Creating a spline between two curves


Hi guys! I’m stuck and would need help… In the attached file I’d like to create a spline between the endpoints of the curves (at the points). The radius of the spline should change smoothly from 1600 mm to 10000 mm (the radius of the curves) and be G1 (or G2) to the curves. Possible? I haven’t found a solution yet… Position continuity would be ok if G1-G2 isn’t possible.


Spline.3dm(54.6 KB)



I don’t think it’s possible (I may be wrong, though).

Reason: The curvature of the left curve (1/1600mm) is higher than the right (1/10000mm). So you want the curvature to drop from the left to the right. But you actually need to increase it, if you want the left curve to connect to the right one. Imagine you just keep the curvature of the left curve the same. Even then you wouldn’t hit the right curve when making the left one longer (you would end up below the right curve). So somewhere between the curves you need to increase the curvature, something you don’t want.



Hmmm, yes, I guess I have to forget the G1-G2 part… Still, creating a spline with a radius of 1600 mm at the (left) start point and 10000 mm at the endpoint seems to be difficult…



It depends what you mean by “change smoothly”. If you want a curve that goes smoothly from 1600R down to about 500R and back up to 10000R just make a curve blend using curvature continuity…
If you want it to monotonically transition from 1600R to 10000R (always increasing) then you are going to have to settle for G0 continuity. In the enclosed file are a couple curves that might be close to what you want.

SplineX.3dm(57.2 KB)


Hi Jim! Yes, blend was the first thing I tried - not what I need. G0 is ok.
Thanks for the file! I think the curves are close enough :smiley:



I was just informed of the arc blend command on another post. Wouldn’t that get you closer to what you were after.


Interesting command… I haven’t used it before - nice! It doesn’t seem to help with this problem, though…
Thanks anyway!