(prompt "\nPlanets_motion by AutoCAD - planets_motion.LSP")
(prompt "\nCommands:  earth_venus_1 earth_venus_1_color earth_venus_2 ")
(prompt "\nCommands:  earth_venus_2_color earth_venus_3_a  ")
(prompt "\nCommands:  earth_venus_3_b earth_venus_3_c  ")
(prompt "\nCommands:  planets_a  planets_b  draw_epi_cycloid ")
(prompt "\n           ")
;----------------------------------------------------------
;;Takaya Iwamoto  Nov 13,2006
;;ref. A little book of Coincidence (Pattern in the Solar system)
;;	by John Martineau	Wooden Books	2001
;;
;;data
;;	Planets		mean orbit(e+6 km)	Tropical year(days)
;;
;;	Mercury		  57.91			   87.968
;;	Venus		 108.21			  224.695
;;	Earth		 149.60			  365.242
;;	Mars		 227.92			  686.973
;;	Jupiter		 778.57			 4330.6
;;	Saturn		1433.5			10746.9
;;	Uranus		2872.46			30589.
;;	Neptune		4495.1			59800.
;;
;;;****planets_motion.LSP
;;;	planets_a	two planets with Sun at the center
;;;	planets_b	two planets with ref at the center and the other
;;;			rotating around the Sun (epi-cycloid like)
;;;executables related to Earth-Venus
;;;	earth_venus_1		Sun at the center
;;;	earth_venus_1_color		..
;;;	earth_venus_2		Earth at the center (epi-cycloid model)
;;;	earth_venus_2_color		..
;;;	earth_venus_3_a			..
;;;	earth_venus_3_b			..
;;;	earth_venus_3_c			..
;;;	earth_venus_3_d			..
;;;
;;;	draw_epi_cycloid
;;;		use  inner radius=40, outer radius = 104, total angle =4680(13 years)
;;;	note:radius ratio = 5/13
;;;		actual data  41.39, 108.21 (earth-venus combination)
;;;			ratio of tropical year = 224.695/365.242 = 8/13
;;;			will make the actual cycle from 13 years to 8.
;;;
;;;main
;;;Sun at the center
;;;Planets_a
;;;
(defun c:planets_a()
	(setup_planets_a)
;;repeat loop
	(repeat n_repeat
		(entdel ref_pos)
		(entdel cmp_pos)
		(setq deg (* step step_deg)
			rad (dtr deg)
			v_rad (* ratio rad)
			pnt_ref (list (* ref_orb (cos rad)) (* ref_orb (sin rad)))
			pnt_cmp (list (* cmp_orb (cos v_rad)) (* cmp_orb (sin v_rad)))
		)
		(make_line_1 "0" 8 pnt_ref pnt_cmp)
		(my_block_insert "yellow_ball" pnt_cmp 5.0 )
			(setq cmp_pos (entlast))
		(my_block_insert "green_ball" pnt_ref 5.0 )
			(setq ref_pos (entlast))
		(if (= ICAD 0) (command "shademode" "G"))
		(setq step (1+ step))
	(command "_.delay" delay_time)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;
;;;Planets_b	reference (observer's) planet at the center
;;;
(defun c:planets_b()
	(setup_planets_b)
;;repeat loop
	(repeat n_repeat
		(entdel ref_pos)
		(entdel cmp_pos)
		(setq deg (* step step_deg)
			rad (dtr deg)
			v_rad (+ pi (* ratio rad))
			pnt_ref (list (* ref_orb (cos rad)) (* ref_orb (sin rad)))
			pnt_cmp (list (* cmp_orb (cos v_rad)) (* cmp_orb (sin v_rad)))
			r_len (distance pnt_ref pnt_cmp)
			theta (angle pnt_ref pnt_cmp)
			cmp_pos_new (polar pnt_s theta r_len)
			theta_s (angle pnt_ref pnt_s)
			ref_pos_new (polar pnt_s theta_s ref_orb)
		)
		(make_line_1 "0" 8 cmp_pos_new cmp_pos_old)
		(my_block_insert "yellow_ball" cmp_pos_old 5.0 )
			(setq cmp_pos (entlast))
		(my_block_insert "red_ball" ref_pos_old 10.0 )
			(setq ref_pos (entlast))
		(if (= ICAD 0) (command "shademode" "G"))
		(setq step (1+ step))
		(setq cmp_pos_old cmp_pos_new ref_pos_old ref_pos_new)
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" delay_time)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;SETUP_planets_a
;;;
(defun setup_planets_a()
	(setup_sysvar)

