## Length Fixing

It is suggested that this constraint fixes the length of a curve that
has a start and an end (a spline or a bounded curve), but it is
applicable to line segments only in the current version of C3D Solver.
Length fixing is a dimensional constraint, so it permits to change the
length using the **GCE_ChangeDrivingDimension**() method.

```cpp
constraint_item GCE_AddLength(GCE_system gSys, geom_item curve, 
                                               GCE_dim_pars dPar);
```

It takes a constraint system **gSys**, a curve **curve**, and parameters
of linear dimension, and returns a new constraint descriptor.

This constraint is supported for the following curve types: line
segment, circle, spline, and bounded curve (GCE_BOUNDED_CURVE) based on
a line, circle, or spline.

A curve length is fixed using the method

```cpp
constraint_item GCE_FixLength(GCE_system gSys, geom_item curve);
```

It takes a constraint system **gSys** and a curve **curve**, and returns
a descriptor of a new constraint.

This constraint can be applied to all curves supported by GCE_AddLength
method.

Length fixing is a dimensional constraint, so it's possible to change
the length using the
[GCE_ChangeDrivingDimension](../../../TWO-DIMENSIONAL_DIMENSIONS/subsections/EN/Driving_and_Variational_Dimensions.md)
method.