Hi Paul, well, actually, I'm not exactly rendering directly in eye coordinates (provided I understand what you mean): the sphere should not rotate with the camera (in fact I'm not rendering a sphere: rather points representing stars by the way).
But your idea is very good: until now, I was using something like: gl_Position = gl_ProjectionMatrix * gl_ModelViewMatrix * myModifiedVertexPos; ==> I'm computing the modified vertex position by offseting the gl_Vertex by the camera position in the model frame. Now that you mention it I realize my error must come from the usage of the gl_ProjectionMatrix which is the latest projection matrix computed by OSG (using the initial sphere vertices). I'm not familiar at all with projection matrices computation, but I will give it a try tomorrow :-). thanks for your help. Manu. 2009/4/29 Paul Martz <pma...@skew-matrix.com> > So you are effectively rendering the sphere in eye coordinates. Have you > tried simply projecting the coordinates (in the vertex shader) onto the far > plane and rendering them there? The coordinates will (of course) need to be > between the near and far plane in order to not be clipped, so just > projecting them into that range (and ideally onto the far plane) should do > the trick. > > Paul Martz > *Skew Matrix Software LLC* > http://www.skew-matrix.com > +1 303 859 9466 > > > ------------------------------ > *From:* osg-users-boun...@lists.openscenegraph.org [mailto: > osg-users-boun...@lists.openscenegraph.org] *On Behalf Of *Emmanuel Roche > *Sent:* Wednesday, April 29, 2009 9:28 AM > *To:* OSG Users > *Subject:* [osg-users] frustum culling in shader > > Hi everyone, > > Just again a simple problem I can't solve myself: > > I have an sphere object I want to use as a sky sphere. What's the best wait > to do that ??? > > The idea I came to is to use a vertex shader to offset each of the sphere > vertex by the current position of the camera in the model frame. But then > nothing is displayed because the moved vertices are behind the near plane > and are culled :-( > > Any idea ? > > I guess I'm not the first one trying to render a sky sphere any way ?? > > thanks for your help. > > manu. > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > >
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