;;Radii of two planets' orbits
	(alert "\nInput radii of two planets")
	(setq ref_orb (getreal "\nradius of reference planet(def=149.60)")
		cmp_orb (getreal "\nradius of comparison planet(def=108.21)")
	)
	(if (= ref_orb nil) (setq ref_orb 149.60))
	(if (= cmp_orb nil) (setq cmp_orb 108.21))

;;(Earth) Days of Tropical years of two planets
	(alert "\nInput (earth) days of one tropical year for each planet")
	(setq ref_day (getreal "\nHow many days in one rotation of reference planet(def=365.242)")
		cmp_day (getreal "\nHow many days in one rotation of comparison planet(def=224.695)")
	)
	(if (= ref_day nil) (setq ref_day 365.242))
	(if (= cmp_day nil) (setq cmp_day 224.695))
;;Input one step in earth's day
	(setq e_day (getreal "\none step in earth's day(def=3 )"))
	(if (= e_day nil) (setq e_day 3.))
	(setq 	pnt_s '(0 0)
		ratio (/ ref_day cmp_day)
		step_deg (* e_day (/ 360. ref_day ))
		pnt_ref (list ref_orb 0.)
		pnt_cmp (list cmp_orb 0.)
		
		sum_orb (+ ref_orb cmp_orb)
		dif_orb (abs (- ref_orb cmp_orb))
		cmp_pos_old (list (- sum_orb) 0.)
		ref_pos_old (list (- ref_orb) 0.)
		step 1
	)
	(setq n_repeat (getint "\nHow many steps(def = 973)"))
		(if (= n_repeat nil) (setq n_repeat 973))
;;draw orbits
	(make_circle_1 "0" 3 pnt_s ref_orb)
		(setq ref_orbit (entlast))
	(make_circle_1 "0" 2 pnt_s cmp_orb)
		(setq cmp_orbit (entlast))
	(make_line_1 "0" 0 pnt_ref pnt_cmp)
;;draw planets--ref in green, cmp in yellow, and sun in red
	
	(my_block_insert "green_ball" pnt_ref 5.0 )
		(setq ref_pos (entlast))
	(my_block_insert "yellow_ball" pnt_cmp 5.0 )
		(setq cmp_pos (entlast))
	(my_block_insert "red_ball" pnt_s 10.0 )
		(setq s_pos (entlast))
	(if (= ICAD 0) (command "shademode" "G"))
	
	(command "_.zoom" "_E")
	(setq delay_time (getint "\ndelay speed between position change(def= 50 ms)"))
	(if (= delay_time nil) (setq delay_time 50))
)
;;;
;;;
;;;SETUP_planets_b
;;;
(defun setup_planets_b()
	(setup_sysvar)

;;Radii of two planets' orbits
	(alert "\nInput radii of two planets")
	(setq ref_orb (getreal "\nradius of reference planet(def=149.60)")
		cmp_orb (getreal "\nradius of comparison planet(def=108.21)")
	)
	(if (= ref_orb nil) (setq ref_orb 149.60))
	(if (= cmp_orb nil) (setq cmp_orb 108.21))

