Topic: Determine Y value of a point along a polyline with a known X value.

[Eddie D.]

Using Autolisp, I need to determine the Y value of the coordinates of a point on a polyline where I already know the X value.
What I have is a list of X values and a "depth" associated with each. I want to locate a point on a polyline for each X value and insert a block at the "depth" below that point.
Does this make sense???

[T.Willey]

You can draw an xline, and then find the intersecting points with that and the polyline ( using the ActiveX method ' IntersectWith ' ), or you can use the ' inters ' lisp function, and test each polyline section to see if the two vertexes that define the section, and the two points along your x axis intersect.

[Eddie D.]

Thanks! Tim.

[Lee Mac]

Nice method tim - I was wondering how this would be answered.

My first thought would have been to move along the line with vlax-get-PointatParam/Dist and find a point whose x-value was within a tolerance of the desired value. But I much prefer your method.

Lee

[T.Willey]

Glad you guys like.