how to draw clouds in civil 3d

One of my users chosen me the other day asking if in that location was any way to convert our DTM surface into a DEM surface, every bit a client had chosen them request if it was possible.  The short answer to the question was yes, but let me review the fundamental differences in these formats before getting into the how-to of this task.  Both formats exist for the aforementioned primal reason – to capture a representation of the earth'southward surface.  What differs is the way each stores that data.

Format Differences

A DEM or Digital Elevation Model stores this data using a predefined grid of squares.  Thus imagine a piece of graph paper; at each point ii graph lines intersect, an pinnacle will be assigned.  This format is an effective way of representing surfaces, but due to it'south rigid nature isn't necessarily the best option for civil applied science design.  And it is with that we have our 2nd format – DTM or Digital Terrain Model.  Unlike a DEM, a DTM captures a surface through the use of a triangular irregular network.

In essence, rather than using squares to capture a surface, a DTM uses triangles.  At the corner of each respective triangle, an 10, Y, & Z elevation is captured and stored.  Since the triangular network is irregular, the Tin can is generally meliorate at capturing things like menstruation lines.

Overcoming Format Limitations

Although Civil 3D'due south native modeling format is DTM, it does have the ability to consign a surface to a DEM file.  In addition to the architectural differences between DEM and DTM surfaces, the DEM format only accepts metric coordinate systems.  International users don't necessarily have to worry about this detail, merely those using imperial coordinate systems will demand to convert their surface to a metric coordinate system.

Equally nosotros'll meet later the "Export to DEM" command within Civil 3D lists both the source coordinate system, and the coordinate arrangement to the to-be-exported DEM.  Mostly speaking whenever Civil 3D lists both an input and output coordinate system, y'all tin can assume Civil 3D will do the heavy lifting of converting from one system to some other.  Unfortunately the "Export to DEM" control is an exception to that rule.  Every bit stated in the Civil 3D help file:

With that said we'll have to perform the coordinate conversion manually.  For purposes of this mail I am going to use the LandXML format every bit a carrier to catechumen from one coordinate system to another.

Conversion Process

1. Right-Click on the surface proper name and select "Export LandXML"
   
2. Since all we're interested in is our surface, have the defaults and press [Ok] to salve your XML file.
3. Create a new drawing (File > New), and select a Metric drawing template (ie. _AutoCAD Civil 3D (Metric) NCS Extended.dwt)
4. Set up the datum of your new DWG file

1. From the Civil 3D Toolspace select the "Settings" tab.
2. Right-Click on the DWG name and select "Edit Drawing Settings"
   
3. Select an appropriate metric coordinate system
   

Import your XML surface past going to File > Import > Import LandXML.  Selecting your XML file from the resulting dialog.

From the "Prospector" tab of the Ceremonious 3D Toolspace, Right-Click on the surface name and select "Export to DEM"

Generally speaking yous can accept the defaults from the resulting "Export Surface to DEM" dialog.  One setting yous may experiment with is the "Grid spacing"; the larger the number the less accurate your DEM.  Aside from that, simply specify an output file name and printing [Ok].

Read more nearly using AutoCAD Map 3D to analyze DEM surfaces in my September / October 2007 AUGIWorld Article "Finding the 3D in Map 3D: Surface Visualization"

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Source: https://thecadgeek.com/blog/creating-a-dem-with-civil-3d/

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