## Model 2:  Graphs of Motion

from __future__ import division
from visual import *
from visual.graph import * ## invoke graphing routines
scene.x=512
#scene.y = 600
scene.width =800
scene.height = 380



## User input to get program parameters
#### Get values for the initial velocity and force
x0 = vector(input("Enter the initial position:"))
x0.y=0 #Motion in 1-D for now!
x0.z=0
print "Initial position =", x0

v0 = vector(input("Enter the initial x-dir velocity:"))
v0.y=0 #Motion in 1-D for now!
v0.z=0
print "Initial velocity =", v0

a = vector(input("Enter the x-dir acceleration:"))
a.y=0  #Motion in 1-D for now!
a.z=0
print "Acceleration =", a

#### Define the initial time and time step size
##deltat = input("Enter the time step size:")
##t = 0

deltat=0.01
t=0

## OBJECTS AND INITIAL VALUES
track = box(pos=vector(0,-.35,0),
            size=(4.0,.05,.10), color=color.white)
y_offset = track.pos.y + track.size.y/2
track_x_offset = track.size.x/2   #Make x=0, the left edge of the track
x0.x=x0.x-track_x_offset
x0.y=x0.y+y_offset
cart = box(pos=x0,size=(.1,.04,.06), color=color.green)
cart.m = 1

#incline = box(pos=vector(0,-.35,0), axis=(1,1,0),
          #  size=(4.0,.05,.10), color=color.white)

## Define initial cart momentum using mass and velocity
cart.p = cart.m*v0
print 'initial cart momentum =', cart.p

## create object that draws a trail behind cart
trail = curve(color=cart.color)


## SET UP GRAPHS
## x-motion graphs
XMothionWindow = gdisplay(title='x-dir displacement, velocity and acceleration',
        xtitle='t', ytitle='x(m) - yellow, v_x(m/s) - red, a_x(m/s^2) - cyan',
        width=512, height=200)
x_graph = gcurve(color=color.yellow) ## create a gcurve for x displacement
dx_initialize = gdots(color=color.black) #Plot a dot to cut down on autoscaling
dx_initialize.plot(pos=(.5, .5))

## create a gcurve for x velocity
XVelWindow = gdisplay(x=0, y=201, title='x-dir velocity',xtitle='t',
        ytitle='vx(m/s)',
        width=512, height=200)
vx_graph = gcurve(color=color.red)
vx_initialize = gdots(color=color.black) #Plot a dot to cut down on autoscaling
vx_initialize.plot(pos=(.5, .5))

# create a gcurve for x acceleration
XAccWindow = gdisplay(x=0, y=401, title='y-dir accel',xtitle='t',
        ytitle='ax(m/s^2)',
        width=512, height=200)
ax_graph = gcurve(color=color.cyan)
ax_initialize = gdots(color=color.black) #Plot a dot to cut down on autoscaling
ax_initialize.plot(pos=(.5, .5))


g=9.8
## CALCULATIONS
while -2.1< cart.pos.x <= 2 and t<2:
    #print 'the time is now', t
    #Ffan = vector(-10,0,0)
    Fair = -mag(cart.p/cart.m)*cart.p/cart.m
    Fgrav = cart.m*vector(0,-g,0) 
    Fnet = a*cart.m
    ## momentum update
    cart.p = cart.p + Fnet*deltat
    ## position update
    cart.pos = cart.pos + (cart.p/cart.m)*deltat
    if cart.pos.y<-.3:
        cart.pos.y=-.3
        cart.p.y=0
        
        
    ## update trail
    trail.append(pos=cart.pos)

    ## x-dir plots
    x_graph.plot(pos=(t,cart.pos.x + track_x_offset)) ## add a point to the x-position graph
    vx_graph.plot(pos=(t,cart.p.x/cart.m)) ## add a point to the x-dir velocity graph
    ax_graph.plot(pos=(t,Fnet.x/cart.m)) ## add a point to the x-dir acceleration graph

    ## advance time
    t = t + deltat
    
    rate(20)
print 'After the loop. The final time is', t