One snow

; one piece of snow coming down from 30 meters above
; By Andy Yeh
CS RESET
SETBG 29
SETSCALE .05 .08 .05
SETDC 880 880 880
SETEC 700 700 700
SETSC 930 930 930
SETAI 66
SETSH 540
SETTR 0
RECTANGLE
MAKE "snow OBJECT ; create a variable :snow with value the current object id.
; whenever there is an object created, the keyword OBJECT will store its id.
; :snow will be used later for animation
MAKE "poskey [] ; make a variable :key as an empty list
MAKE "poslist [] ; make a variable :poslist as an empty list
MAKE "orikey [] ; make a variable :key as an empty list
MAKE "orilist [] ; make a variable :orilist as an empty list
; collect key values. Keys should be between 0 to 1
; repeat to collect value because sometimes I need more values between 0 and 1
; the keys can be different intervals.
QUEUE "poskey 0 ; queue first value in key list
REPEAT 4 [
QUEUE "poskey REPCOUNT / 4  ; queue is a command to add a value to the end of the list
]
QUEUE "orikey 0 ; queue first value in key list
REPEAT 12 [
QUEUE "orikey REPCOUNT / 12  ; queue is a command to add a value to the end of the list
]
; to collect position values, simply move the turtle around
; the command pos will return the turtle's position/location
UP 30
QUEUE "poslist POS ; queue current position as the first value in :poslist list
DN 5 QUEUE "poslist POS ; second value
DN 10 QUEUE "poslist POS ; third value
DN 15 QUEUE "poslist POS
; fourth value, I only go east 1 because this will create different speed effect.
QUEUE "poslist POS ; fifth value, back to beginning position
; to collect orientation values, simply rotate the turtle
; the command ori will return turtle's orientation.
QUEUE "orilist ORI ; queue first value of current orientation
REPEAT 4 [ ; use repeat to collect the next 4 values.
RD 90
QUEUE "orilist ORI
]
REPEAT 8 [QUEUE "orilist ORI]
;
; for animation, a timesensor is needed. The syntax of timesensor is
; timesensor name loop_interval_in_second loop_true_or_false
TIMESENSOR "TIME1 30 "TRUE
TIMESENSOR "TIME2 4 "TRUE
; to animate position, we need a position interpolator
; posint name key value
POSINT "pi :poskey :poslist
; to animate orientation, we need an orientation interpolator
; oriint name key value
ORIINT "oi :orikey :orilist
; now we have everything
; we use command route to hook up everything
; route name from_node from_field to_node to_field
ROUTE "route1 "TIME1 "fraction_changed "pi "set_fraction
ROUTE "route2 "TIME2 "fraction_changed "oi "set_fraction
; the above, we use the same timesensor to drive both interpolators
; the fraction_changed and set_fraction are fixed, simply type in exactly as they are.
ROUTE "route3 "pi "value_changed :snow "translation
; since pi is now in action, we route its value to :snow's translation
ROUTE "route4 "oi "value_changed :snow "rotation