Long sun world

[chipsidale]

I've been trying to visualize the Long Sun Whorl from the Long Sun cycle books by Gene Wolfe. Not being good at that I'm trying to do this in a 3D program.

The Whorl is a cylinder I estimated (I can be far off) to 40 km diameter and a length of 200 km. The sun that illuminates it is a long cylinder I thought to be ~100 m diameter in the center of the cylinder.
I've tried to do this by a displacement shader (along vertical) using circle's ecuation sqrt( r^2 - x ^ 2 ). I've succeeded doing this with the lower part of the cylinder ( r - sqrt( r^2 - x ^ 2 ) ) but I don't know how to add a new terrain which can be displaced independent of the first one (by the formula r + sqrt( r^2 - x ^ 2 ) ).

I've attached the Terragen file and a rendering picture.

Maybe there are also other ways to do this? (maybe with an external cylinder on which a terrain would be projected?)

Thank you in advance for your ideas

[cyphyr]

This sounds very much like the EON books by Greg bear. There was a competition a year or two over on CGTalk forum to illustrate the hollowed out cylinder world (dimensions look similar to yours). Take a look over there, there were some awesome (and not so) renders some using TG. It should be possible in TG but I'm certainty's not the one to ask. The hardest part I would think would be the atmosphere and cloud settings. These would have to be the reverse of every other 3D app out there with the thickest part of the atmosphere both at ground level and beyond the "long sun" on the opposite side of the cylinder.
Good luck with this one I have been waiting to see a truly convincing cylinder world render.
Richard