Hi Torben,
I have replied on the osg-user list rather than submissions, hope that's ok.
I cant say exactly what Roberts plan for optional layers was / is but I can
tell you how I am using them.
Optional image layers have their images stored in a separate directory
structure from 'normal' layers. For example, when not using optional layers,
all meshes and images will be stored in a directory structure such as:
root/
earth.ive
earth_root_L0_X0_Y0/
earth_subtile_l_X0_Y0/
If you then add another 'normal' layer, no new files or folders are created,
the new imagery is just included (by default) in the existing .ive / .osgb
files. When you add an optional layer, all the new imagery is stored under a
separate directory. In the case of the above example:
root/
earth.ive
earth_root_L0_X0_Y0/
earth_subtile_l_X0_Y0/
MyOptionalLayer/
earth_L0_X0_Y0_l1.dds
etc
I am not sure exactly how loading layers is handled by the default Terrain
Technique (I am using a custom one) but one big advantage I gain is that it
allows me to load optional layers on demand. If all the imagery for a layer is
contained in a single .ive / .osgb file, then this must be loaded as one,
regardless of wether all the layers are actually being displayed. With the
optional layer approach, it is possible to only the load the imagery that is
currently being viewed. This is important for my project as our clients can
often have a low bandwidth connection to the map server. This enables us to
make a large number of layers available without effecting the load time of the
base tiles.
My standard setup for VPB generated databases is to only have one 'normal'
layer with data such as blue marble. This acts as the default layer that is
always available. All other imagery layers are added as optional layers.
I hope that makes some sense.
Cheers,
Brad
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Torben
Dannhauer
Sent: Thursday, 1 July 2010 2:46 PM
To: [email protected]
Subject: Re: [osg-submissions] Fix for adding / removing layers / optional
layers using VPB
Hi Brad and Robert,
thanks for your fixes.
One question: can you explain me what optional layers are? ;)
Thank you!
Cheers,
Torben
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=29568#29568
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