BEGIN {
particles	= 2000		# number of flakes
startSnow	= 0		# starting frame
falling		= 50		# no. of frames a flake is falling
x_shift		= 0		# higher value means stronger wind
z_shift		= 0		# higher value means stronger wind
variation	= 20		# max. variation from the mean path
ground_level	= 5		# Y coordinate of the ground
x_origin	= 0		# birth area location 
y_origin	= 160		# birth area location 
z_origin	= 0		# birth area location 
x_length	= 300		# birth area x-length
y_length	= 0		# birth area y-length
z_length	= -200		# birth area z-length
   
    # initialise the random number generator
    srand()

    for ( i = 1; i <= particles; i++ ) {
	# define the object
	object = "object01"
	printf( "  objectelement { \"eobject%d\" \"%s\"\n", i, object )

	# generate the position
 	x = x_origin + (x_length * rand() - 150)
	y = y_origin + y_length * rand()
	z = z_origin + z_length * rand()
        
# place the object in position
printf( "    loc { (%f %f %f) }\n", x, y, z )

# create a track
printf( "      controller { \"position\"\n" )
printf( "        track {\n" )

 	# generate first frame
startFrame = startSnow + int(144 * rand())

	# start frame
printf( "          pointkey { %d (%f %f %f) (0 0 0) (0 0 0) \"?\" }\n", startFrame, x, y, z )

	# generate end frame position
	x = x + x_shift + variation*(rand()-0.5)
	y = ground_level
	z = z + z_shift + variation*(rand()-0.5)

	# end frame
printf( "          pointkey { %d (%f %f %f) (0 0 0) (0 0 0) \"?\" }\n", startFrame+falling, x, y, z)

# close the track
printf( "        }\n" )

# close the position controller
printf( "      }\n" )

# the visibility controller
printf( "      controller { \"visibility\"\n" )
printf( "        track {\n" )

# initially invisible
if (startFrame > 0) 
            printf( "          booleankey { 0 0 \"?\" }\n" )

	# to avoid phantom-key problem
	if (startFrame > 98)
            printf( "          booleankey { 98 0 \"?\" }\n" )
	printf( "          booleankey { %d 1 \"?\" }\n", startFrame )
     
# to avoid phantom-key problem
	if ((startFrame+falling) < 98)
	printf( "          booleankey { %d 1 \"?\" }\n", 98)

# close the track
printf( "        }\n" )

# close the visibility controller
printf( "      }\n" )

# close the object element
printf( "    }\n" )
      }
}