LISP routine for interpolating elevation

[Anonymous]

I have only been using LISP for a few weeks now and I would like some advice. 

This is what I want to be able to do with this lisp routine:

- enter two points with elevations

- enter a number of points at random intervals in between those, with no elevations

- find the elevations of all the points between the first two elevated points

I am using autocad civil 3d lt 2012. 

I think I would be able to do this using simple math, but the points are not spaced evenly. 

Thank you 

[Jeff_M]

Using the first 2 points, calculate the slope between them. Then find the 2d distance from the first point to each of the points to find the elevations and apply the slope to the distance. Add the result to the first point's elevation. It really is just simple math, done a number of times.

[hencoop]

Jeff has the answer.  Be sure to get the 2D distance between the points for your slope calculation.  (drop or zero any point z-values)