Hi all,
this is one for the graphics gurus:
In OpenGL Programming Guide page 115:
Sometime, programmers who want a continuously rotating object attempt to
achieve this by repeatedly appliying a rotation matrix that has small
values. The problem with this technique is that because of round-off
errors, the product of thousands of tiny rotations gradually drifts away
from the value you really want (it might even bevome something that
isn't a rotation). Instead of using this technique, increment the angle
and isue a new rotation command with the new angle at each updating
step.
But when one examines the code of e.g. MouseRotator then one can see
that the rotations are done exactly the way which can cause numerical
problems. This problem will also occur if an InputDevice does not
deliver absolute transformation values but relative transformation
values (this may be called continously when not in DEMAND_DRIVEN mode).
Does the mul method in TransformxD or MatrixxD take the above issue into
account ?
Until now I made transformations via changing a translation vector,
direction vector( defined with polar coordinates) and an up vector
(defined also with polar coordinates) and using the lookAt method to
calculate a transformation matrix.
But now I want to take the direction of the Viewplatform also into
account (moving forward and backward, up and down, left and right shall
be done using the local coordinate system of the Viewplatform). Thus I
have to do a coordinate transformation into the local Viewplatform
coordinate system, do my transformations and transform the coordinates
back into the virtual world coordinate system. But how to do this with
polar coordinates ? (Is store vctors in cartesian coordinates -> change
to new coordinate system -> change to polar coordinates -> change polar
coordinates -> change to cartesian coordinates -> change to old
coordinate system an option ?)
Can someone (from Sun ? ) make assure that continous matrix
multiplication over a long period of time is no problem in Java3d ? Then
I would switch to this.
regards
Paul
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