Interpolate

Interpolate is a simple wrapper around the Blender Smooth Tilt and Smooth Radius tools.

Warning

Blender uses the term Radius but what it really is, is per-Point Curve thickness.
Confusingly, per-object curve thickness is then also called Bevel Depth.

It's thickness, on the point level, and on the curve level. So you can adjust it per object, and modulate it per point.

Note

Interpolate will only appear in the CURVEmachine menu, if the active spline actually has points with different tilt or radius values.
And so, you should also have adjusted the depth or extrusion of your curve, or you won't be able to notice the effect, changing or interpolating a radius or tilt has on your selection.

The tool will by default interpolate both - radius and tilt - of the selected points, at the same time, unless disabled in the redo panel.

InterpolateProperties interpolate tilt and radius at the same time

Selection

  • one or multiple - ideally continously selected - points

Using Interpolate

Interpolate Radius

InterpolateRadius1 a simple arc, created with Blendulate

InterpolateRadius2 the end points' radii (aka thickness) adjusted using ALT + S

InterpolateRadius3 interpolating the arc's points

InterpolateRadius4 interpolating the arc's points using Blendulate

Note

Note that Blendulate will also automatically interpolate tilt and radius.
And notice how its behavior is differant than using Blender's native tools (or using Interpolate).

Blendulate will take the distance of the selection's end points to the point at the other end of either segment into account, to adjust the radius accordingly.
This creates a better interpolation in a sitation like this.

Interpolate on the other hand, will "pull in" the radius values of the unselected points.

Interpolate Tilt + Radius

InterpolateTiltRadius1 here the spline end points have been rotated(tilted), using CTRL + T

InterpolateTiltRadius2 running the Interpolate tool on the arc's poins

InterpolateTiltRadius3 running Blendulate on the arc's points

InterpolateTiltRadius4 subdividing the long end segments and running Interpolate on all points

Note

Again, it seems like Blendulate does a better job interpolating, but it won't always be an option.
You may want to interpolate over a section of points, that isn't an an arc or blend, that Blendulate can deal with. You may want to interpolate over multiple arcs perhaps, or over a straight section for instance.

Also, you can see how while the interpolation of Blendulate seems smoother, it also introduces signifant non-planar faces on the long end segments.

That's why I've then subdivided those end segments a few times, followed by running Interpolate again, which then created a very nice result.