123 lines
3.0 KiB
Python
123 lines
3.0 KiB
Python
"""
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Mechanical simulation of a chain using verlet integration.
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Use the mouse to interact with one of the chains.
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By default, this uses a slow, pure-python integrator to solve the chain link
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positions. Unix users may compile a small math library to speed this up by
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running the `examples/verlet_chain/make` script.
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"""
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import initExample ## Add path to library (just for examples; you do not need this)
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import pyqtgraph as pg
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from pyqtgraph.Qt import QtCore, QtGui
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import numpy as np
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import verlet_chain
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sim = verlet_chain.ChainSim()
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if verlet_chain.relax.COMPILED:
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# Use more complex chain if compiled mad library is available.
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chlen1 = 80
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chlen2 = 60
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linklen = 1
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else:
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chlen1 = 10
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chlen2 = 8
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linklen = 8
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npts = chlen1 + chlen2
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sim.mass = np.ones(npts)
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sim.mass[int(chlen1 * 0.8)] = 100
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sim.mass[chlen1-1] = 500
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sim.mass[npts-1] = 200
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sim.fixed = np.zeros(npts, dtype=bool)
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sim.fixed[0] = True
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sim.fixed[chlen1] = True
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sim.pos = np.empty((npts, 2))
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sim.pos[:chlen1, 0] = 0
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sim.pos[chlen1:, 0] = 10
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sim.pos[:chlen1, 1] = np.arange(chlen1) * linklen
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sim.pos[chlen1:, 1] = np.arange(chlen2) * linklen
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# to prevent miraculous balancing acts:
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sim.pos += np.random.normal(size=sim.pos.shape, scale=1e-3)
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links1 = [(j, i+j+1) for i in range(chlen1) for j in range(chlen1-i-1)]
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links2 = [(j, i+j+1) for i in range(chlen2) for j in range(chlen2-i-1)]
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sim.links = np.concatenate([np.array(links1), np.array(links2)+chlen1, np.array([[chlen1-1, npts-1]])])
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p1 = sim.pos[sim.links[:,0]]
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p2 = sim.pos[sim.links[:,1]]
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dif = p2-p1
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sim.lengths = (dif**2).sum(axis=1) ** 0.5
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sim.lengths[(chlen1-1):len(links1)] *= 1.05 # let auxiliary links stretch a little
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sim.lengths[(len(links1)+chlen2-1):] *= 1.05
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sim.lengths[-1] = 7
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push1 = np.ones(len(links1), dtype=bool)
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push1[chlen1:] = False
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push2 = np.ones(len(links2), dtype=bool)
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push2[chlen2:] = False
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sim.push = np.concatenate([push1, push2, np.array([True], dtype=bool)])
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sim.pull = np.ones(sim.links.shape[0], dtype=bool)
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sim.pull[-1] = False
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# move chain initially just to generate some motion if the mouse is not over the window
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mousepos = np.array([30, 20])
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def display():
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global view, sim
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view.clear()
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view.addItem(sim.makeGraph())
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def relaxed():
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global app
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display()
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app.processEvents()
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def mouse(pos):
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global mousepos
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pos = view.mapSceneToView(pos)
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mousepos = np.array([pos.x(), pos.y()])
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def update():
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global mousepos
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#sim.pos[0] = sim.pos[0] * 0.9 + mousepos * 0.1
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s = 0.9
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sim.pos[0] = sim.pos[0] * s + mousepos * (1.0-s)
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sim.update()
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app = pg.mkQApp()
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win = pg.GraphicsLayoutWidget()
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win.show()
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view = win.addViewBox()
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view.setAspectLocked(True)
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view.setXRange(-100, 100)
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#view.autoRange()
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view.scene().sigMouseMoved.connect(mouse)
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#display()
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#app.processEvents()
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sim.relaxed.connect(relaxed)
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sim.init()
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sim.relaxed.disconnect(relaxed)
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sim.stepped.connect(display)
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timer = pg.QtCore.QTimer()
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timer.timeout.connect(update)
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timer.start(16)
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if __name__ == '__main__':
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pg.exec()
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