What would be a way to create a glow in Blender. For that purpose I've been always using the compositor. However, that is pixels work, which means it is a 2d work. To make a 3d one, do I have to use particles, nodes or maybe some simulator? Here is what I mean (If we assume that the blue color is a glow, it is clear that like other objects it has depth) -

My aim is to create lightsabers, among other kinds of glowing effects. the kind of a glow that fades out of the object -

And if possible, how to make one in cycles (not sure if linking objects/scenes would be a way to go, but I want the glow to fit the environment with light bouncing and such.. )?