Hello Daniel,
Daniel Weber wrote:
> I tried to implement pseudoinstancing(drawing the same geometry many times
> and transform it in the vertex shader). I wrote my own nodecore, derived from
> MaterialDrawable, and used the techniques from Particle nodecore. My first
> version used immediate mode, which worked fine but was too slow for my
> purposes.
>
> Therefore I want to use vertex buffer objects, which should be updated when a
> new geometry is attached. The Geometry and Particle core use very complicated
> mechanism to get this working and I didn't get through it.
>
> - Is there a simple way to use vbos?
> - When and where do I setup the vbos?
ok, let's see if we can narrow down the problem a little. The main
complication normally comes from the fact that you can not make OpenGL
calls from arbitrary places as the code may run in a thread that does
not have an OpenGL context.
Most objects that deal with OpenGL state therefore use GLObjects to
delay updates of the state until the render thread needs it. The way
this generally works is (cf. OSGGeometry.cpp):
- in onCreate you register (registerGLObject) an update and a destroy
handler function with the Window
- in changed you mark the GLObject for a refresh or reinit
- in the registered update handler (handleClassicGL/handleAttGL for
Geometry) you make the necessary OpenGL calls to update the OpenGL object.
- in the registered destroy handler you free the OpenGL resources
Geometry has two update/destroy handlers because it needs to call
slightly different functions depending on whether fixed function
pipeline or generic vertex attributes are used. Normally one is sufficient.
> - What do I have to consider to make this work across different aspects?
it should work with the above setup.
Cheers,
Carsten
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