I often need a soft 0 -> 1 transition function. So I made it using this mathematical fuction :

(a) parameter determines the speed of the transition ( its steepness ) (b) parameter determines where the transition occures.

soft transition math fuction

Here it is turned into a node :

soft transition node group

Then I tried to use it to compute the radius of a curve to make it softly transition between 0 & 1 :

sotf transition on a curve radius

Strangely, it is as if the "Transition Speed" parameter was clamped. All I get is a very slow transition. And I couldn't debug it : curve with tto slow a transiyion

If I increase the "Transition Speed" parameter, it stops having any effect above 9.

In fact it is a very useful node ( and it could be native ) ... so solving this would be great.

File :

Thanks for your help !


1 Answer 1


You have a default Bezier Curve which has only 2 control points. Check it in Edit mode. Since the x shift is 0.5 (=center of the curve), the first point gets a radius of 0.0 and the end point gets a radius of 1.0. It works as designed! :-)

I guess you expect something like the following. For this you need more control points (=more x values):

enter image description here

Try a Resample Curve node with Count 50. To see the effect more clearly, you can also add a Map Range node to scale the 0.0-1.0 range to a wider range. (A curve with a radius of 0.0 is not visible).

  • $\begingroup$ Thanks Blunder ! Now my question seems ridiculous. ... the radius is evaluated on control points and only there ... $\endgroup$
    – Nicolas
    Commented Nov 12, 2023 at 15:57

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