;;(Earth) Days of Tropical years of two planets
	(alert "\nInput (earth) days of one tropical year for each planet")
	(setq ref_day (getreal "\nHow many days in one rotation of reference planet(def=365.242)")
		cmp_day (getreal "\nHow many days in one rotation of comparison planet(def=224.695)")
	)
	(if (= ref_day nil) (setq ref_day 365.242))
	(if (= cmp_day nil) (setq cmp_day 224.695))
;;Input one step in earth's day
	(setq e_day (getreal "\none step in earth's days(def=3 )"))
	(if (= e_day nil) (setq e_day 3.))
	(setq 	pnt_s '(0 0)
		ratio (/ ref_day cmp_day)
		step_deg (* e_day (/ 360. ref_day ))
		pnt_ref (list ref_orb 0.)
		pnt_cmp (list cmp_orb 0.)
		
		sum_orb (+ ref_orb cmp_orb)
		dif_orb (abs (- ref_orb cmp_orb))
		cmp_pos_old (list (- sum_orb) 0.)
		ref_pos_old (list (- ref_orb) 0.)
		step 1
	)
	(setq n_repeat (getint "\nHow many steps(def = 973)"))
		(if (= n_repeat nil) (setq n_repeat 973))
;;draw orbits
	;;Orbits for Sun(solid), min & max distance from the earth
	(make_circle_1 "0" 8 pnt_s dif_orb)
	(make_circle_1 "0" 0 pnt_s ref_orb)
	(make_circle_1 "0" 8 pnt_s sum_orb)

	
;;draw planets--ref in green, cmp in yellow, and sun in red
	
	(my_block_insert "green_ball" pnt_s 5.0 )
		(setq e_pos (entlast))
	(my_block_insert "yellow_ball" cmp_pos_old 5.0 )
		(setq cmp_pos (entlast))
	(my_block_insert "red_ball" ref_pos_old 10.0 )
		(setq ref_pos (entlast))
	(if (= ICAD 0) (command "shademode" "G"))
	
	(command "_.zoom" "_E")
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 50 ms)"))
	(if (= delay_time nil) (setq delay_time 50))
)
;;;
;;;----------------------------------------------------------------------------------------
;;;
;;;main
;;;
;;;Earth_Venus
;;;
(defun c:earth_venus_1()
	(setup_e_v)
	
	(make_circle_1 "0" 3 pnt_s e_orb)
		(setq e_orbit (entlast))
	(make_circle_1 "0" 2 pnt_s v_orb)
		(setq v_orbit (entlast))
	(make_line_1 "0" 0 pnt_e pnt_v)	
	(my_block_insert "green_ball" pnt_e 5.0 )
		(setq e_pos (entlast))
	(my_block_insert "yellow_ball" pnt_v 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" pnt_s 10.0 )
		(setq s_pos (entlast))
	(command "_.zoom" "_E")
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 50 ms)"))
	(if (= delay_time nil) (setq delay_time 50))

	(repeat n_repeat
		(entdel e_pos)
		(entdel v_pos)
		(setq deg (* step step_deg)
			rad (dtr deg)
			v_rad (* ratio rad)
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
		)
		(make_line_1 "0" 8 pnt_e pnt_v)
		(my_block_insert "yellow_ball" pnt_v 5.0 )
			(setq v_pos (entlast))
		(my_block_insert "green_ball" pnt_e 5.0 )
			(setq e_pos (entlast))
		(setq step (1+ step))
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" delay_time)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;SETUP_E_V
;;;
(defun setup_e_v()
	(setup_sysvar)
	(if (= ICAD 0) (command "shademode" "G"))
	(setq e_orb 149.60 v_orb 108.21
		e_period 365.242191 v_period 224.695
		pnt_s '(0 0)
		ratio (/ e_period v_period)
		v_zero 0. e_zero 0.
		step_deg (* 3. (/ 360. 365.242 ))
		pnt_e '(149.60 0)
		pnt_v '(108.21 0)
		step 1
		sum_orb (+ e_orb v_orb)
		dif_orb (- e_orb v_orb)
		v_pos_old (list (- sum_orb) 0.)
		s_pos_old (list (- e_orb) 0.)
	)
	(setq n_repeat (getint "\nHow many steps(def = 973)"))
		(if (= n_repeat nil) (setq n_repeat 973))
)
;;;
;;;
;;;
(defun c:earth_venus_1_color()
	(setup_e_v)
	
