File: Part_Document_Scripts/Measure_Curve_With_3_PTS_AS_CIRCLE.py
Version: 1.6
Document Type: Part (also works with Part inside Product or Process)

Measures the effective radius and diameter of a curve by placing three points on it and fitting a circle through them. The result is displayed in a message box. All construction geometry is deleted after measurement.

See Measure Curve With 3 Points As Circle Keep Con to keep the construction geometry.

1. Open a CATPart document containing a curve to measure
2. Run the script
3. Select the curve to measure — click OK when done
4. A message box displays the result

A message box showing:

Radius: 25.43mm
Diameter: 50.86mm

If the curve is straight (points are collinear):

Radius: 0mm
Diameter: 0mm
Curve appears to be straight
Points are colinear

All construction geometry (extracted curve, points, circle) is deleted after the result is shown.

1. The curve is extracted and converted to a datum
2. An extremum point is created along direction (1, 2, 3) to serve as an anchor
3. Three points are placed at 20%, 50%, and 80% along the curve anchored to the extremum
4. The datum points are checked for collinearity — if collinear the curve is straight and the script exits
5. A circle is fitted through the three datum points and the radius is measured

• The measurement is an approximation — accuracy depends on how circular the curve is
• Results are rounded to 2 decimal places
• For a surface radius measurement see Measure Radius Surface