flapping sea plane

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Harry van Stedum (stedum%indigo-8++at++mscn.nl)
Mon, 14 Nov 1994 15:00:46 +0100


Hi all,

I have the following problem:

I'd like to have a textured sea-plane in a scenery; instead of the
non-textured static Performer Ground plane, part of the pfESky model, with
Multigen, a large plane is put in the XY-plane, with a texture mapped;
the plane is 40 * 40 kilometers.

The problem is that while sailing in the scenery, the plane seems to move
up and down slightly (a few pixels), quickly and irregularly.
(kind of flapping up and down).
   It is especially visible where the sea-plane cuts other geometry; the first
thing one can think of is a zbuffer-resolution problem; but the plane
is drawn the same way as the static pfESky plane, with a zfunction( ZF_ALWAYS )
in a pre-draw callback (or pfClear( PFCL_MSDEPTH) if multisample mode enabled)
 (restored in post-draw callback). Also it's the first node to be
encountered when traversing the Flight tree.

The problem also occurs if the plane is viewed with Performer perfly;
if the far-clipping slider is moved back from 80000.0 to 4000.0, with still
most of the sea-plane visible, it gets better: there's less flapping; this
may be an indication.

The state of several attributes (texture off, lighting off, wireframe on) does
not have a positive effect on the problem; it does not depend on these
attributes.
   I sailed this static sea on VGX, RE and RE2 machines and the problem shows
the same on each system.

Any help on this is greatly appreciated.

Thanks,
Harry

-- 
----------------------------------------------------------------------
Harry van Stedum                                 Simulator Development
Maritime Simulation Centre the Netherlands       Email: stedum++at++mscn.nl
van Uvenweg 9, Wageningen                        Phone: +31 8370 79964
P.O. Box 90, 6700 AB, Wageningen                        +31 8370 79911
the Netherlands                                  Fax:   +31 8370 79999
----------------------------------------------------------------------

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