spiderweb.py

"""Showcase of a elastic spiderweb (drawing with pyglet)

It is possible to grab one of the crossings with the mouse
"""

__version__ = "$Id:$"
__docformat__ = "reStructuredText"

import math, random

import pyglet
    
import pymunk
from pymunk.vec2d import Vec2d

config = pyglet.gl.Config(sample_buffers=1, samples=2, double_buffer=True)
window = pyglet.window.Window(config=config, vsync = False)
space = pymunk.Space()

space.gravity = 0,-900
space.damping = .999
c = Vec2d(window.width /2., window.height / 2.)        
        
### WEB
web_group = 1
bs = []
dist = .3

cb = pymunk.Body(1,1)
cb.position = c
s = pymunk.Circle(cb, 15) # to have something to grab
s.filter = pymunk.ShapeFilter(group = web_group)
s.ignore_draw = True
space.add(cb, s)


#generate each crossing in the net
for x in range(0,101):
    b = pymunk.Body(1, 1)
    v = Vec2d.unit()
    v.angle_degrees = x*18
    scale = window.height / 2. / 6. * .5
    
    dist += 1/18. 
    dist = dist ** 1.005
    
    offset = 0
    offset = [0.0, -0.80, -1.0, -0.80][((x*18) % 360)//18 % 4]
    offset = .8 + offset
    
    offset *= dist**2.8 / 100.
    
    #print "offset", offset
    
    v.length = scale * (dist + offset) 
    
    b.position = c + v
    s = pymunk.Circle(b, 15)
    s.filter = pymunk.ShapeFilter(group = web_group)
    s.ignore_draw = True
    space.add(b,s)
    bs.append(b)
    
def add_joint(a,b):
    rl = a.position.get_distance(b.position) * 0.9
    stiffness = 5000.
    damping = 100
    j = pymunk.DampedSpring(a, b, (0,0), (0,0), rl, stiffness, damping)
    j.max_bias = 1000
    #j.max_force = 50000
    space.add(j)
    
for b in bs[:20]:
    add_joint(cb,b)
    
for i in range(len(bs)-1):
    add_joint(bs[i], bs[i+1])

    i2 = i+20
    if len(bs) > i2:
        add_joint(bs[i], bs[i2])   

        
### WEB ATTACH POINTS
static_bs = []
for b in bs[-17::4]:
    static_body = pymunk.Body(body_type = pymunk.Body.STATIC)
    static_body.position = b.position
    static_bs.append(static_body)
    
    j = pymunk.PivotJoint(static_body, b, static_body.position)
    j = pymunk.DampedSpring(static_body, b, (0,0), (0,0), 0, 0, 0)
    j.damping = 100
    j.stiffness = 20000
    space.add(j)

### ALL SETUP DONE 
    
def update(dt):
    # Note that we dont use dt as input into step. That is because the 
    # simulation will behave much better if the step size doesnt change 
    # between frames.
    r = 10
    for x in range(r):
        space.step(1./30./r)                

pyglet.clock.schedule_interval(update, 1/30.)

selected = None
selected_joint = None
mouse_body = pymunk.Body(body_type = pymunk.Body.KINEMATIC)

@window.event
def on_mouse_press(x, y, button, modifiers):
    mouse_body.position = x,y
    hit = space.point_query_nearest((x,y), 10, pymunk.ShapeFilter())
    if hit != None:
        global selected
        body = hit.shape.body
        rest_length = mouse_body.position.get_distance(body.position)
        stiffness = 1000
        damping = 10
        selected = pymunk.DampedSpring(mouse_body, body, (0,0), (0,0), rest_length, stiffness, damping)
        space.add(selected)
        
@window.event
def on_mouse_release(x, y, button, modifiers):
    global selected
    if selected != None:
        space.remove(selected)
        selected = None
    
@window.event
def on_mouse_drag(x, y, dx, dy, buttons, modifiers):
    mouse_body.position = x,y
   
@window.event
def on_key_press(symbol, modifiers):
    if symbol == pyglet.window.key.P:
        pyglet.image.get_buffer_manager().get_color_buffer().save('spiderweb.png')

   
fps_display = pyglet.clock.ClockDisplay()

@window.event
def on_draw():
    pyglet.gl.glClearColor(240,240,240,255)
    window.clear()
    
    fps_display.draw()
    
    # static attach points
    pyglet.gl.glColor3f(1,0,1)
    pyglet.gl.glPointSize(6)
    a = []
    for b in static_bs:
        a += [b.position.x, b.position.y]
        pyglet.graphics.draw(len(a)//2, pyglet.gl.GL_POINTS, ('v2f',a))
    
    # web crossings / bodies
    pyglet.gl.glColor3f(.8,.8,.8)
    a = []
    for b in bs:
        a += [b.position.x, b.position.y]
    pyglet.gl.glPointSize(4)
    pyglet.graphics.draw(len(a)//2, pyglet.gl.GL_POINTS, ('v2f',a))
    
    
    # web net / constraints
    a = []
    for j in space.constraints:
        a += [j.a.position.x, j.a.position.y, j.b.position.x, j.b.position.y]
        pass
    
    pyglet.graphics.draw(len(a)//2, pyglet.gl.GL_LINES, ('v2f',a))
     
    # anything else
    
pyglet.app.run()