markers.py

## \example atom/markers.py
# It is often useful to be able to add extra particles to a model to act as markers for particular features. Examples include creating a bounding sphere for some part of a molecule and using the bounding sphere particle in a distance restraint. The IMP.atom.create_cover() is such a function, creating a particle whose IMP.core.XYZR sphere contains the passed IMP.atom.Selection at all times.
#
# The same code also works (more efficiently in fact) if the protein is made into a rigid body.
#

import IMP.atom
import IMP.display

m = IMP.kernel.Model()
h = IMP.atom.read_pdb(IMP.atom.get_example_path("example_protein.pdb"),
                      m)
# residues 100 and 153 are two residues that are close together
# spatially, create a marker for the volume around them
s = IMP.atom.Selection(h, residue_indexes=[100, 153])
marker = IMP.atom.create_cover(s, "my marker")
m.update()

# if we now move the protein, marker will move along with it
rot = IMP.algebra.get_random_rotation_3d()
tr = IMP.algebra.Transformation3D(rot, IMP.algebra.Vector3D(-10, 10, 10))
IMP.atom.transform(h, tr)
m.update()

# display it to a file
w = IMP.display.PymolWriter("marker.pym")
g = IMP.core.XYZRGeometry(marker)
g.set_color(IMP.display.Color(0, 1, 0))
gp = IMP.atom.HierarchyGeometry(h)
gs = IMP.atom.SelectionGeometry(s)
gs.set_color(IMP.display.Color(1, 0, 0))
w.add_geometry(g)
w.add_geometry(gp)
w.add_geometry(gs)