Creating a new string having vertices perpendicular to a reference string?

[michaelv976]

First time poster. New to C3D. Tried using the search but not sure if my key words are just wrong. Apologies for the rather lengthy description leading into the question.

I am working on an inhouse drainage related spreadsheet that relies on x,y,z values for 4 strings (as a min) to run calculations for surface flows along a road corridor. For the purposes of this post I'll refer to them as Left Kerb (LK), left shoulder (LS), right kerb (RK) and right shoulder (RS). The reference line (Ref) is generally one of these four and used to create the other three. As a consequence the vertice points are perpendicular to each other (typically) and if I extract the vertice data from genio.txt files it works well with formula in the spreadsheet. My problems start where ramps enter/exit the main alignment.

The below image shows an exit ramp (LHS driving conditions). Runoff flow arrows sketched in blue. As it flows along the kerb right of image to left of image, the catchment width changes from being just the main alignment (W1) to being the main alignment plus ramp (W2) at the point where the kerbed ramp nose starts. The LK and LS strings used for the spreadsheet are the white circles ones. Upstream of the nose the LK and LS strings are developed from the main alignment RS (Ref) string. Downstream of the nose however the LK and LS strings are developed from a different Ref string. As such the downstream vertice points are not perpendicular to the main alignment RS string. They revert back to matching the main alignment downstream of where the ramp commences.

To make my spreadsheet more accurate I need to develop new LK and LS vertice points (sketched red circles) that are perpendicular. I acknowledge there are minor anomalies that result from using the main alignment string to create 'perpendicular' vertice points on a skewed string, these are within my tolerances.

Example 1: Diverging ramp

Another example (image below) is where three of the strings are new design strings and the fourth is an existing string (say draped from survey). The vertice points for the draped string is not perpendicular to the reference string. Again the red circles represent the location where I need 3d vertice points.

My extremely time consuming work around is to draw 3d polylines between perpendicular strings then extend them to the string I need a matching perpendicular vertice for. Then I am effectively 'listing' these extended polylines to grab the data from. I would like to establish if there is a way to create a new string, using strings already in the model, that has its vertice points effectively stripped and replaced with vertice points that are perpendicular to the main alignment reference string.

I hope this long winded description makes sense?

Thanks,

Mike

At this stage 

[michaelv976]

Just noted that the second image did not get included. This was it...

[TerryDotson]

Won't the OFFSET command provide this object?

[michaelv976]

Thanks for the reply.

Talking purely from an ACAD levelof experience here, I'm not aware that offset works with 3d polylines. So unless I'm mistaken, creating then offsetting a 2d poly will get me the perpendicular vertice points but I'd then have to write code in excel to extrapolate the z's. 

If the offset was consistent then this would probably be the next best alternative. However  even in that second image example there's a bit of drift, with the line in question varying from about 0.85m to 1.7m (offset) over the 3km length being assessed. It certainly would not work for the first example where ramps merge/diverge at ever changing offsets.

Apologies if there's a completely different offset in C3D you're referring to?

[wfberry]

I believe the offset commands for feature lines work with 3D polylines as well.

Bill