Heh, it's funny that the internet has spawned all sorts of unspoken social
norms. For example ALL CAPTITAL letters is shouting, and multiple ?? markes
generally means a rising inflection on the last syllable with a slight
increase in the volume of the tone. Three and four ???? mean a slightly
hysterical edge to the question and often is used to issue a incredulous
declaration like "you say this, how can this be????" This is because you
know the person had to type out four ? and you can picture them hitting the
keys pound-pound-pound-pound while they grit their teeth.
Now that my morning social observation has probably irritated a few people
let me answer the question at hand.
Once you have the transformation from the view platform you can get just the
rotation component of the matrix using methods in the Transform3D. This
will be in radians. Just note that it is a rotation from the (0,0,-1)
direction in a clockwise direction. Personally if I was solving the problem
I would extract the rotation component from the view and put it in a new
transformation, build the "arrow" geometry pointing in (0,0,1) and transform
it using the rotation.
Dave Yazel
-----Original Message-----
From: Quoc Huynh [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, June 13, 2001 6:35 AM
To: [EMAIL PROTECTED]
Subject: Re: [JAVA3D] View Platform FOV Direction
Hi Paul,
okay, i've got the transform and u suggest transforming the
vector(0,0,-1) to work out how this vector maps in 3D space. From the new
vector, I can find angle between the two vectors, and hence find the angle
of rotation about the y axis. Is this correct???. Is this the only way to
extract the rotation angle?? or is there a simpler method. I would just
like to find the angle of rotation in radians. by default the rotation
value is set at 0 (looking down the Z axis) and PI/2 is look looking
parallel to the X axis. I just need to find that theta value for rotation.
cheers,
Quoc.
At 08:51 AM 13/06/2001 +0200, you wrote:
>use the Viewplatform . getLocalToVworldTransform( ) method and transform
>e.g. the
>vector (0,0,-1) the you get a vector you are looking for in 3d space. Set
>Capability
>bits to read the above mentioned transformation.
>
>regards
>Paul
>
>Quoc Huynh schrieb:
>
> > Hi all,
> >
> > I'm trying to retrieve a value from the viewing platform that
> will tell me
> > in which direction the viewing platform is looking. I have a viewing
> > platform moving through a terrain, the position of the viewing platform
is
> > mapped to a 2D image of the terrain, updated with the translation
component
> > of the viewing platform to show its position. Ideally i would like to
have
> > an arrow on the 2D map showing, the direction of the field of view in
the
> > current 3D terrain.
> >
> > Does anyone know how to retrieve this information????
> >
> > cheers,
> >
> > Quoc.
> >
> >
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