UR1 and Line Origin versus Start and End Point

My official vacation time has begun. I still have rather a backlog of important, pending, almost completed projects, unanswered blog comments, and unavoidable meetings, so I will be online now and then in spite of that.

I also want to keep us all updated on important little titbits such as the UR1:

Revit 2013 Update Release 1

The Revit 2013 Update Release 1 is now available for download and installation from the web and within the product through Communication Center. Here are links to the appropriate update pages:

The build identifier is 20120716_1115.

Here is a list of the API enhancements implemented in this update:

Meanwhile, here is a neat little interesting and basic geometrical Revit API question that arose last week:

Relationship of Line Origin, Start and End Point

Question: When examining the AnalyticalSurface of a floor in my sample model, I noticed that the Origin property of a certain Line instance is not equal to either of its end points returned by the EndPoint property (get_EndPoint method in C#).

Until now, I had assumed that the Origin property of a line is always equal to one of its end points.

Could you please clarify:

  1. What exactly is the definition of a line's Origin property?
  2. How does the line origin relate to its end points?

Answer: I already presented some basic facts on the Revit API lines, curves and their parameterisations from Scott Conover's AU 2009 class on analysing building geometry, which he has continued updating, most recently for the AEC DevCamp 2012 (finalised material).

To answer your questions directly:

  1. The line origin and direction define the location of the infinite unbounded line. The start and end point of the bounded line can lie anywhere along this line.
  2. The origin always lies somewhere on the infinite unbounded line. There is no guarantee that it will coincide with either the start or end point of the bounded line, though. The origin of a bounded line may even lie outside the bounded part of the infinite line.

I hope this helps clarify things.

Anyway, now I'm off to the sunny Provence!