This is a slightly improved version of POVRay 2.2. I found snowcode.c on 
ftp.povray.org and added the snow function to the source code of POV.

The following lines are taken from 'snowcode.c':

This is the patch code for a snow function for POV-Ray. It's a part of the
"frame", like fog. It has the following visual properties:

	(1) Snowflake size is always 1 pixel. 
	(2) However, smaller snowflakes are simulated by 'antialiasing';
	   they are not completely snow-colored but share some background
	   color.  If I say so myself as shouldn't, this looks good :-)
	(3) The probability of a pixel being changed by a snowflake takes
	  into consideration that a pixel represents a cone which is more
	  likely to include a flake as it recedes. Strictly,the sqrt below
	in the First_Flake computations ought to be a cube root, but it
	doesn't seem to matter much. Change it if you like.
	(4) You can declare distance (essentially number of flakes) and
	flake_size independantly. Typical flake_size is 1.0 - 4.0. 
	(5) This, like crand, is random-number driven. It won't animate
	worth a damn, but looks pretty good in stills.
	(6) This is basically 'near-field' - it does the part of a cloud
	of flakes that is visible as single flakes. You may wish to add fog
	for the flakes that are too far away to see individually.
	(7) Try using this for dustmotes, mosquitoes, etc... anything tiny
	and in the air.


	SYNTAX:  snow{distance 10.0 flake_size 2.0 color White}


ACKNOWLEDGEMENTS: This little piece of code wouldn't run without the great
stuff written by the POV-Ray team. I am really grateful for the opportunity
to use the product of their efforts.  If this code,or any part thereof, is
of any use to the POV-Ray team, they are welcome to use it in any way at
all.
