Although our users can import contour lines for their area of interest directly from Plex-Earth, there are cases where these contour lines are produced from other software or local surveys. These contour lines can be very complex when transferred to AutoCAD, consisting of too many vertices. Thus, when Plex-Earth is trying to process them, for example, to create a terrain surface, it can result in AutoCAD slowing down or even freezing. As such a workaround must be performed for simplifying these polylines.
In this tutorial, the following two processes are presented:
Part A: Reduce Vertices of Existing Countour Polylines
Part B: Generate Terrain Mesh from Contours
Part A: Reduce Vertices of Existing Contour Polylines
The process of removing the unnecessary vertices of a polyline is called weeding.
Below is an example of a drawing with contour lines acquired from a local survey.
If we select one of these polylines, we can see that it consists of break lines, each one having a large number of points. This probably is already slowing down AutoCAD's performance.
Moreover, if trying to create a surface from these break lines, the number of triangles created will be quite high, thus resulting in AutoCAD freezing.
Actually, if we zoom in more, the vertices of our contour lines will become obvious.
As such, weeding these lines is the only solution for simplifying them.
To do that, we use the command MAPCLEAN (if you have AutoCAD Map 3D)
After, that, a window will appear.
Choose Select manually and select your contours then select Next.
📢 Note: If your Contour Polylines are too complex choosing all of them at once, may freeze AutoCAD. It is better to choose some of them at a time and then repeat.
Then select the Weed Polylines as the selected action and choose Next:
On the last window, select Modify Original Objects and then Finish.
If the contour polylines are too complex, we may need to apply the Weeding of Polylines multiple times, to achieve the simplicity we want.
Below you can see the difference in a contour line, by applying the process five times.
After applying the process to all our contour polylines as many times as needed, we can see that we can use AutoCAD without encountering performance issues.
📢 Tip: If you are using Civil 3D, you can use directly the command WEEDFEATURES, select your contours, and repeat as many times as necessary.
Part B: Generate Terrain Mesh from Contours
To Create a Terrain Mesh from our contour lines, we just choose Terrain From Objects from the Plex-Earth ribbon. Alternatively, we can type PXV_TERRAIN_FROMOBJECTS in the command line.
Now, Plex-Earth asks us to Select Points. Since we do not have any points available, we skip this step using the space bar.
Then, we are prompted to Select Breaklines. We select all the contour lines we want for our terrain mesh and press enter.
Moreover, we can Select Boundary. In this case, the white line is our boundary, so we select it and press enter.
Finally, we are asked to Select Holes, if any. We can skip this by using the spacebar again.
Plex-Earth will now create a Mesh Object, using our contours, as shown below.
📢 Tip: Enable Realistic View for better Visualization
We hope that you have found this tutorial on how to simplify polylines and create a terrain mesh, helpful. Feel free to contact us at support@plexscape.com for any questions you may still have.
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Compatibility includes:
AutoCAD, Civil 3D®, AutoCAD Map 3D, AutoCAD Architecture, AutoCAD Electrical, AutoCAD Mechanical, AutoCAD MEP, AutoCAD Plant 3D: 2026 , 2025 , 2024 , 2023 , 2022 , 2021 , 2020
BricsCAD (Pro, Mechanical, BIM, Ultimate): V25 , V24 , V23 , V22 , V21