This guide demonstrates how to add curvature circles using RhinoScript.

## Overview

Rhino’s Curvature command is very useful for analyzing the curvature at a point on a curve. This script shows how to add the circle to the document when the curve is picked (instead of just drawing it dynamically).

There is no option on the Curvature command for leaving the circle that it draw dynamically. But, with the help of a script, you can write a subroutine that will. The following example demonstrates how to do just this.

## Sample

Option Explicit

Sub CurvatureCircle
Dim crv, crv_pt, crv_t
Dim arr, crv_pl, pl

crv = Rhino.GetObject("Select curve for curvature measurement", 4, True)
If IsNull(crv) Then Exit Sub

Do
crv_pt = Rhino.GetPointOnCurve(crv, "Select point on curve for curvature measurement")
If IsNull(crv_pt) Then Exit Do

crv_t = Rhino.CurveClosestPoint(crv, crv_pt)
If IsNull(crv_t) Then Exit Do

arr = Rhino.CurveCurvature(crv, crv_t)
If IsNull(arr) Then
Rhino.Print("Unable to compute curve curvature.")
Exit Do
End If

crv_pl = Rhino.PlaneFromFrame(arr(0), arr(1), arr(4))
pl = Rhino.MovePlane(crv_pl, arr(2))