Constraints
Introduction
In the data tree of Flux the node Solver > Optimization > Constraints allows
the user to define some constraints which are structural or physical limitations
imposed by the optimizer, a constraint allow the user to control the shape of the
design with some symmetries constraints, volume values constraints or physical
limits. The short list of the constraints is given below:
Constraints  Required information 

Physical constraint 

Constraints on 2D faces volume 

Symmetry constraint (defined by direction) 
In this case, the direction of the symmetry axis is
(0.5;0.5).

Symmetry constraint (defined by angle) 
In this case, the angle of the symmetry axis is
45°.

Double symmetry constraint (defined by direction) 
In this case, only one of both axes must be defined,
choose between (1;0) for X axis or (0;1) for Y axis.

Double symmetry constraint (defined by angle) 
In this case, only one of both angles must be defined,
one can choose between 0, 90, 180, 270, ….