	(make_circle_1 "0" 3 pnt_s e_orb)
		(setq e_orbit (entlast))
	(make_circle_1 "0" 2 pnt_s v_orb)
		(setq v_orbit (entlast))
	(make_line_1 "0" 0 pnt_e pnt_v)	
	(my_block_insert "green_ball" pnt_e 5.0 )
		(setq e_pos (entlast))
	(my_block_insert "yellow_ball" pnt_v 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" pnt_s 10.0 )
		(setq s_pos (entlast))
	(command "_.zoom" "_E")
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 50 ms)"))
	(if (= delay_time nil) (setq delay_time 50))
	(repeat n_repeat
		(entdel e_pos)
		(entdel v_pos)
		(setq col_id   (1+ (fix (/ step 195))) )
		;(setq col_id (rem step 8))
		(setq deg (* step step_deg)
			rad  (dtr deg)
			;v_rad (+ pi (* ratio rad))
			v_rad (* ratio rad)
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
		)
		(make_line_1 "0" col_id pnt_e pnt_v)
		(my_block_insert "yellow_ball" pnt_v 5.0 )
			(setq v_pos (entlast))
		(my_block_insert "green_ball" pnt_e 5.0 )
			(setq e_pos (entlast))
		(setq step (1+ step))
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" 50)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;-----------------------------------------------------------------------------------------------------
;;;
;;;
(defun c:earth_venus_2()
	(setup_e_v)

;;Orbits for Sun(solid), min & max distance from the earth
	(make_circle_1 "0" 8 pnt_s dif_orb)
	(make_circle_1 "0" 0 pnt_s e_orb)
	(make_circle_1 "0" 8 pnt_s sum_orb)

;;identify the position of Earth(green),Venus(yellow) & Sun(red)		
	(my_block_insert "green_ball" pnt_s 5.0 )
		(setq e_pos (entlast))
	(my_block_insert "yellow_ball" v_pos_old 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" s_pos_old 10.0 )
		(setq s_pos (entlast))
	(command "_.zoom" "_E")
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 20 ms)"))
	(if (= delay_time nil) (setq delay_time 20))	
	(repeat n_repeat
		(setq deg (* step step_deg)
			rad (dtr deg)
			v_rad (+ pi (* ratio rad))
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
			r_len (distance pnt_e pnt_v)
			theta (angle pnt_e pnt_v)
			v_pos_new (polar pnt_s theta r_len)
			theta_s (angle pnt_e pnt_s)
			s_pos_new (polar pnt_s theta_s e_orb)
		)
		(make_line_1 "0" 8 v_pos_old v_pos_new)
		(setq step (1+ step))
		(setq v_pos_old v_pos_new s_pos_old s_pos_new)
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" 20)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;
(defun c:earth_venus_2_color()
	(setup_e_v)
	

;;Orbits for Sun(solid), min & max distance from the earth
	(make_circle_1 "0" 8 pnt_s dif_orb)
	(make_circle_1 "0" 0 pnt_s e_orb)
	(make_circle_1 "0" 8 pnt_s sum_orb)

;;identify the position of Earth(green),Venus(yellow) & Sun(red)		
	
