In "fancy" graphics, the glow would be around some particles...
maybe have a vis. mode that bevels it or something?
EDIT:
Blob Mode.
Exactly :D
So, imagine someone throws a ball at you. From your perspective, you see it getting bigger as it approaches you. The person who threw the ball sees it shrinking as it moves away. If it were a lightbulb being thrown, it would get brighter as it approached you, and dimmer for the other person.
Now, imagine you are a pixel on the screen of the TPT window. A lava particle moving towards you would get bigger and brighter as it moves, like the lightbulb, but this time, only in 2-dimensional space.
In 3-d space, which we live in, we see in 2 dimensions- like pictures, which have the ability to capture events happening in 3-d space. Likewise, taking it a dimension down, 2-d space, in which the pixel you are viewing from exists, would see in one dimension, a straight line.
You get it?
I can't code in C++.
Okay, here's a half-decent picture I just made.
This ignores brightness.