I am trying to create a bloom effect around my emission map using the glare node in compositing. The problem is that my emission map isn't bright enough for this to work. I don't want to increase the emission map's strength, because it washes out the detail.
What I've done is to multiply the value of the emission map, run that through the glare node, subtracted the brightened emission map from the result, and max/lightened the result over the result. The problem is that the subtraction isn't perfect, and it results in this black edge:
Is there a better way to go about doing this? I'm hoping for a way that doesn't require separating the emissive part of the mesh as a different object, because often the emissive parts won't be on isolated geometry from the non-emissive parts, if that makes sense.