def move_forward(self, distance, smooth = 1.0, straight = True):
"""Move worm peristaltically forward
Arguments:
distance (number): distance to move forward
smooth (number): smoothness of the interpolation
straight (bool): if True extrapolated points move straight
Note:
The head is first point in center line and postive distances will move the
worm in this direction.
"""
length = self.length;
cline = self.center_line();
cinterp, u = splprep(cline.T, u = None, s = smooth, per = 0)
us = u - distance / length;
x, y = splev(us, cinterp, der = 0);
cline2 = np.array([x,y]).T;
if straight:
if distance > 0:
idx = np.nonzero(us < 0)[0];
if len(idx) > 0:
d = cline[0,:] - cline[1,:];
#l = np.linalg.norm(d);
l = self.length / (self.npoints -1);
d = d / l;
m = idx.max();
for i in idx:
cline2[i,:] = cline[0,:] + distance * d * (m + 1.0 - i)/(m + 1.0);
elif distance < 0:
idx = np.nonzero(us > 1)[0];
if len(idx) > 0:
d = cline[-1,:] - cline[-2,:];
#l = np.linalg.norm(d);
l = self.length / (self.npoints -1);
d = d / l;
m = idx.min(); mx = idx.max();
for i in idx:
cline2[i,:] = cline[-1,:] - distance * d * (i - m + 1.0)/(mx + 1.0 - m);
self.from_center_line(cline2, self.width);
self.stretch(length / self.length);
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