Hi Marius,
I am not sure what ECEF acronym means. I guess its WGS84 eliposoid
coordinate system with origin in ellipsoid center.
We are using LispSM with VPB generated terrain. Do you use
setModellingSpaceToWorldTransform method ? It should be helpful in your
work. See example of usage and setting it in osgshadow.cpp lines 832-851
(OSG trunk).
However, I have not tested it with LispsmVB though, but LispsmCB and
LispsmDB. And they seem to work precisely enough most of the time.
When impleneting Lispsm/Minimal Shadow Map algorithms, I made the effort to
make all computations using doubles. At the time when I was doing this,
bounding boxes were based on floats so it may be the case that some issues
could be related to inacurate bounding box precision.
But my observations regarding shadow volume computations suggest different
cause: even double precision is not enough for convex polytope math in WGS84
world coords when these convex polytopes are made from view frustums with
very short near planes. For this case it would be better to make all shadow
volume computations in view space. I wish I could do this someday but
frankly I do not expect it to happen anytime soon.
Cheers,
Wojtek Lewandowski
----- Original Message -----
From: "Marius Heise" <mhe...@heise-network.com>
To: <osg-users@lists.openscenegraph.org>
Sent: Tuesday, December 29, 2009 12:20 PM
Subject: [osg-users] osgShadow & ECEF precision problems
Hi!
I have been using osgShadow::LightSpacePerspectiveShadowMapVB very
successfully in previous osg projects. I am currently making the
transition from a local XYZ to a whole earth ECEF database.
In general the shadow still works correctly, but jumps around by about a
meter or two when my model moves. It looks like the underlying shadow
bounding volume calculation architecture is not completely implemented
with double precision. If so, could anybody give me a hint if the
modifications are simple and where they are?
Thanks a lot - any help is appreciated.
Cheers,
Marius
------------------
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http://forum.openscenegraph.org/viewtopic.php?p=21909#21909
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