Author Topic: Simplify a C3D DEM surface?  (Read 5052 times)

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CHulse

  • Swamp Rat
  • Posts: 504
Simplify a C3D DEM surface?
« on: June 01, 2023, 08:16:51 AM »
I have a surface in C3D created from a 1m DEM. It's very dense. I only need it for some visual topo and steep slope analysis (not for a design, just an FYI on the plan) so it doesn't need to be so detailed. The slope visualization is terrible as it is. Anyone have thoughts on a best method to reduce/simplify the surface to get the topo and steep slopes to display more smooth/simply?
Thanks
Cary Hulse
Urban Forestry Manager
Wetland Studies and Solutions

Civil 3D 2020 & 2023

wizman

  • Bull Frog
  • Posts: 290
Re: Simplify a C3D DEM surface?
« Reply #1 on: June 01, 2023, 08:38:01 AM »
Does turning on the level of detail help?

CHulse

  • Swamp Rat
  • Posts: 504
Re: Simplify a C3D DEM surface?
« Reply #2 on: June 01, 2023, 08:45:24 AM »
Thanks - Good thought, but I don't think so.
Per the help: "When you plot a drawing, the full detail of all objects will be included, even if level of detail mode is on."
Cary Hulse
Urban Forestry Manager
Wetland Studies and Solutions

Civil 3D 2020 & 2023

wizman

  • Bull Frog
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Re: Simplify a C3D DEM surface?
« Reply #3 on: June 01, 2023, 12:47:53 PM »
Convert the surface to DEM and use the Map tools in Civil 3D.  It might give better analysis and representation.

Edit:
I missed that it was originally from a DEM which can be used directly into Map.  Another idea, you can have overlapping two copies of the same surface.  Each having different styles.  One is showing the contours and the other surface contains only the shaded steep slopes from slope analysis.
« Last Edit: June 02, 2023, 01:07:59 AM by wizman »

CHulse

  • Swamp Rat
  • Posts: 504
Re: Simplify a C3D DEM surface?
« Reply #4 on: June 02, 2023, 07:11:29 AM »
That's exactly what I'm doing - 2 copies as separate xrefs, one showing contours and the other showing slope shading. The real issue was the density of the surface, it displayed very jagged contours and the slopes were crazy, all over the place. I've ended up simplifying the surface using the edit tools in the surface to reduce surface points (by like 95%) and apply smoothing. I think I have something workable now. I wasn't familiar with all the options for simplifying and smoothing - lots of options in the dialogs. So after much trial and error, I think I have a workable surface now. I guess my original question was about those tools and all the options - what's the best practice? I couldn't find much info on it.
Cary Hulse
Urban Forestry Manager
Wetland Studies and Solutions

Civil 3D 2020 & 2023

d2010

  • Bull Frog
  • Posts: 321
Re: Simplify a C3D DEM surface?
« Reply #5 on: June 02, 2023, 07:33:31 AM »
I have a surface in C3D created from a 1m DEM. It's very dense. I only need it for some visual topo and steep slope analysis (not for a design, just an FYI on the plan) so it doesn't need to be so detailed. The slope visualization is terrible as it is. Anyone have thoughts on a best method to reduce/simplify the surface to get the topo and steep slopes to display more smooth/simply?
Thanks


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MSTG007

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Re: Simplify a C3D DEM surface?
« Reply #6 on: June 02, 2023, 08:06:05 AM »
This is a good conversation. Just throwing out another idea.
Since this came from a DEM file, and from a plotting side you want it to be fast loading, etc.
Whey not create a cogo point grid that drapes onto the DEM, then create a surface from that.

Another idea, would be to do the same, then maybe from the DEM (point surface), explode the line work.
Use that as a basic xref. Then data refence the original DEM in with a surface display set to No Display.

Just some thoughts.
Civil3D 2020

wizman

  • Bull Frog
  • Posts: 290
Re: Simplify a C3D DEM surface?
« Reply #7 on: June 02, 2023, 12:27:13 PM »

Whey not create a cogo point grid that drapes onto the DEM, then create a surface from that.


I think this will create a better surface.  But I would use ArcGIS to put points in center of each DEM pixel and elevate each point to the correct DEM elevation.  Then have Civil 3D do the triangulation from those points. 

Rod

  • Newt
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Re: Simplify a C3D DEM surface?
« Reply #8 on: June 04, 2023, 07:35:12 PM »
What method you use will partly depend on whether you want GRID or TIN. From my testing a grid surface performs 10x better than a TIN.
Here are a couple of other options

Grid Surface
You could create a DEM from the surface with a greater spacing (export to DEM) then create a new grid surface from the new DEM
Use third party software like https://www.usna.edu/Users/oceano/pguth/website/microdem/microdem.htm to create a new DEM file with a greater spacing

TIN
Use simplify surface

Cheers, Rod.
"All models are wrong, some models are useful" - George Box

CHulse

  • Swamp Rat
  • Posts: 504
Re: Simplify a C3D DEM surface?
« Reply #9 on: June 05, 2023, 07:02:28 AM »
Thanks for the input everyone.
Cary Hulse
Urban Forestry Manager
Wetland Studies and Solutions

Civil 3D 2020 & 2023