[jmarshall]

Reasonably easy to do half-arsed, tricky to do in general.

The problem is that controlgroups can and are hierarchical, thus you want any effect to apply all the way down the chain and thus combine two or more effects together.

The only way I can see this happening is to:

1. Move to rendering every control to a separate render target.
2. Render that render target to the group's render target.
3. All the way up to the main window.

You may only need the render target at the group level, I'm not 100% sure.

While this adds redirection to the rendering, it does have the bonus that we can store that redirection from frame to frame, possibly eliminating rendering every frame later (eg if the control has not changed). This may be a big plus on some systems.

If you wish to investigate this, the first thing to do is figure out what you need at the control level and the group level to pull it off. For instance, some effects may require the backbuffer as an input (eg to blur whatever is under a dialog).

Cheers,
Jonathan