#Great Gas
If you've got Forge and Essence2 there's an easy way to make a
nebula. Start with the cyclone texture and render out a grayscale
image of it. This will be a transparency map. You should make sure
that the cyclone size is smaller than the window so it will have a
completly black background all the way around it. I use no twist for
the cyclone. This gives a nice blotchy cloud. You then make it a
negative with Adpro or similar program. This will make the outer
parts of the image fully transparent and the cloud in the center
semi-transparent. I suppose you could also render the image with a
white background and make the cloud color black so you didn't have to
make the image a negative. Once you have the image you map it onto a
square, flat plane as a filter map. Add some fractal color. (medium
red and dark blue seem to look good) Now stretch the plane in one
direction. (at least 2X on the 'X' axis) This will stretch the image
and give you a more streakish nebula. I've used this system with
LightWave and found that it gives better results than most of the
fog-object Imagine nebulas I've seen.
Note: There was a bug in Imagine 2 that wouldn't render starfields
through transparent objects although It may have been fixed in
Imagine 3.
I think I might have uploaded the LightWave nebula object into the
Amigaarts/3D library. While the object isn't usable with Imagine the
image is a good starting point. (the object is just a flat plane)