Learning-PyOpenGL/falling_snowflakes.py at master · juantresde/Learning-PyOpenGL · GitHub

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from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *
import math
from random import randint

width, height = 400, 400                                # width and height of the window
field_width, field_height = 460, 450                    # size of window where snowflakes appear


RECT_DELAY = 0
RECT_DELAY1 = 20
dx = 0.07
dy = - 0.8
snowflakes = []


def refresh2d(width, height):
    glViewport(0, 0, width, height)
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    glOrtho(0.0, width, 0.0, height, 0.0, 1.0)
    glMatrixMode (GL_MODELVIEW)
    glLoadIdentity()


def draw_circle(cx, cy, r, num_segments):                # drawing the circle
    theta = 2 * math.pi / num_segments
    c = math.cos (theta)
    s = math.sin(theta)
    t = 0.0

    x = r
    y = 0

    glBegin(GL_POLYGON)
    for i in range(0, num_segments):
        glVertex2f(x + cx, y + cy)

        t = x
        x = c * x - s * y
        y = s * t + c * y

    glEnd()


def snow_random(value):                                 # generation of snowflakes
    r = randint(0,50)
    if r == 0:
        x, y = randint(-30, field_width), randint(420, field_height)
        snowflakes.append({"X":x,"Y": y})

    glutTimerFunc(RECT_DELAY, snow_random, 0)


def draw_snowflakes():                                  # drawing snowflakes
    glColor3f(1.0, 1.0, 1.0)
    for i in snowflakes:
        draw_circle(i["X"],i["Y"], 0.9, 40)


def falling_of_snowflakes(value):                       # falling and disappearing
    for i in snowflakes:
        i["X"] += dx
        i["Y"] += dy

        if i["Y"] <= 0 :
            snowflakes.remove(i)
    glutTimerFunc(RECT_DELAY1, falling_of_snowflakes, 0)


def draw():                                             # ondraw is called all the time
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)  # clear the screen
    glLoadIdentity()                                    # reset position

    # ToDo draw rectangle
    refresh2d(width, height)
    draw_snowflakes()

    glutSwapBuffers()                                   # important for double buffering


# initialization
glutInit()                                              # initialize glut
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH)
glutInitWindowSize(width, height)                       # set window size
glutInitWindowPosition(0, 0)                            # set window position
window = glutCreateWindow("Falling snowflakes")         # create window with title
glutDisplayFunc(draw)                                   # set draw function callback
glutIdleFunc(draw)                                      # draw all the time
glutTimerFunc(RECT_DELAY, snow_random, 0)
glutTimerFunc(RECT_DELAY1, falling_of_snowflakes, 0)
glutMainLoop()