# PyCannon.py
# A Physics Simulation

from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
from numpy import *
import sys

global velhoriz
global velvert

def init():
	global velhoriz
	global velvert
	
	# White background
	glClearColor(1.0, 1.0, 1.0, 1.0)
	
	# Large range for long shots
	gluOrtho2D(-200.0, 12000.0, -200.0, 5000.0)

	# Input angle and muzzle velocity
	angle = input("Enter the angle of elevation: ")
	muzzvel = input("Enter the muzzle velocity of the shell: ")
	
	# Convert the degree angle to radians
	radangle = (angle*3.1415926)/180
	
	# Solve for horizontal and vertical initial velocities
	velhoriz = muzzvel*cos(radangle)
	velvert = muzzvel*sin(radangle)
	
	# Print out the initial velocities in the console
	print
	print ("Horizontal Velocity (m/s) = "), velhoriz
	print ("Vertical Velocity (m/s) = "), velvert
	
def plottrajectory():
	global velvert
	global velhoriz

	# We can now calculate and change vvel
	# While preserving the original velVert
	vvel = velvert
	hvel = velhoriz	

	glClear(GL_COLOR_BUFFER_BIT)
	glColor3f(0.0, 0.0, 0.0)
	
	# Draw some horizontal and vertical axis lines
	glLineWidth(2.0)
	glBegin(GL_LINES)
	glVertex2f(0.0, 0.0)
	glVertex2f(20000.0, 0.0)
	glVertex2f(0.0, 0.0)
	glVertex2f(0.0, 15000.0)
	glEnd()
	
	# Set the height of the cannon barrel
	# Initalize variables for later use
	height = 2.0
	dtime = 0.0001
	dist = 0.0
	maxheight = 0.0
	totaltime = 0.0
	
	# Plot the trajectory as long
	# as the height is above the ground
	while height > 0.0:
			
			# Equations to calculate distance and
			# Height for each unit of time.
			dist = dist + hvel*dtime
			vvel = vvel - 9.8*dtime
			height = height + vvel*dtime
			totaltime += dtime
			
			# Find the max height.
			if maxheight < height:
				maxheight = height
			
			# Plot the trajectory
			glBegin(GL_POINTS)
			glVertex2f(dist, height)
			glEnd()
	glFlush()
		
	# Print the solutions.  Not indented!
	print
	print("Distance traveled (m) = "), dist
	print("Maximum altitude (m) = "), maxheight
	print("Total Time = "), totaltime
						
def main():
	glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE)
	glutInitWindowPosition(50, 50)
	glutInitWindowSize(800, 600)
	glutInit(sys.argv)
	glutCreateWindow("How Far Will It Go?")
	glutDisplayFunc(plottrajectory)
	init()
	glutMainLoop()
	
main()	

# End Program