I had this:
what I really wanted was this:
I was setting my vertex size to be the size of an array of vertex structures that had four vertices in them, rather than the size of the structure itself. Because of this, I could only manipulate the location of the first vertex.
But now on to new problems. Right now, it seems like I'm getting a slew of garbage in my glow texture.
Here's a pic:
As you can see, the glow seems to be rendering, but I'm starting out with a lot of crap in my glow texture. Also, I'm not clearing my glow texture on each pass so it ends up eventually filling entirely with color.
I better get back to work.