I am importing vehicle dynamics data from an excel file. The data specify the X, Y, Z, roll, pitch, and yaw position of the vehcile body, and X, Y, Z, steering angle, and rotation for the tires. It is assumed for the sake of these data, the tire “roll”, or camber angle, is constant and parallels the vehicle body roll angle. Thanks to some big help (thanks Al) the script is working and when I import a keyframe at each animation frame, the animation works fine. However, there are a couple of nagging problems:

1. When I scrub the animation by hand in a viewport, the wheel motion is fine. But when I play it, I get some incorrect wobble and other rotation in the tires (which does not render thankfully). If I set the keyframe tangents to step, the viewport play looks fine. I am just wondering why the weirdness when I play it, but not when I manually scrub or render the animation.

2. This is the big problem. There are occasions when I will not want to set a keyframe at each frame. That is, instead of capturing data at 1/30th second intervals, I want to capture the data at 1/3 second or 1/2 second intervals. The script handles this with no problem and sets appropriate keyframes and the position and rotation of the vehicle and tires exactly matches the data in the 1/30th second data set, so I don’t suspect a problem in the script. BUT, between the keyframes at the 1/3 second capture, the tire rotations go berserk. I tried all sorts of keyframe tangent combinations, but the tires rotations go nuts. Why? Is there a fix?

I’m attaching two scenes. One with a keyframe at each frame, that is 30 keyframes per second and one where there is a keyframe every 1/3 second, 3 keyframes per second. There are no copyrighted objects or information in the files. Unfortunately, I can’t provide the script itself as it is “private”.

EDIT 1:

Thinking about this, I’m more convinced both of these problems are the same problem. When I “play” the 1/30th second animation, I’m seeing some between frame interpolation problems which disappear when I scrub manually. When the keyframes are further apart, this bad interpolation is visulaized as thses between data are rendered. I hope this makes sense.

EDIT 2:

I strongly suspect it is in how 3ds is doing the rotations. Is there a way to coerce 3ds to apply interpolated individual rotations in a specific order and coordinate system? For example, I want the X, and Y axis rotations to be interpolated and applied in the world frame, but the Z axis rotation to be in the local frame.

David

David

Collision Forensics & Engineering, Inc.
http://www.CFandE.com

	Attachment
scenes.zip