Hi Clara,
the problem is, that rtotation takes affect in the local coordinate system.
For example you take a coordinate system with positive x to the right, pos.
y up and pos. z coming out from the screen. Apply rotation counterclockwise
around the y axis. Now, the z axis has the same direction as the former x
axis. If you now apply a rotation around your z axis, it looks like a
rotation around the "old" x axis.
If want to let rotate an object around a coordinate axis and you don't want
to care about its current orientation, you first have to apply its inverse
transformation to set the object into its "initial" orientation. Then apply
your rotiation and transform it back.
Gernot
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http://www.janet.de
Clara Dinh
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Sent by: Discussion cc:
list for Java 3D API Subject: [JAVA3D] x,y,z rotation
and angles
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07.02.00 19:50
Please respond to
Discussion list for
Java 3D API
I've looked through the archives for Java3D and have read the
messages dealing with obtaining rotation angles and quaternions and
matrices, etc. However, from all of that information, I still
haven't been able to fix my problem.
I have a 3D graph, with the standard x,y,z axes and labels.
When I rotate the graph, the labels rotate with it, as they should.
However, depending on the direction of rotation, sometimes the labels
will appear upside down. And I'm trying to resolve this by having
"moving" labels that will always appear in the front and left sides
of the graph (labels will flip accordingly as the graph/cube is
rotated). To do this, I have used various methods to read the rotation
angles to determine which location to move a label to. I can get the
x and y angles of rotation fine but am having difficulty getting the
z rotation angle. For example, if I start off with the standard
orientations
of Y being positive in the up direction, X being positive in the right
direction, and Z being positive coming out of the screen towards the
viewer,
rotating Y by 90 degrees will have me looking at the Z axis on the
horizontal. Now, if I try to rotate in the + or - z directions, it
is the X rotation angle that changes. I got it to work as long as the
X axis remains horizontal but when X goes vertical, it can't tell
the difference between X and Z.
Any suggestions would be greatly appreciated.
Thank you in advance.
-Clara
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