	(my_block_insert "green_ball" pnt_s 5.0 )
		(setq e_pos (entlast))
	(my_block_insert "yellow_ball" v_pos_old 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" s_pos_old 10.0 )
		(setq s_pos (entlast))
	(command "_.zoom" "_E")	
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 20 ms)"))
	(if (= delay_time nil) (setq delay_time 20))
	(repeat n_repeat
		(setq col_id   (1+ (fix (/ step 195))) )
		(setq deg (* step step_deg)
			rad (dtr deg)
			;v_rad (* ratio rad)
			v_rad (+ pi (* ratio rad))
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
			r_len (distance pnt_e pnt_v)
			theta (angle pnt_e pnt_v)
			v_pos_new (polar pnt_s theta r_len)
			theta_s (angle pnt_e pnt_s)
			s_pos_new (polar pnt_s theta_s e_orb)
		)
		(make_line_1 "0" col_id v_pos_old v_pos_new)
		(setq step (1+ step))
		(setq v_pos_old v_pos_new s_pos_old s_pos_new)
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" 20)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;-------------------------------------------------------------------------------------
;;;
;;;
(defun c:earth_venus_3_a()
	(setup_e_v)

	
;;Orbits for Sun(solid), min & max distance from the earth
	(make_circle_1 "0" 8 pnt_s dif_orb)
	(make_circle_1 "0" 0 pnt_s e_orb)
	(make_circle_1 "0" 8 pnt_s sum_orb)

;;identify the position of Earth(green),Venus(yellow) & Sun(red)		
	;(make_pt "0" 3 pnt_s)
	;(make_pt "0" 2 v_pos_old)
	;(make_pt "0" 1 s_pos_old)
	(my_block_insert "green_ball" pnt_s 5.0 )
		(setq e_pos (entlast))
	(my_block_insert "yellow_ball" v_pos_old 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" s_pos_old 10.0 )
		(setq s_pos (entlast))
	(command "_.zoom" "_E")	
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 20 ms)"))
	(if (= delay_time nil) (setq delay_time 20))
	(repeat n_repeat
		(entdel v_pos)
		(entdel s_pos)
		(setq col_id   (1+ (fix (/ step 195))) )
		(setq deg (* step step_deg)
			rad (dtr deg)
			;v_rad (* ratio rad)
			v_rad (+ pi (* ratio rad))
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
			r_len (distance pnt_e pnt_v)
			theta (angle pnt_e pnt_v)
			v_pos_new (polar pnt_s theta r_len)
			theta_s (angle pnt_e pnt_s)
			s_pos_new (polar pnt_s theta_s e_orb)
		)
		(make_line_1 "0" col_id v_pos_old v_pos_new)
		(my_block_insert "yellow_ball" v_pos_old 5.0 )
			(setq v_pos (entlast))
		(my_block_insert "red_ball" s_pos_old 10.0 )
			(setq s_pos (entlast))
		(setq step (1+ step))
		(setq v_pos_old v_pos_new s_pos_old s_pos_new)
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" 20)
	)
;;;end of loop
	(reset_sysvar)
)
;;;

;;;
;;;
;;;
(defun c:earth_venus_3_c()
	(setup_e_v)

;;Orbits for Sun(solid), min & max distance from the earth
	(make_circle_1 "0" 8 pnt_s dif_orb)
	(make_circle_1 "0" 0 pnt_s e_orb)
	(make_circle_1 "0" 8 pnt_s sum_orb)

;;identify the position of Earth(green),Venus(yellow) & Sun(red)		
	(my_block_insert "green_ball" pnt_s 5.0 )
	(my_block_insert "yellow_ball" v_pos_old 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" s_pos_old 10.0 )
		(setq s_pos (entlast))
	(command "_.vpoint" '(0 -1 -0.1))
	(command "_.zoom" "_c" pnt_s 510)
	
	(command "_.delay" 500)	
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 50 ms)"))
	(if (= delay_time nil) (setq delay_time 50))	
	(repeat n_repeat
		(entdel v_pos)
		(entdel s_pos)
		(setq col_id   (1+ (fix (/ step 195))) )
		(setq deg (* step step_deg)
			rad (dtr deg)
			;v_rad (* ratio rad)
			v_rad (+ pi (* ratio rad))
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
			r_len (distance pnt_e pnt_v)
			theta (angle pnt_e pnt_v)
			v_pos_new (polar pnt_s theta r_len)
			theta_s (angle pnt_e pnt_s)
			s_pos_new (polar pnt_s theta_s e_orb)
		)
		
