The key here is the mia_light_surface utility and of course final gather. May sound complicated but trust me… its very very simple!
Alex from Greensoda with a very interesting quick tutorial on creating the ever-poular (again) Tron like glows using mental ray and connecting a mia_light_surface node to a mia_material_x, which provides some surface shading information as well as a glow from a Final gather contribution… really cool! Check out the comparison from an ordinary surface shader.
Its important to always find great reference for your work in general, but in the areas of glows and lens fx this is even more imperative – a while back Atomic Fiction had a really great post on glows as seen by our minds eye, verses glows as seen by hard reference… the differences are miles apart. Check out the Atomic Fiction Post on Glows from reference.
After posting the tutorial on Vimeo, someone asked what the difference between using this and a surface shader would be. The second image explains what I mean by the geometry looking flat when using the surface shader. “