Hello Erik,
Erik Podetti wrote:
> Hi everybodies,
> I'm implementing some deferred shading algorithm
> plus Radiance Shadow Maps techniques. What I do now is render the scene
> from the camera point of view in a FBOViewport and draw to multiple
> render targets. Obtaining 3 textures with the scene geometry (1. color
> 2. position 3. normals and linearized depth) next I do following
> render passes adding these textures to a ChunkMaterial and adding the
> Material to a PolyForeground object. In the material I also add a
> SHLChunk with my shader programs. Finally I push the PolyForeground to
> another FBO and render the FBO.
hm, I suppose it is not an option for you, but IMHO this type of thing
becomes a lot less messy with 2...
(I've actually a partially implemented deferred shading node core and
pieces to compute shadow maps for it that I hope to finish in the near
future).
> 1. As I don't need the standard pipeline to render the depth buffer in
> the last FBO can I disable it in any way?
it looks like there won't be a depth attachment if none of the textures
have a depth format.
> 2. Actually I do render 5 or 6 FBO for my render passes in sequence and
> I use these commands in "display" function
>
> win->activate();
> win->frameInit();
> osg::RenderAction *rAct = osg::RenderAction::create();
> fbo->setParent(win);
> rAct->setWindow(win.getCPtr());
> fbo->activate();
> fbo->render(rAct);
> fbo->setParent(NullFC);
> win->frameExit();
> delete rAct;
>
> ...where "win" is the simpleSceneManager window. Is it the fastest way
> I can render FBOs or deleting and recreating render actions is a waste
> of time?
yes, you can keep the RenderAction around throughout the application
runtime.
> 3. I can't figure out why my frame-rate drops down so quickly as I
> render more FBOs...I use OpenGL High lever shading language (GLS) for my
> vertex and fragment programs. Maybe they aren't so optimized as ARB
> programs...dunno...Do you have any experience using those programs?
I suspect it is the way the FBOViewport works, it essentially
reassembles the FBO each frame instead of only when attachments or sizes
change. AFAIUI that is considered a fairly expensive operation.
From my (not exhaustive) experience with GLSL I've not noticed huge
performance problems.
Cheers,
Carsten
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