		(my_block_insert "yellow_ball" v_pos_new 5.0 )
			(setq v_pos (entlast))
		(my_block_insert "red_ball" s_pos_new 10.0 )
			(setq s_pos (entlast))
		;(make_line_1 "0" col_id v_pos_new s_pos_new)
		(setq step (1+ step))
		(setq v_pos_old v_pos_new s_pos_old s_pos_new)
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" delay_time)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;
;;;
;;;
(defun c:earth_venus_3_b()
	(setup_e_v)

;;Orbits for Sun(solid), min & max distance from the earth
	(make_circle_1 "0" 8 pnt_s dif_orb)
	(make_circle_1 "0" 0 pnt_s e_orb)
	(make_circle_1 "0" 8 pnt_s sum_orb)

;;identify the position of Earth(green),Venus(yellow) & Sun(red)		
	(my_block_insert "green_ball" pnt_s 5.0 )
	(my_block_insert "yellow_ball" v_pos_old 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" s_pos_old 10.0 )
		(setq s_pos (entlast))
	;(command "_.vpoint" '(0 -1 -0.1))
	(command "_.zoom" "_c" pnt_s 510)
	
	(command "_.delay" 500)	
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 50 ms)"))
	(if (= delay_time nil) (setq delay_time 50))	
	(repeat n_repeat
		(entdel v_pos)
		(entdel s_pos)
		(setq col_id   (1+ (fix (/ step 195))) )
		(setq deg (* step step_deg)
			rad (dtr deg)
			;v_rad (* ratio rad)
			v_rad (+ pi (* ratio rad))
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
			r_len (distance pnt_e pnt_v)
			theta (angle pnt_e pnt_v)
			v_pos_new (polar pnt_s theta r_len)
			theta_s (angle pnt_e pnt_s)
			s_pos_new (polar pnt_s theta_s e_orb)
		)
		
		(my_block_insert "yellow_ball" v_pos_new 5.0 )
			(setq v_pos (entlast))
		(my_block_insert "red_ball" s_pos_new 10.0 )
			(setq s_pos (entlast))
		(make_line_1 "0" col_id v_pos_new s_pos_new)
		(setq step (1+ step))
		(setq v_pos_old v_pos_new s_pos_old s_pos_new)
		(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" delay_time)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;
;;;
;;;
(defun c:earth_venus_3_d()
	(setup_e_v)

;;Orbits for Sun(solid), min & max distance from the earth
	(make_circle_1 "0" 8 pnt_s dif_orb)
	(make_circle_1 "0" 0 pnt_s e_orb)
	(make_circle_1 "0" 8 pnt_s sum_orb)

;;identify the position of Earth(green),Venus(yellow) & Sun(red)		
	(my_block_insert "green_ball" pnt_s 5.0 )
	(my_block_insert "yellow_ball" v_pos_old 5.0 )
		(setq v_pos (entlast))
	(my_block_insert "red_ball" s_pos_old 10.0 )
		(setq s_pos (entlast))
	(command "_.vpoint" '(238. -921. -175.))
	(command "_.zoom" "_c" pnt_s 510)
	
	(command "_.delay" 500)	
	(make_jpg)
	(setq delay_time (getint "\ndelay speed between position change(def= 50 ms)"))
	(if (= delay_time nil) (setq delay_time 50))	
	(repeat n_repeat
		(entdel v_pos)
		(entdel s_pos)
		(setq col_id   (1+ (fix (/ step 195))) )
		(setq deg (* step step_deg)
			rad (dtr deg)
			;v_rad (* ratio rad)
			v_rad (+ pi (* ratio rad))
			pnt_e (list (* e_orb (cos rad)) (* e_orb (sin rad)))
			pnt_v (list (* v_orb (cos v_rad)) (* v_orb (sin v_rad)))
			r_len (distance pnt_e pnt_v)
			theta (angle pnt_e pnt_v)
			v_pos_new (polar pnt_s theta r_len)
			theta_s (angle pnt_e pnt_s)
			s_pos_new (polar pnt_s theta_s e_orb)
		)
		
