I've created objects that use the Halo material but it has a vertex glow. How would I make a whole line glow without dividing my surface into an absurdly large number of vertices?
If you want to do this relatively easily and for certain edges, select the appropriate faces in edit mode and click EDIT->Mesh->Faces->Wire Frame on a duplicate of your original model.
Assign new materials with emission. I recommend just doing a solid material and join the models back together (I really usually work in Cycles, and if doing so you can use a simple Emission shader since Blender Internal doesn't really like emitting from materials in my experience). This adds a few vertices, depending on how smooth you want your outlines to be, but I've found that usually they can be pretty simple. You wind up with something like this:
This is something that I saw today that is kind of interesting.
Take your model, and UV unwrap it normally.
Duplicate the UV unwrapping, and click UV Unwrap->Reset on this second UV unwrap (check the far right of the image below and you'll see if you did this right)
Create nodes as follows for your material:
Note that the UV values correlate to R and G above.
This solution adds no extra geometry, and handles subdivision well (if you do it, however, remember to un-check "Subdivide UV" in the modifier or you'll get issues). You can adjust thresholds by moving the Greater Than math functions closer/further to or from 0 or 1.
I mostly based my setup off of this tutorial from TheBlenderNerd (to the point where I even used the same thresholds!), which can be helpful if you want to figure out what exactly I did, or if you run into an issue with forming the UV maps.
Here it is: http://www.youtube.com/watch?v=zjhdGY21WqQ
The solution is different depending upon whether you are using the Cycles render engine or the Blender Internal render engine.
- Cycles: Select your object and go into edit mode. From that screen, select each of the edges you want to glow, then go to the materials menu and assign them an 'emissions' material. This is probably not only the easiest way to handle glow, but also will produce the nicest results.
- Blender Internal: First, duplicate your shape: one of the copies will serve as your object-proper, and the other one will produce the glow. Select one of these, and apply a subsurface division to it. Now go into edit mode and apply loop cuts on every side, sliding them up so that they lie very near to the actual edges of the object. Optimally, you should be able to get these loop cuts close enough to the edge that when you zoom back out and go into object mode, it should look almost as sharp as the original shape. However, by doing this, the other copy of the object should be just peeking through the object along every edge. Select the other shape, and shrink it down ever so slightly (maybe a factor of .995 or so) so that it fits snugly inside the first shape. Finally, you should go to the material menu and assign the inner object a material, then go down to the 'Shading' options and increase the Emission value. If everything is sized properly, then the edges should have a nice glow.
With either of these options, you can always use either the compositor, or an external editing program (like GIMP or Photoshop) to enhance these effects.
A material/texture approach wouldn't be best for this application for the reason you stated, as well as the problem of it not being able to shine light. I would use a combination of a Cycles emission material and compositing to blur the object. This will allow the material to actually shine light; while compositing adds the glowing effect. For a non-glowing fuzzy line, a hair particle system would work in many cases.