/usr/lib/python2.7/dist-packages/pyqtgraph/examples/verlet_chain/chain.py is in python-pyqtgraph 0.9.10-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 | import pyqtgraph as pg
import numpy as np
import time
from . import relax
class ChainSim(pg.QtCore.QObject):
stepped = pg.QtCore.Signal()
relaxed = pg.QtCore.Signal()
def __init__(self):
pg.QtCore.QObject.__init__(self)
self.damping = 0.1 # 0=full damping, 1=no damping
self.relaxPerStep = 10
self.maxTimeStep = 0.01
self.pos = None # (Npts, 2) float
self.mass = None # (Npts) float
self.fixed = None # (Npts) bool
self.links = None # (Nlinks, 2), uint
self.lengths = None # (Nlinks), float
self.push = None # (Nlinks), bool
self.pull = None # (Nlinks), bool
self.initialized = False
self.lasttime = None
self.lastpos = None
def init(self):
if self.initialized:
return
assert None not in [self.pos, self.mass, self.links, self.lengths]
if self.fixed is None:
self.fixed = np.zeros(self.pos.shape[0], dtype=bool)
if self.push is None:
self.push = np.ones(self.links.shape[0], dtype=bool)
if self.pull is None:
self.pull = np.ones(self.links.shape[0], dtype=bool)
# precompute relative masses across links
l1 = self.links[:,0]
l2 = self.links[:,1]
m1 = self.mass[l1]
m2 = self.mass[l2]
self.mrel1 = (m1 / (m1+m2))[:,np.newaxis]
self.mrel1[self.fixed[l1]] = 1 # fixed point constraint
self.mrel1[self.fixed[l2]] = 0
self.mrel2 = 1.0 - self.mrel1
for i in range(10):
self.relax(n=10)
self.initialized = True
def makeGraph(self):
#g1 = pg.GraphItem(pos=self.pos, adj=self.links[self.rope], pen=0.2, symbol=None)
brushes = np.where(self.fixed, pg.mkBrush(0,0,0,255), pg.mkBrush(50,50,200,255))
g2 = pg.GraphItem(pos=self.pos, adj=self.links[self.push & self.pull], pen=0.5, brush=brushes, symbol='o', size=(self.mass**0.33), pxMode=False)
p = pg.ItemGroup()
#p.addItem(g1)
p.addItem(g2)
return p
def update(self):
# approximate physics with verlet integration
now = pg.ptime.time()
if self.lasttime is None:
dt = 0
else:
dt = now - self.lasttime
self.lasttime = now
# limit amount of work to be done between frames
if not relax.COMPILED:
dt = self.maxTimeStep
if self.lastpos is None:
self.lastpos = self.pos
# remember fixed positions
fixedpos = self.pos[self.fixed]
while dt > 0:
dt1 = min(self.maxTimeStep, dt)
dt -= dt1
# compute motion since last timestep
dx = self.pos - self.lastpos
self.lastpos = self.pos
# update positions for gravity and inertia
acc = np.array([[0, -5]]) * dt1
inertia = dx * (self.damping**(dt1/self.mass))[:,np.newaxis] # with mass-dependent damping
self.pos = self.pos + inertia + acc
self.pos[self.fixed] = fixedpos # fixed point constraint
# correct for link constraints
self.relax(self.relaxPerStep)
self.stepped.emit()
def relax(self, n=50):
# speed up with C magic if possible
relax.relax(self.pos, self.links, self.mrel1, self.mrel2, self.lengths, self.push, self.pull, n)
self.relaxed.emit()
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