		(my_block_insert "yellow_ball" v_pos_new 5.0 )
			(setq v_pos (entlast))
		(my_block_insert "red_ball" s_pos_new 10.0 )
			(setq s_pos (entlast))
		(make_line_1 "0" col_id v_pos_new v_pos_old)
		(setq step (1+ step))
		(setq v_pos_old v_pos_new s_pos_old s_pos_new)
		(if (= (rem step 2) 0) (make_jpg))
	(command "_.delay" delay_time)
	)
;;;end of loop
	(reset_sysvar)
)
;;;
;;;
;;;------------------------------------------------------------------------------------
;;;
;;;DRAW_EPI_CYCLOID
;;;
;;;	x=(a+b)cos(t)-b cos{(a+b)t/b}
;;;	y=(a+b)sin(t)-b sin{(a+b)t/b}
;;;		where a :inner radius
;;;		      b :outer radius
;;;		      t :angle 
;;;
(defun c:draw_epi_cycloid()
	(setup_epi_cycloid)
	(make_jpg)
	(command "_.delay" 500)
;;repeat loop
	(repeat n_repeat
		(setq theta (dtr (* step inc_deg))
			theta_1  (* sum_by_out theta)
			x (- (* rad_sum (cos theta)) (* rad_out (cos theta_1)))
			y (- (* rad_sum (sin theta)) (* rad_out (sin theta_1)))
			new_pos (list x y)
		)
		;(make_pt "0" 0 new_pos)
		(make_line_1 "0" 8 old_pos new_pos)
		(setq step (1+ step) 
			old_pos new_pos
		)
	(if (= (rem step 10) 0) (make_jpg))
	(command "_.delay" 10)
	)
;;end of repeat loop

	(reset_sysvar)
)
;;;
;;;SETUP_EPI_CYCLOID
;;;
(defun setup_epi_cycloid()
;;Input inner & outer circle radii
	(setup_sysvar)
	(alert "\nInput Inner & outer circle radii")
	(setq rad_in (getreal "\nInnner circle radius (def = 1.0)")
		rad_out (getreal "\nOuter circle radius (def = 1.0)")
	)
	(if (= rad_in nil) (setq rad_in 1.0))
	(if (= rad_out nil) (setq rad_out 1.0))
	(setq ctr_in '(0 0)
		rad_sum (+ rad_in rad_out)
		ctr_out (list rad_sum 0)
		ref_len (* 1.01 (+ rad_in (* 2. rad_out)))
		up_right (list ref_len ref_len)
		low_left (list (- ref_len) (- ref_len))
	)

;;draw two reference circles
	(make_circle_1 "0" 8 ctr_in  rad_in)
	(make_circle_1 "0" 8 ctr_out rad_out)
	(command "_.zoom" "_w" low_left up_right)

;;Input range of angle from zero deg to 
	(alert "\nMaximum angle (in deg)")
	(setq max_ang (getreal "\nMaximum angle (deg) (def = 360.)"))
	(if (= max_ang nil) (setq max_ang 360.))
;;Input angle increment (def = 1 deg)
	(alert "\nInput angle increment(deg) (def = 1.0)")
	(setq inc_deg (getreal "\nAngle increment (def=1.0)"))
	(if (= inc_deg nil) (setq inc_deg 1.))
;;
	(setq step 0 
		sum_by_out (/ rad_sum rad_out)
		n_repeat (fix (/ max_ang inc_deg))
		old_pos (list rad_in 0) 
	)
)
;;;
;;;