Hi Gath,

I use osgShadow (VDSM) and osgEphemeris in conjunction, and they seem to 
work together.
However, there are known problems related to osgEphemeris which are 
broader :

- The Skydome in osgEphemeris can be very large, causing unwanted 
interaction with culling/ nearfar planes.
 see 
http://lists.openscenegraph.org/pipermail/osg-users-openscenegraph.org/2009-April/026772.html
long thread, but with useful hints towards solutions
 - I remember problems with clearing operation, but probably related to 
solutions to the previous problem.

If the only thing that you want is a skydome, osgEphemeris is an overkill 
for that.
You probably still have to consider the culling problems introduced by 
skydomes (a scene with a skydome is artificially big).

      Luc



De :
Garth D <[email protected]>
A :
OpenSceneGraph Users <[email protected]>
Date:
05/04/2012 15:34
Objet :
[osg-users] Using osgShadow with osgEphemeris (or alternatives)
Envoyé par :
[email protected]




Hi everyone,

In OpenSceneGraph 3.0.1, is there a known fundamental incompatibility 
between osgShadow and osgEphemeris (circa 4/4/12)? I am using osgShadow 
(namely ShadowTexture), with both animated and static models, and 
started to work in osgEphemeris in order to provide a more interesting 
sky than a single static colour.

One thing I noticed is that whenever osgEphemeris is working, the 
location of cast shadows shifted around significantly, and they are 
nowhere near the objects that are casting them (ie. the shadows were 
very clearly incorrect). Depending on the view angle, they also bounced 
around to different locations. I noticed that animated models no longer 
cast shadows, but that may have just been a symptom specific to my 
particular case.

In case the node mask was causing a problem (for osgShadow I am using 1 
to cast, and 2 to receive), I tried different values. Setting it to zero 
caused the EphemerisModel to vanish (is this normal?), and to four left 
it there, but didn't help the shadow situation. In any case, when the 
EphemerisModel was working, the shadows were shifted around and incorrect.

I've tried disabling lighting on the model (via state sets and 
GL_LIGHTING), as well as attaching it to different nodes, but I don't 
seem to have struck upon the correct combination.

Interestingly enough, if I use either on their own, they work fine. 
Shadows work fine, without ephemeris models; and ephemeris models seem 
to produce good results if I turn off shadows.

Can anyone suggest any things to try, confirm there are known problems, 
or otherwise?

On a side note, I began to investigate osgEphemeris in the first case as 
I needed a simple sky. My requirements are pretty low, as the sky is 
merely decorative, so I don't necessarily *have* to use osgEphemeris 
specifically. I am wondering what the best approach to sky creation in 
OSG 3.0.1 would be? The potential solutions I ran into were:

- Use the sky code osghangglide as a base/inspiration.
- Find a spare $1.5k and use SilverLining (a bit overkill for my 
application at present!)
- Use "skydome.osgt" from the OpenSceneGraph data dir (I gave this a 
shot, but I wasn't able to successfully get it working correctly with 
the rest of my app)
- Build up my own geometry, customising the texture coordinates as I 
need (the most flexible approach, but the most time consuming, and the 
most pointless if someone has done it already), and grab or buy some 
existing sky textures to match the expected texture.
- Use osgEphemeris, which is what I'm looking at above.

Are there other solutions that I should be exploring as well, or in 
preference?

Garth

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