pendulum_art.py

from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *
import time
import math

B = 6000    
L = 3000
H = 400
g = 1000.0
k = 0.005
theta = 50.0*math.pi/180.0
phi = 0.0
v_phi = 180.0
v_theta = -0.0001
theta_d = v_theta / L
phi_d = v_phi / (L*math.sin(theta))
C0 = math.sin(theta)*math.sin(theta)*phi_d

t0 = time.time()
tr = time.time() - t0
t = 0.0

def polar_to_xy():
    rho = float(L)*math.sin(theta)
    return float(B)/2.0 - rho*math.cos(phi), float(B)/2.0 - rho*math.sin(phi)

last_x, last_y = polar_to_xy()

L_SCALE = 1.0/100.0

def square():
    global t,theta,phi,theta_d,phi_d,last_x,last_y,tr
    # Time keeping
    t_new = time.time() - t0
    dt = (t_new - tr)*6
    tr = t_new
    t = t + dt
    # Physics
    theta += theta_d * dt
    phi += phi_d * dt 
    phi_d = C0*math.exp(-t*k) / (math.sin(theta)*math.sin(theta)+0.0000001)
    # print(f"{theta_d}|{phi_d}")
    theta_dd = -k*theta_d - g*(1.0/float(L))*math.sin(theta) + (phi_d*phi_d*math.sin(theta)*math.cos(theta))
    # theta_dd = - g*(1.0/float(L))*math.sin(theta) + (phi_d*phi_d*math.sin(theta)*math.cos(theta))

    theta_d += theta_dd*dt
    # Drawing
    x_new, y_new = polar_to_xy()
    glBegin(GL_LINE_STRIP)
    glVertex2f(last_x, last_y)
    glVertex2f(x_new,y_new)
    glEnd()
    last_x,last_y = x_new,y_new


def iterate():
    glViewport(0, 0, 1000, 1000)
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    glOrtho(0.0, B, 0.0, B, 0.0, 1.0)
    glMatrixMode (GL_MODELVIEW)
    glLoadIdentity()

def showScreen():
    # glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glLoadIdentity()
    iterate()
    glColor3f(1.0, 0.0, 3.0)
    square()
    glutSwapBuffers()

glutInit()
glutInitDisplayMode(GLUT_RGBA)
glutInitWindowSize(1000, 1000)
glutInitWindowPosition(0, 0)
wind = glutCreateWindow("OpenGL Coding Practice")
glutDisplayFunc(showScreen)
glutIdleFunc(showScreen)
glutMainLoop()