[osg-users] Multiple Render Targets - Request forComments/Testing

[J.P. Delport]

Hi Art,

Art Tevs wrote:
> Hi J.P.
> 
> I am also using MRT, however completely without
> osg::Camera.
Yes, I've compiled osgPPU and ran the examples; cannot say that I fully 
understand the code yet :)

> 
> However since I am working with FBOs directly I would
> prefer to have something like an extra StateAttribute
> or something which should setup the MRT. Or maybe the
> setDrawBuffers as an extra method in the FBO code.
> 
> I think having the MRT (enable/disable) as a
> StateAttribute would be the more general way. However
> this would probably require some extra changing in the
> RenderStage or wherever to detect that extra
> StateAttribute. 
> 
> What do you think, guys?

I think having the MRT selection going through FBO-class could be a good 
option. However, I do not know how to add the StateAttribute. We might 
need an enable/disable and setDrawbuffers, or can a StateAttribute take 
a vector? I do not know how to pass the vector of render targets using 
an attribute?

-----

At the moment I have:

Camera->setDrawBuffers(vec) - this sets the intention to use MRT and 
also passes the list of targets.

RenderStage->runCameraSetup - this queries the camera for the buffers, 
and if there are any, creates a vector of GLenums.

RenderStage->drawInner - The existence of the target vector is used to 
determine if MRT is enabled. glDrawBuffers is called using the vector.

-----

I think what you propose is:

Camera->setDrawBuffers(vec)

RenderStage->runCameraSetup - since this creates the FBO anyway, it 
might as well pass the camera settings regarding MRT to the FBO. Maybe 
using _fbo->setDrawBuffers.

RenderStage->drawInner - instead of checking the member _drawBuffers, 
query the FBO to determine if MRT should be enabled and also get the 
list of targets from the FBO.

-----

This could work, and I can probably integrate it into the patch, but I'm 
not sure how you get your FBOs into renderstage at present.

Also, how do you control the reading back of textures/images? At the 
moment the readback attachment map is also setup in camera. Would this 
also need to be moved?

> 
> 
> Cheers,
> Art

rgds
jp


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