Evan Drumwright wrote:
> Lily,
>
> I need to rotate about an *object's* x,y, and z axes, rather than the
> coordinate system's axes. Unless there is something that I am missing, I
> cannot rotate around x, y, and z simultaneously. I first must rotate around
> one axis, then around another, and finally the third. As I said before, if
> I perform the rotations in the order x, then y, then z, I have to account
> for the y axis being rotated about the x axis, and the z axis being rotated
> about the x axis and then about the y axis...
>
> Evan
>
> -----Original Message-----
> From: Lily Lee <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> Date: Wednesday, January 26, 2000 2:37 PM
> Subject: Re: [JAVA3D] more vecmath questions...
>
> >Evan,
> >
> >I don't understand the problem that you are describing.
> >
> >... and is there any reason that you are applying rotations about each
> >axis sequencially? If not, then the whole idea of using axisangle is
> >to get a rotation about any arbitrary axis, such as [0.2, -0.4, 0.6],
> >that does not even have to unit length, and any arbitrary angle.
> >
> >Lily Lee
> >
> >
> >>
> >> First of all thanks for your help, Lily Lee. AxisAngle is the solution
> to
> >> rotating about an object's coordinate system rather than the absolute
> >> coordinate system...
> >>
> >> However, I am still confused about something. Let's assume I carry out
> >> rotations about the x axis first, then about the transformed y axis, and
> >> finally about the transformed z axis. From my computer graphics text,
> you
> >> multiply the transformation matrix by your vector to get the transformed
> >> vector.
> >>
> >> For example, the matrix for rotation about the x axis is:
> >>
> >> 1 0 0 0
> >> 0 cos a -sin a 0
> >> 0 sin a cos a 0
> >> 0 0 0 1
> >>
> >> If I multiply this by the unit vector along the y axis, [ 0 1 0 1] T,
> then I
> >> get the vector [ 0 0 1 1 ] T, which is the unit vector along the z axis.
> >> This conforms to the right handed coordinate system and makes sense.
> What
> >> doesn't make sense?
> >>
> >> Let's say that I rotate my object around the absolute X axis by some
> >> arbitrary angle. I then should be able to rotate the unit vector for the
> Y
> >> axis by the same angle (we'll call this rotated vector Y'). I can then
> use
> >> AxisAngle to rotate about Y'.
> >>
> >> However, the above doesn't work! I have to multiply my Y unit vector by
> the
> >> X rotation matrix (instead of the other way around) to get this to work!
> >> Things get even crazier when I try to obtain Z'!
> >>
> >> To get Z' I multiply the Z unit vector by the 3x3 rotation matrix of my Y
> >> transform. However, to get this to work, I have to negate the x
> component
> >> of the vector!
> >>
> >> Can anyone explain why this is the way it is done?
> >>
> >> Thanks,
> >> Evan Drumwright
> >>
> >>
> ===========================================================================
> >> To unsubscribe, send email to [EMAIL PROTECTED] and include in the
> body
> >> of the message "signoff JAVA3D-INTEREST". For general help, send email
> to
> >> [EMAIL PROTECTED] and include in the body of the message "help".
> >>
> >
> >===========================================================================
> >To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> >of the message "signoff JAVA3D-INTEREST". For general help, send email to
> >[EMAIL PROTECTED] and include in the body of the message "help".
>
> ===========================================================================
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> of the message "signoff JAVA3D-INTEREST". For general help, send email to
> [EMAIL PROTECTED] and include in the body of the message "help".
hello Evan,
If you want to rotate x,y,z in a static frame in stead of first rotate around
x, the rotate around y in the now x-rotated system, you should use setEuler().
kind regards
Hardy Henneberg
===========================================================================
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff JAVA3D-INTEREST". For general help, send email to
[EMAIL PROTECTED] and include in the body of the message "help".
