I'm fairly new to Java and quite new to Java3D so this may be a fairly simple question, but I haven't had much luck with it. I'm working on a robot simulation where the robot is represented using the D-H convention...which basically means that each joint has its own coordinate frame and joint i rotates about the z-axis of joint i-1. I had thought that if I took the transform representing the axis of rotation (which is passed to the rotation behaviour) and rotated it 90deg about the X axis, the motion would then be about the Z axis and all would be well. Such is not the case. The motion is about the z-axis, but in rotating the transform it flips the rest of the robot 90deg as well...So instead of an upright robot rotating about the Z axis of joint 1, for example, I have a robot lying on its side rotating about the Z axis of joint 1, which just won't do. I don't understand why it does that, but I can hardly claim to understand how the rotationInterp. behaviour works. My question is this: can I change the axis about which the interpolator rotates without changing the orientation of everything in the sub-graph (the rest of the robot)? Solutions I've come up with are to write my own behaviour, but I'm not sure where to start, or caluculate the joint-link parameters of the robot using a representation that rotates about the Y axis, which I would have to learn how to derive....not that learning is a bad thing, I would just like to find an easier solution. Thanks, Andy Trent ===================================================================== To subscribe/unsubscribe, send mail to [EMAIL PROTECTED] Java 3D Home Page: http://java.sun.com/products/java-media/3D/