Hi Bernd,
On Thu, 2004-04-01 at 09:58, Hentschel, Bernd wrote:
> Hi again,
>
> Thanx for the immediate help first. The projection works just fine
> now.
OK, good.
> But here is a follow-up:
>
> >sorry to reply myself, this assumes you do not do or simulate
> >head tracking using the user field of the decorator.
>
> so that's basically a problem. Right now, I'm not doing headtracking
> for simplicity reasons but it's the next thing on my agenda. So just
> for clarification (...since the docs are pretty thin on this one):
> What is the viewer node supposed to be for, anyway. Since in the
> tests/examples it is added right below the camera beacon, I assumed
> that it basically gives the offset from the headtracked point of view
> (...which I would set to be the position of the camera beacon) to the
> actual eye position. Is that wrong?
Yes and no. In general most head-tracked environments are bigger than
the actual environment that you can move in. So you still need a way to
move your little part of the world that you are tracked in around, just
like a standard application. For consistency reasons, that's what the
camera beacon is used for, so you can do all the things you do on a
desktop, and they will affect the head-tracked environment in a logical
way. The effect of the actual head-tracking is communicated via the
Decorator's Viewer. The viewer is an independent coordinate system, that
defines the position and orientation of the actual head, which is used
to calculate the eye points' positions and consequently the projection
parameters.
The typical setup is that used in the testProjection program. You have
the standard camera beacon, and the viewer as a child of that. This
makes all transformations of the viewer relative to the camera, and
allows you to directly use the head tracker's data for the viewer's
transformation. Then you only need to specify the projection screen in
the tracker's coordinate system (by measuring the corner's using the
tracker), and you're done. Copy the tracker data to the viewer's
transformation every frame and use the camera's beacon to move around
the world.
Hope it helps
Dirk
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