Q:

How to combine objects in a rendered scene with and without bloom effect? 

I'm working on a game and engine as I go under OpenGL. 
I've had a bloom effect in place for a while that works as a post-procesing effect on the entire screen.  It's been fine up until now.  
I have an object that is made up of a few meshes, and one of these meshes is mostly white.  The result is it blooms like crazy, but I really don't want it to. 
The only way around it I can see is that the objects I do want to have bloom would need to be rendered to a bloom-framebuffer from which I can bloom (and store the depths) to then mix back in with the rest of my scene. 
Is this the only way to go about it?  It seems like a lot of work to simply isolate something from a screen-wide affect. 

A:

Usually bloom is done with HDR rendering where you use a floating point (usually 16 bits per channel) texture for rendering to. 

Things that are brighter than 1.0 get bloom applied. 
Things that are 1.0 or less don't get any bloom. 

You render everything to the same texture, and remove anything that's not bright enough to bloom when you start processing the bloom post effect.  That means you can have a white thing that doesn't bloom by rendering it as RGB(1.0, 1.0, 1.0) and one that does by using say RGB(2.0, 2.0, 2.0). 
http://en.wikipedia.org/wiki/Bloom_%28shader_effect%29
http://kalogirou.net/2006/05/20/how-to-do-good-bloom-for-hdr-rendering/

