David Megginson writes:
> It's in docs/Model/fgfs-model-howto.html.  You have to check out the
> docs module of FlightGear to get it, though, since it's not part of
> the main source distro.  When I have time, I'd like to get it into the
> Wiki.

Ok, I have added a section to this document for the scale animation
type.  (note, it really should be expanded since most of the animation
types didn't exist when it was originally written.)

One possible work around for plib's non-support of the scaling
operation is to build the object at it's maximum size and always make
it smaller.

Plib's view frustum culling scheme works by building bounding spheres
around each object.  It isn't able to compute how a scale operation
will change the effective size of the object (tough problem to be
fair) and so it will do the culling based on the original object size.

This means that if you scale you object larger and the space occupied
by the original object goes out of view, your entire object will
disappear (this is bad.)

However if you start with a big object and scale it smaller, the
scaled version will always live inside the original bounding sphere,
so you will not have the same sort of drop outs ... only a possible
inefficiency since the object could be drawn even when it's smaller
version is entirely outside the view frustum (because the originally
sized object could still be inside the view frustum.)

So a work around at this point would be to build your object at it's
maximum size and then always scale it smaller.

What do you think Lee, can you work with this?

Regards,

Curt.
-- 
Curtis Olson   IVLab / HumanFIRST Program       FlightGear Project
Twin Cities    curt 'at' me.umn.edu             curt 'at' flightgear.org
Minnesota      http://www.menet.umn.edu/~curt   http://www.flightgear.org

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