Best Way to Assess Curvature Conditions: Show the Bounding Curve for the Curvature Comb

When assessing the curvature condition for a curve, it is important to know if you are presented with one of these situations:

1. Discontinuity
2. Contact (C0)
3. Tangency (C1)
4. Curvature Continuity (C2)

The curvature comb (Spline Tools/ Show Curvature Combs) is the perfect tool for that, but please be aware that you can enhance its visual feedback even more by showing the bounding curve for the combs.

Take a look at the picture shown in Fig. 1. Which side describes the curvature better? The one without bounding curves on the right or the one with bounding curves on the left?

Fig. 1

Using the bounding curve you can spot right away that:

• in the first example the normals to the 2 curves at the shared end point are not aligned (simple contact)
• in the second example there is a sudden jump in the radii/curvatures of the 2 curves (tangency)
• even though they look different, the curvature is continuous for the last 2 examples (at least C2 condition).

The setting that controls the visibility of the bounding curve for the curvature combs can be found in System Options > Sketch (Fig. 2).

Fig. 2