# Why does changing the curve radius not produce smooth transitions when using Curve to Mesh?

I have a curve here where the curve points are given different values for Radius.

With these radii I want to control the extrusion of the curve when using Curve to Mesh, so that the mesh gets thicker or thinner.

This works very well, however I don't get smooth transitions but wherever I use different values for Radius, hard corners appear in the mesh that I wouldn't expect.

Why is this? How can I smooth the result?

The Curve to Mesh node uses the lineary interpolated values between the points, so a change in the radius from $$0 - 1 - 0$$, for example, will be displayed with a hard edge.

It is also very difficult to smooth the mesh afterwards, so you would have to change the radius along the curve points beforehand.

Exactly for such purposes the node Blur Attribute is available since version 3.5+.

This node smooths the values between a specified number (Iterations) of neighboring elements with a specified strength (Weight):

Depending on the nature of your curve, however, you would have to make sure that it has enough points at all, which is why you would usually have to give the curve a higher resolution with Resample Curve, Subdivide Curve and/or Set Resolution.

This is important because the number of points or the resolution of the curve always works in combination with the value for Iterations, because with this you control how many neighboring elements/points are used for smoothing:

(Changing Iterations from 0 - 250 - 0)

By the way, Blur Attribute is a pretty ingenious node, and is often underestimated or ignored.

With it you can also smooth the positions of points, for example:

Also in combination with a Noise this node can be very helpful and achieve interesting results.

Always note, however:
With many elements and a high iteration value this node also needs a lot of computing power! Therefore try to choose the use consciously, use the node sparingly and only as high iteration values as absolutely needed.

• Of course, you could also process the radii with a Map Range node (Set to Smooth Step or Smoother Step). However, radii with values higher than $$1$$ (even if they are changed with From Max and To Max) cannot be processed correctly then because this also changes the interpolation. The result is still nice in most cases.