Robert
Out of interest, when on a terrain (view height 2m) what points of the
terrain grid rectangle (say 50m x 50m) that you are "stood" on are used
to determine culling. The middle or corner points - it's possible that
all five could be outside the view frustrum? I ask because it appears
this rectangle is sometimes culled although part of it is visible.
Regards
Alan Harris
Robert Osfield wrote:
Hi Gert,
I presume these data is a geocentric databases, i..e it has the
curvature of the earth built into it. For geocentric databases osgdem
use the osg::ClusterCullingCallback to cull backfacing tiles. In this
instance it looks like the set up of the ClusterCullingCallback is not
correct.
One way to double check to see if ClusterCullingCallback is at fault
is to disable CLUSTER_CULLING via osg::CullSettings.
If it is cluster culling at fault then have a look at the set up of
the variable. Note, the topmost point won't necessarily be the
problem one that needs to be use to determine the control points, as a
lower but nearer to the edge point might be seen first as you go round
the curvature of the earth.
Robert.
On 4/16/07, Gert van Maren <[EMAIL PROTECTED]> wrote:
Hi guys,
Question about culling/LOD in paged terrains. When a mountain (for
example
a volcano) is on the horizon, it gets culled when it should still be
visible -> viewpoint close to the terrain. as you navigate up
vertically,
the tile pops back in. It seems visibility/invisibility of the tile is
determined from the middle point but it should be from the highest point
of course.
Have a look at the screendumps. Same location but different elevation.
Volcano is visible at higher elevation but not from the lower one.
http://www.k2vi.com/osg/osgdem_lod1.jpg
http://www.k2vi.com/osg/osgdem_lod2.jpg
Only about 30m in elevation difference.
Any settings that I can change?
Regards Gert
--
Gert van Maren
Head of Research & Development
K2Vi Virtual Reality Software
Data Interface Technologies Ltd
Phone: +64 21 2855581
Email: [EMAIL PROTECTED]
Web: http://www.k2vi.com
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