Wednesday, March 7, 2012

Interactive Terrain Shaping - Circular Dependencies

In an earlier post, I was using a series of steps which generated this error message:

I didn't know what it meant so I ignored it, at least for the time being.  Smita from Autodesk picked up on it on in an Autodesk discussion forum and was kind enough to explain what's going on.
In that earlier post I was creating a bounded plane and then using the same feature line from that bounded plane to project a fill grid.  This created a circular dependency.  In Smita's words:

  1. The flat bounded plane derives its extents from the feature line. (Bounded plane operation)
  2. The feature line derives its elevations from the flat bounded plane. (Fill Grid with infill operation)
The way I understand this is that the feature line is getting information from the same plane that it is giving information to - thus a circular dependency.  She goes on to explain that I should have used an unbounded plane and then projected the fill grid using the unbounded plane as the infill.  Now the feature line is only getting information from the plane by deriving its elevations from it.
So I gave it a try and of course it worked with no warning messages.  
The difference is, instead of this:
I have this:
The bounded plane is replaced by an unbounded plane.  In my earlier post, using a bounded plane was an extra step that I didn't need, in fact it was causing issues.  Since the feature line already establishes its own boundaries for the top of the fill area, there was no need to use it to contain the plane too.
So now I know.  Watch out for circular dependencies, and don't ignore the warning message when it appears.  
How cool is it that Smita, software engineer for the ITS feature is actively participating in the discussion board!?

1 comment:

  1. Are you no longer in the game of making tools for users? I was wondering if you dove into any Civil 3D 2017 tools?