Site Modeling - Trimming Contours imported from other programs

[Jeff Prince]

This is in response to a question in another thread, figured it should be its own thread....

 

Vectorworks has a hard time trimming imported contours, but there are some things you can do to make it easier.

 

#1, set your view to Top/Plan to avoid problems with the geometry or site model misbehaving during this editing procedure.  Even if Vectorworks "fixes" this in future versions, it is generally a good practice to orientate your view to something orthogonal to the edit when using automated 3D editing tools.

 

In the case of imported contours from other GIS or CAD programs, you first need to get all your contours converted from Polygons (2D) to 3D Polys.  This simultaneously fixes the issue of each contour being on a 3D plane and instead issues a correct Z elevation that occurs with some imports.  Some might say this is potato/potahto, but it makes a difference when you are building site models.

 

Next you have a choice on how to "trim" out the contours to focus on your area of interest and make the model more efficient for Vectorworks to handle.  I have named these  the Split Method and the Site Model Crop Method.  In either case, a rectangle will define your area of interest and serve as a boundary for some editing operations.  Pro tip - Make this rectangle a bit larger than the site model you hope to end up with, as this will make your contours and 3D surfaces look much nicer instead of the data abruptly ending at the site model crop.  Prior to doing any edits, it may be beneficial to run the Simplification and then Validation tools found in the Site Modeling menu.  This can make your data much faster to process, but will consume your time in manually refining the data.  It's still a good idea because you will save time over the life of the project with each site model update or edit.  Just keep in mind, each time you do a simplification, you will likely create validation issues like intersecting contours or contours that have overlapping endpoints.  You will need to correct those issues prior to site modeling for the best results.  Experience will give you a sense of the time commitment required to get things working correctly, do not underestimate this because bad site models can become a vortex of despair on your project if done incorrectly.

 

Split Method - Manually trim the contours using the split tool.

Concept-Use the tool you think you should, but in small steps to make Vectorworks happy.

Delete any contours which to not cross or fall within the study area, you don't need them if they won't be seen and this make processing faster.  Then, grab only the contours within or crossing the rectangle (which should be all the remaining contours at this point).  Next, split them by doing a cutline one side of the rectangle at a time in LINE SPLIT + SELECTED OBJECT mode of the Split tool.  Delete the unneeded portions of the contours and repeat your way around the rectangle. Vectorworks can't handle splitting a lot of complex contours simultaneously around a crop boundary like a rectangle.  Do it in QGIS or other GIS programs prior to export if you can, it's faster and easier.

 

Site Model Crop Method-this is a trick to get Vectorworks to crop your contours as most other programs do.

Concept - Make a site model out of the entire collection of contours and trim to your desired site model boundary afterwards.

First, deal with the source data as mentioned earlier.... Convert your contours to 3D Polys.  Use Simplify 3D Polys to make the polys more efficient.  Finish by validating the site model data to correct any problems created by the simplification process.

Next, generate a site model....Switch to Top/Plan view, grab the contours, and generate the site model.  You can then adjust the site model crop to your area of interest which will make things look like you want.

Finally, create a more efficient site model....  Select the site model you just created.  Change the Site Model's 3D Display to "3D Contours".  Change the view to Top instead of Top/Plan so the site model displays the 3D contours instead of a plan view.  Ungroup the Site model.  Magically, you now have cropped 3D contours.  Make a new site model with this cropped data and enjoy the accelerated performance of your site model.

 

In either case, if you were a good site modeler and included data outside your desired depiction of the land, you can now adjust your site model crop and enjoy the benefits of having data beyond your crop for nice smooth contours free of cliffs and jaggies.

 

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So, all this being said, you would really be better off using Points to build site models instead of contours.  Contours are simply a computer's best guess as to where an elevation exists based on what you feed it.  If you feed vectorworks point data, it will generate contours for you.  If you feed it contours, it treats each vertex of the contour as a point, which isn't really accurate in the grand scheme of things and makes your site model very slow.  Don't believe me?  Here's a video of a 6500' x 6500' mountain in Phoenix I modeled from LiDAR points.  Note how quickly it is to develop the site model, render with a geo image, and crop down as described above.  If you take any area and convert it to contours to rebuild a site model, the resulting contours will usually generate 10x the number of vertices as the original point data if your contour value is the same.  Switching to a finer level of detail for the contour interval and the number of points will become exponentially larger.  That's not making your work more accurate, it's just bringing your computer to its knees for no reason.  Although, if

you are trying to convince your boss to pop for a fancy computer, I guess I have now demonstrated how you can make your computer look "slow" 🙂

 

 

[Poot]

Great input! I would not have thought about this.

One big question is, how/where are you getting your source data with relatively clean points?

It is pretty common for municipalities/govt. to provide height data as surfaces, contours, or point cloud....and not so much cleaned up points. I haven't really worked with point clouds, so I am not sure if you're starting from there? From what I have seen they take quite a bit of cleaning to make them good for use.

[Jeff Prince]

1 hour ago, Poot said:

One big question is, how/where are you getting your source data with relatively clean points?

it depends on the project and what is available.  Surveys or scans I pay for include clean and classified points.  Government data is generally ok as a starting point, but involves lots of cleanup on my end.  Stuff I shoot myself with a phone or drone is pretty good, but takes time to deal with.

Edited April 14 by Jeff Prince

[LavenderGardens]

16 hours ago, Jeff Prince said:

That's not making your work more accurate, it's just bringing your computer to its knees for no reason.

You have said this more than once during our training sessions.  What a great thread, thank you for spending the time writing it!