Hi, Ramy
Sorry for late response (Excuse: Terribly Busy). Truth is I do not have much
to suggest in your case. I have tried with J-S to investigate the problem
of massive flicker when non zero MinLightMargin was used.
This is the observation I got then: When View (shadow receiving) volume
clipped by maxFarPlane gets much smaller than volume casting shadows (made
by extruding first volume by MinLightMargin ) lispsm algortim can get really
badly conditioned numerically. In such worst case Lispsm can produce
projection matrix which has almost 180 deg of FOV. Such matrix does not
only loose lots of mathematical precison, but also makes use of only a small
fraction of shadow texture for shadowed view and this cause the flicker.
But you metnioned that you use small minlightmargin value, so this may be a
different problem. You may also notice similar problems with duelling frusta
case and all techniques are vulnerable to this case producing worse results.
Besides, LispSM may be not particularly well suited for walking / driving
sim. If thats the type of your app you probably should consider PSSM. Some
day I will maybe contribute TrapezoidalShadowMap (but its not going to
happen in next few months I am afraid). Tsm may be better suited for low
moving camera than LispSM but it will still be far from perfect.... PSSM is
usually considered to be most universal technique with reasonably
controllable shadow quality. However, I did not used this technique myself
so I cannot delve into its details.
Cheers,
Wojtek Lewandowski
From: Ramy Gowigati
Sent: Tuesday, March 15, 2011 8:13 PM
To: [email protected]
Subject: Re: [osg-users] ViewDependentShadow massive flickering problems
Hi,
Sorry guys, I know this thread hasn't been active for quite sometime, but I
am also using LightSpacePerspectiveShadowMapVB and im getting flickering and
artifacts. To be honest I kinda got lost in the replies as to how to fix the
flickering and artifacts.
I also have a large outdoor scene and used LightSPSM for my shadows. Shadows
on some buildings are stable, but on others it flickers very fast. my scene
is almost 1Km x 1Km more or less.
I set the near light distance to something small and far distance to some
distance beyond the camera, but not too far in the distance (since its a big
scene).
Reading the thread topic I knew this was my problem also, but I am lost in
the replies. Any clarifications please? If it helps I'm using OSG 2.8.3.
Thank you!
Cheers,
Ramy
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=37634#37634
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