A new beginning

I’m starting a new project, or rather a new business…  Site Modelers, LLC.

Please stop by and check it out.

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A bit of history

Several years ago, in my final semester at East Tennessee State University, I had some free hours so I took Calculus III for laughs. There were times that I paid a lot of attention and learned a lot under Jeff Knisley, there were also a lot of times that I was distracted by the computer at my desk, the internet is such a means of escape. Regardless of my study habits at that time I did walk away with a better understanding of surfaces and I still find myself looking back at my notes. Although those notes have holes where my attention was elsewhere, lucky though you can find the course material available to everyone at http://math.etsu.edu/multicalc/ Give it a look, it is worth your time.

 

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Contouring Surfaces

I’ve been playing with some ideas, code and Carlson Civil Suite today and I’ve stumbled across an interesting issue with Carlson’s contour routine.

Given this equation for a hyperbolic paraboloid, For more information on this surface

And porting some code to VBA so everyone can follow along
[sourcecode language='vb']
Option Explicit
Public Sub Parabolid()
Dim x As Double
Dim y As Double
Dim z As Double
Dim a As Double
Dim b As Double
Dim pt As AcadPoint
Dim coords(2) As Double
Dim result As Double
a = 1
b = 1

For x = -10 To 10 Step 0.1
For y = -10 To 10 Step 0.1

z = x ^ 2 / a ^ 2 – y ^ 2 / b ^ 2

coords(0) = x: coords(1) = y: coords(2) = z
ThisDrawing.ModelSpace.AddPoint (coords)

Next y
Next x

End Sub
[/sourcecode]

And then triangulating and contouring with these options

Produces a couple of visible errors

After a trial run with the “Reduce Vertices” option turned off the results appear correct, or at least visually correct, I’ve not verified them.

So I’m left wondering why the reduce vertices option produced asymmetrical results.

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Carlson Software Surface Manager

How many times have you pieced together the spot elevation data on a set of plans, triangulated it and then contoured it only to find isolated areas where the triangulation routine did not quite get it right? I sometimes contour at ridiculous contour intervals searching for any small anomalies that won’t show up on a one or two foot interval but will show up in your parking lot while grading. So I like preparing DTMs and then contouring at an interval of 0.10 or 0.25 feet. This gives me the ability to pick out any hiccups that have resulted in the triangulation routine. Then I can use Carlson’s Surface Manager to manually add or delete any points, to swap edges or to even delete triangles. I was a bit shocked that this excellent tool wasn’t mentioned in any of the sessions that I attend at the recent Carlson User Conference. It works like this:

Once you have a tin file, you start the Surface Manager like this

 

 

Or you can click the corresponding icon on the Carlson Surface tool bar, either of which will yield

 

From here you first, Add a surface then highlight it and press Set Current. You may use the Properties button to launch a modified Triangulate and Contour dialog to setup how your surface will be treated on the screen. Pay special attention to the “Draw Slope Arrows” option, it can be a lot of help.

Now using these menu options, Add Point, Remove Point, Remove Triangle, Set Point Elevation, Swap TIN Edge and Add Breakline, you can tweak away at your tin, dynamically!

 

There isn’t a toolbar provided for these options but one is easily enough made, and if you pay attention to the command line you can pick-up a few other neat tricks.

 

 

 

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The Rath's

That last post got me to thinking, “What happened to Randall Rath?” Why didn’t we do a better job with VB Design and CAD Vault? The core members, of which I was one, could have done better, but we were complacent with the fact that Randall and Ralph would always take care of us. Randall and Ralph gave us so much and asked only that we gave a little in return. We failed both of them and ourselves.

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