====== Axes ======

===== Introduction =====

''Axes'' are geometric objects used by the [[doc:user:geometry:user:opérateurs]] (to do symmetries, rotations, ...) or by the objective function ''AngleValueExtractor'' (inclination of a geometry with respect to an axis - see[[doc:user:results:fobj]]).

===== Definition =====


''Axes'' are defined by two points or by a line:

  pt0 = Point(0,x0,y0,z0)
  pt1 = Point(1,x1,y1,z1)
  axe1 = Axe(pt0, pt1)

  line2 = Line(0, pt0, pt1)
  axe2 = Axe(line2)

As for ''[[doc:user:geometry:user:triedres]]'', points and lines can also be defined in the ''pointset'', the ''curveset'', and points can even be taken from the mesh using the reference ''meshpointset'':

  axe1 = Axe(pointset(1), pointset(2))
  axe2 = Axe(curveset(1))
  axe3 = Axe(meshpointset()(1), meshpointset()(2))

In this case, if the corresponding points, curves or nodes are moving, so will the axis.

===== Note =====

Sometimes, only one point of a moving axis is known. Indeed, the origin or end point can be moving, but the axis must remain along the same direction. In this case, only one point is given, and its direction is specified. This is done by defining the axis with he same point twice:

  axe1 = Axe(pointset(1), pointset(1))

The direction is set using the functions:

  axe1.setSymX0(x0)
  axe1.setSymY0(y0)
  axe1.setSymZ0(z0)

if the origin of the axis is known, and:

  axe1.setSymX1(x1)
  axe1.setSymY1(y1)
  axe1.setSymZ1(z1)

if the end of the axis is known. ''x0'', ''x1'', ''y0'', ''y1'', ''z0'' and ''z1'' define the axis orientation. For example, the x directon is defined by: 
''pointset(1).get1()-x0''.