Here are 19 models for you to try (two rings and 17 planetary-like nebulae) :

http://fsgregs.startlogic.com/Public_Fi ... ebulae.zip (1.9 MB)

Preview of four of these models (mostly "Rosette-like") :

nebulae.jpg

I can generate very easily an **

**industrial quantity**** of these models with lots of variations (there are about 13 parameters to adjust). I haven't found yet the "great" parameter set, which generate "the" nebula :

1. Total number of sprites,

2. Color of sprites,

3. Transparency of sprites,

4. Internal radius of ring or spherical shell,

5. External radius of ring or spherical shell,

6. Thickness of ring or oblateness of spherical shell,

7. Minimum size of sprites,

8. Maximum size of sprites,

9. Two statistical parameters for the distribution of sprites in space (

*Beta* distribution),

10. Two statistical parameters for the distribution of the size of sprites (another

*Beta* distribution),

11. An index parameter for the way the sprites size is increasing over distance...

Wewh ! I don't know how to proceed with this huge parameter space !

You can try editing the color, transparency and the PNG file used in the CMOD file to achieve various effects...

"Well! I've often seen a cat without a grin", thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!"