all three axes, even when I just want it to rotate on the Y.

Is there a constraint or something that I could use to easily fix the problem?

In the IPO window you’ll see IPOs for RotX, RotY, and RotZ. You can simply delete any you don’t need.

There isn’t quite enough information to know what the problem is, but try this first. Before doing your key framing make sure you select the object and press ctrl-a and click the pop-up dialog. The ctrl-a makes the local and global axis the same and will probably solve your problem.

If the above doesn’t work post your blend file so we can look at it.

GreyBeard

Okay, sorry that I didn’t provide enough info. I failed to realize that this even only happens when working with CP relationships. Ctrl-A doesn’t help, unless I’m doing something wrong…

Here are two, small, simple example files that I made and zipped.

www.geocities.com/cronocat0/blend.zip

Note, all of the rotation keys here were placed in front view, even though the objects are spinning on more than one axis.

Right, so… I’ve got a mesh that has its center on one end. I want it to rotate to a certain location… so, of course, I insert a Rot key, then frame forward 25… (25 fps, ya) I rotate the object and then put in the 2nd Rot key… the starting and ending positions are just fine, but the object keeps rotating on all three axes, even when I just want it to rotate on the Y.

From look ing at the files I noticed that you start position was ok but the end position wasn’t just rotated on one axis (ie. the y). I believe that this was because you were in perspective mode in the 3d modelling window and you were trying to line things up orthographically.

Here’s how I would accomplish what you are trying to do.

  1. add empty at rotation center. clear the rotation of the empty (Alt-r).

  2. place your object where you want it rotated to the starting position. press ctrl-a

  3. parent the object to the empty.

  4. insert your key frames.

Hope this helps,
GreyBeard

Alright, I tried what you told me to do, and maybe it sorta helped?
I’m now able to simply delete the two axes that I don’t need without problem, but I’d still kind of like a way to not have to deal with this in the first place. After cutting parent ties, clearing rotation, and clearing ipo values, applying size and rotation, then, after switching to ortho, I inserted my first rot key at frame 1, then I went to frame 25 and rotated my empty 180 degrees, then put in my second rot key… the Y axis didn’t give me trouble this time… but the object still wants to rotate on both the Z… and the X.

This here is the link to the new file with which I ended up.

http://www.geocities.com/cronocat0/wrongax.zip

You have to set your second keyframe at less than 180. Since you are just keyframing the state at an instant of time you aren’t giving the program enough information (there are an infinite number of shortest distance rotations to get to the new position).

Place your second keyframe a 90 degrees at say frame 12 and a third at 180 degrees on frame 24. Or you could just edit the ipo curve.

GreyBeard

Your blend file fixed up:
http://members.shaw.ca/rjplus/impropernew.blend