Working with 3d Terrain in SketchUp

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SketchUp has a built-in tool for importing terrain, which used to be based on Google Earth's terrain data. Now it's based on a Digital Elevation Model (DEM) maintained by Trimble. The level of detail is adequate for providing context, but often we want to work with higher-quality terrain. Here we look at three different tools for importing high-detail terrain in SketchUp. Each provides higher detail terrain, but there are drawbacks in terms of setup time, availability of data, and resulting complexity in the model. We chose Portland's Goose Hollow and the US-26 tunnel (seen above and below) for a sample area because it's one of the least flat areas in Portland.

PortlandMaps

The highest level of detail we looked at is based on aerial Lidar scans (a mapping technique using GPS and laser rangefinding) provided by City of Portland through PortlandMaps. The result is an incredibly detailed map with 1 foot contour lines. We downloaded and processed these using QGIS, then imported into SketchUp and meshed using Fredo6's TopoShaper plugin. The contour lines and resulting mesh are shown below:

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DOGAMI

Another detailed Lidar-based map is available for much of Oregon through the Department of Geology and Mineral Industries (DOGAMI). Similar to the City of Portland's Lidar data, we used QGIS to download and process this data, and meshed the resulting contour map using TopoShaper. The result is a map with a 10 foot contour interval, shown below with a terrain mesh calculated with TopoShaper.

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PlaceMaker / CesiumIon

We're fans of mind.sight.studio's PlaceMaker plugin for SketchUp– we use it frequently to create buildings and streets when we need a low-detail context model of a large area. This summer, PlaceMaker Version 3 introduced some new features, including a higher detail terrain importer.

The terrain data is provided by CesiumIon - who use a mix of open and commercially available terrain data and some proprietary processing to provide variable quality, easily-streamed data for a variety of web apps and software. In this case, the resulting terrain is lower detail than the two Lidar sources, but better than SketchUp's built in terrain.

When importing terrain, PlaceMaker presents a choice of grid spacing. The smaller the grid size the more detailed the terrain import– up to a point. The example shown above used a 30 foot grid spacing. Below, we tested a terrain import at a tiny, 10' grid spacing to see how detailed the terrain data is.

(This example is the west portal of the US-26 tunnel under Vista Ridge in Portland. It's there if you know what you're looking for, but neither data set is detailed enough to make it obvious. See the reference image below to get oriented)

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Here's the same area for reference, using the high-detail Lidar scan and an aerial photo from NearMap.

The result (above, compared with SketchUp's built-in terrain importer) shows markedly higher detail– and also hints at CesiumIon's terrain simplification algorithm. While PlaceMaker has resampled the terrain data into the requested 10' triangular grid, the underlying data appears to be an unstructured grid– a technique to increase detail while reducing the number of lines and faces–that gets lost upon import to SketchUp. A tighter mesh increases detail only up to a certain point– in our experiments, grids smaller than 30' did not increase detail.

So Which Is the Best?

The answer is, it depends. We rarely need to work with terrain at the level of detail available through PortlandMaps, and the extra complexity slows down our model. But it's useful to have a few options available so we can choose an appropriate level of detail for a particular model.

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Joel is a designer at Fat Pencil Studio