My cube doesn't want to glow. (2.70+ cycles, volumetric)

I’d like to make a shape glow (to make it not just to emit light, but to illuminate the volume around it) like this:

So I created a cube, and put a volume (an UV sphere mesh) around it:

To the cube I gave an emission shader, and to the sphere this material:

But all I can see is a white cube without the glow around it.

It’s hard to tell without that final image showing what the render looks like now, but the first thing I would do is play with the density value (it might be too low).

You were right, now I see that if I play with the density and the strength of the emission, I can get it to work, but I don’t find the results too inspiring so finally I made a “fake glow” by drawing a bigger cube around the original and giving it a radial white to transparent gradient that pretty much creates a glow effect and renders nicely also at lower samples.

You can achieve something similar in the compositor. Example:

(I had to use two glare nodes since one wasn’t bright enough)

The emission shader in the material will still illuminate other objects, so once you layer the composite glow over top on the cube-- it should still look legit.

Thanks Murray! I didn’t know about the glare node, but it looks just as so good and this way the glow is created not by a mesh so it won’t interfere with other rays on the scene. So I think I’ll do it this way.