core/restrain_in_sphere.py

## \example core/restrain_in_sphere.py
# This fragment shows how to restrain a set of points stored in a
# SingletonContainer in a sphere of radius 'radius' centered around
# 'center'.

import IMP
import IMP.core
radius = 10
stiffness = 2
center = IMP.algebra.Vector3D(1, 2, 3)
m = IMP.kernel.Model()
p = m.add_particle("particle")
IMP.core.XYZR.setup_particle(
    m, p, IMP.algebra.Sphere3D(IMP.algebra.Vector3D(100, 0, 0), 1))

ub = IMP.core.HarmonicUpperBound(radius, stiffness)

# Restrain based on the distance to a single point (hence a ball
ss = IMP.core.DistanceToSingletonScore(ub, center)

r = IMP.core.SingletonRestraint(ss, m.get_particle(p))
r.evaluate(False)