Geometry filter for only Cylinder in Rhinocommon

This is my first post, and very basic question in rhinocommon.

I am trying to my personal command which is to pick a cylinder and change its diameter.
On RhinoCommonGuides page there example like this;

const ObjectType geometryFilter = ObjectType.Surface | ObjectType.PolysrfFilter | ObjectType.Mesh;

Then, I went to ObjectType page in RhinoCommon API, but Cylinder is not on there.

I also found GetCylinder class, but I cannot use the class like GetObject class.

I would like to make script just like this,

const ObjectType geometryFilter = ObjectType.Cylinder;
GetObject go = new GetObject();
go.SetCommandPrompt(“Select a Cylinder”);
go.GeometryFilter = geometryFilter;

GetResult res = go.GetMultiple(1, 1);

If someone give me an advise for that, I would appreciate.


If I’m not mistaken:

Once a Cylinder is added to the document, it becomes a cylindical shaped brep. There is longer a link to the parametrics of the cylinder.

What you could do however is get the underlying surface of the cylinder shaped brep and test for it to be a cylinder with:

From there you can create a new cylinder.

Does that make sense


Hi @f.kato,
You can create your own custom filter by setting filter callback function using GetObject.SetCustomGeometryFilter() method as follows:

public bool MyCylinderFilter(RhinoObject rhObject, GeometryBase geometry, ComponentIndex componentIndex)
            if (geometry is Surface srf)
                Cylinder cyl;
                bool isCylinder = srf.TryGetCylinder(out cyl);
                return isCylinder;

            return false;

Then set it to your GetObject instance.

GetObject gO = new GetObject();

Thank you guys!
Now you lift up my motivation for studying rhinocommon.
Hope I will be the guy like you who helps people on this forum.

Have a great day!!!