i had the same issue a while back but i never found a solution. whats the protocol for masking out the fire and or smoke so i can give it a filter, in my case a fog glow. in this simple mock up with suzanne i want to keep them and the smoke on the same render layer.
so if i want to apply a filter only to the flames then i need to find a way of isolating it. you cant add a material pass to the smoke doman because that will apply it to the actual shape of the domain instead of the voxels. i tried using a chroma key and set the key colour similar to the fire but it did a poor job at only applying it to the colour i wanted. besides this method even if it did work would be bad in a more complex scene with a broader colour range. so please what can i do im running out of ideas?