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# Axes

## Introduction

Axes are geometric objects used by the Geometry/Mesh Operators (to do symmetries, rotations, …) or by the objective function AngleValueExtractor (inclination of a geometry with respect to an axis - seeFonctions Objectives).

## 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 Trihedra, 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. 