[R] General Solution to Drawing a Spline Curve in 3d?

[Bryan Hanson]

Hello Again...

I know that R has plenty of functions for drawing splines between two  
points in 2d, and plenty of ways to fit a spline curve among various  
points in 2d or 3d (I think), but, is there a function which can be  
used to draw a simple spline curve between any two points in 3d  
space?  Since such a spline curve would be fundamentally a 2d object,  
I imagine that if a 3d version exists it would have to have some sort  
of argument specifying where that 2d plane should be drawn (maybe in  
cylindrical coordinates?).

What I'm looking for would be the 3d analog of grid.curve or xspline.   
What I'm trying to do is related to the idea of great circles, as  
implemented in package geosphere, but the curves I'd like to draw are  
not on the surface of a sphere nor are they parts of a circle.

Thanks for any suggestions!  Bryan
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Bryan Hanson
Professor of Chemistry & Biochemistry