## Radius Fixing

Radius fixing constraint is applicable to circles and ellipses. C3D
Solver is unable to change circle or ellipse radius if radius fixing
constraint is set for the object. The application can work with this
constraint as with a driving dimension that permits to change the radius
using the **GCE_ChangeDrivingDimension**() method. As for circles, this
constraint is similar to a driving radial dimension that was described
in Item [Radial and Diameter
Dimensions](../../../TWO-DIMENSIONAL_DIMENSIONS/subsections/EN/Radial_and_Diameter_Dimensions.md).

A radius can be fixed by the following method:

```cpp
constraint_item GCE_FixRadius(GCE_system gSys, geom_item g
                               , coord_name cName = GCE_RADIUS)
```

Initial method call data are given below:

-   **gSys** is the geometric constraint system;

-   **g** is a circle/ellipse descriptor;

-   **cName** is the radius type that takes the following values:
    GCE_RADIUS is the default value for a circle; GCE_MAJOR_RADIUS or
    GCE_MINOR_RADIUS mean fixing the radius at the major or minor
    ellipse axis.

The method returns the constraint descriptor that fixes circle/ellipse
radius.