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"""Fit circles analytically to measure
the signed curvature of a line"""
from vedo import *
shape = Spline([
[1.0, 2.0, -1.0],
[1.5, 0.0, 0.4],
[2.0, 4.0, 0.5],
[4.0, 1.5, -0.3]],
res=200,
)
n = 5 # nr. of points to use for the fit
npt = shape.npoints
points = shape.points
fitpts, circles, curvs = [], [], [0]*npt
for i in range(n, npt - n-1):
pts = points[i-n:i+n]
center, R, normal = fit_circle(pts)
z = cross(pts[-1]-pts[0], center-pts[0])[2]
curvs[i] = sqrt(1/R) * z/abs(z)
if R < 0.75:
circle = Circle(center, r=R).wireframe()
circle.reorient([0,0,1], normal)
circles.append(circle)
fitpts.append(center)
shape.lw(8).cmap('coolwarm', curvs).add_scalarbar3d(title=':pm1/:sqrtR', c='w')
# use this trick to make the scalarbar3d become a 2d screen object:
shape.scalarbar = shape.scalarbar.clone2d("bottom-right", 0.2)
show(shape, circles, Points(fitpts, c='white'), __doc__, axes=1, bg='bb').close()
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