Modify frame brightness and contrast

[Dario]

Hello,

I have a system which use a lot of shaders, like osgOcean and osgHimmel.

I would like to be able to regulate the overall brightness and contrast of the final frame. Do that modifying shaders pipeline is expansive and need to go deep in the components pipeline. 

I'm thinking about a post processing at osgViewer frame level. Can you suggest to me a starting point to do that?

Many thanks,

Bye