#copyright (c) Aaron Titus, 2004
#licensed under the gpl license

#http://linus.highpoint.edu/~atitus/mandi/vpython

from visual import *
from __future__ import division

print "Simulation of a rotating, translating ring."
print ""
print "Click to begin, click to stop, click to go to the next sequence."

#Note that sequences are defined in the animate() function
	
#0 do not show planet
#1 show planet
showPlanet=0

#0 do not show points
#1 show points
showPoints=0

#0 do not show ring
#1 show ring
showRing=1

R=1 #radius

scene.autoscale=0
scene.range=3.2*R

scene.height=400
scene.width=800

#define how many points around the ring by specifiying their angular separation
dtheta = 45/180*pi
theta0=0

#colors
pointColor=color.red
rotArrowColor=color.yellow
transArrowColor=color.blue
vArrowColor=color.green

#lists of points and vectors
points=[]
vRotVectors=[]
vTransVectors=[]
vVectors=[]

rTrans0=vector(-2,0,0) #initial position of the planet
rTrans=rTrans0

vTrans0=vector(2,0,0) #initial velocity of the planet
vTrans=vTrans0

omega0=1 #initial angular velocity
omega=omega0
omegaHat=omega/abs(omega)

t=0
dt=0.002

arrowScale=0.5

planet=sphere(radius=R, color=pointColor, pos=rTrans)
planet.visible=showPlanet

circum=ring(radius=R, color=pointColor, axis=(0,0,1), pos=rTrans,thickness=0.01*R)
circum.visible=showRing

#create points and arrows
for theta in arange(theta0,2*pi,dtheta):
	pointPos=rTrans+vector(R*cos(theta),R*sin(theta),0)
	thisPoint=sphere(radius=0.05*R, pos=pointPos, color=pointColor)
	points.append(thisPoint)
	vRotVectors.append(arrow(color=rotArrowColor,pos=pointPos,axis=(0,0,0)))
	vTransVectors.append(arrow(color=transArrowColor,pos=pointPos,axis=(0,0,0)))
	vVectors.append(arrow(color=vArrowColor,pos=pointPos,axis=(0,0,0)))
	if showPoints==0:
		thisPoint.visible=0


def animate(seq):
	global rTrans, vTrans, omega

	#instructions sequence
	#0 custom
	#1 show translation, no rotation
	#2 show rotation, no translation
	#3 show translation and rotation
	#4 show resultant for all points, translation and rotation
	#seq=4
	
	#0 no vectors
	#1 1 rot vector only
	#2 1 trans vector only
	#3 1 of each vector and resultant
	#4 all rot vectors only
	#5 all trans vectors only
	#6 all vectors
	#7 1 resultant
	#8 all resultants
	show=0
	
	#0 do not show tip-to-tail
	#1 show tip-to-tail
	showTipToTail=1
	
	if show==5 or show==1:
		showTipToTail=0 #otherwise, it looks funny

	#set variables for instructional sequence
	if seq==1:
		vTrans=vTrans0
		omega=0
		show=5
		showTipToTail=0
	
	if seq==2:
		vTrans=vector(0,0,0)
		omega=omega0
		show=4
		
	if seq==3:
		vTrans=vTrans0
		omega=omega0
		show=3
		
	if seq==4:
		vTrans=vTrans0
		omega=omega0
		show=8
			
	while 1:
		rate(100)
		dphi=omega*dt
		drTrans=vTrans*dt
	
		for i in range(len(points)):
			point=points[i]
			#find position relative to center
			rRot=point.pos-rTrans
			#rotate ring
			rRot=rotate(rRot,angle=dphi)
			#find new positive relative to origin
			point.pos=rTrans+drTrans+rRot		
			
			#determine arrows
			vRotVectors[i].pos=point.pos
			vRotVectors[i].axis=rotate(rRot,angle=pi/2*omegaHat)*mag(rRot)*R*abs(omega)*arrowScale
			vTransVectors[i].pos=point.pos
			vTransVectors[i].axis=vTrans*arrowScale
			vVectors[i].pos=point.pos
			vVectors[i].axis=vTransVectors[i].axis+vRotVectors[i].axis
			#make arrows invisible by default
			vRotVectors[i].visible=0
			vTransVectors[i].visible=0
			vVectors[i].visible=0
			
			if showTipToTail==1:
				vTransVectors[i].pos=vRotVectors[i].pos+vRotVectors[i].axis
			
			if i==0:
				if show==1 or show==3 or show==4 or show==6:
					vRotVectors[i].visible=1
				if show==2 or show==3 or show==5 or show==6:
					vTransVectors[i].visible=1
				if show==3 or show==6 or show==7 or show==8:
					vVectors[i].visible=1
					
			
			else:
				if show==4 or show == 6:
					vRotVectors[i].visible=1
				if show==5 or show ==6:
					vTransVectors[i].visible=1
				if show==6 or show==8:
					vVectors[i].visible=1
			
		rTrans=rTrans+drTrans	
		planet.pos=rTrans
		circum.pos=rTrans
		
		if scene.mouse.events:
			m=scene.mouse.getevent()
			
			if m.click:
				break
				
def reset():
	global rTrans
	rTrans=rTrans0
	planet.pos=rTrans
	circum.pos=rTrans
	for i in range(len(points)):
		theta=i*dtheta
		points[i].pos=rTrans+vector(R*cos(theta),R*sin(theta),0)
			
iSeq=0 #sequence number
while 1:
	if iSeq==4:
		iSeq=1
	else:
		iSeq=iSeq+1
	scene.mouse.getclick()
	reset() #resets positions of everything
	animate(iSeq)