Put that in your pipe and smoke it.

Here we started with a cube and deleted most of the vertices, then added the usual subsurf modifier as well as a mirror modifier. This mirrored the semicircle shape across the X,Y and Z directions.

The next modifier we added was the array this duplicated the shape and by some slight tweaking it became a 10circle high pipe.
We then added a bezier curve to it and this was mapped onto the pipe. There were a lot of different shapes I could make by changing positions of the verts.

I changed the world background colours and pressed the blend button which gave a nice gradient. It's a lot more interesting than the simple bluey/green window we're always stuck with.