Working with 3d buildings and models in Arc Scene

Working with 3d buildings and models in Arc Scene This workshop will cover the basics of creating and working with 3D data in Arc Scene. We will take a basic flat building foot print layer and create new 3D building models from them. These models can them be the input to 3D analysis operations such as shadow analysis, or as the basis for creating more detailed 3D models in software like SketchUp. Setting up the DEM •
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In the ArcScene Catalog side tab, open a new connection to the 3D_GIS_Workshop folder. Open the SF_3D_Data geodatabase and drag the SF_NED_10m elevation model into ArcScene. This is an elevation model of a portion of San Francisco city, but you’ll notice that it actually looks flat in ArcScene. Our first step is to set this up as a 3d surface. •
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Right click on the layer name and select Properties… Go to the Base Heights tab and set Elevation from surfaces to Floating on a custom surface. In the drop down bar select the SF_NED_10m later and hit OK. If the terrain you are modelling is relatively flat you can increase the Z scaling by adding a custom elevation factor. •
Under Properties in the Base Heights tab, change the Elevations from features value to 2. •
Now return the value back to 1. 1 Extrude basic footprints: Next we’ll add your building footprints and drape the over the terrain. •
From the SF_3d_data.gdb drag the SF_footprints feature class into the map and above the NED layer in the table of contents. Notice that you can see some of the building polygons but only those around the edges of the NED. Because they are represented as flat, the rest are hidden beneath the terrain. The next step will ‘lift’ the footprints and drape them over the terrain layer. •
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Right click on the SF_footprints layer and open the layer Properties > Base Heights tab. Set the Elevation from surfaces to Floating on a custom surface and choose the SF_NED_10m layer and hit OK. We now have 2d buildings on a 3d surface. But we want to see this look like a real city, with 3 dimensional buildings. We’ll start by ‘extruding’ the 2d footprints to look like 3d objects. •
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Right click on the SF_footprints layer and open the layer Properties > Extrusion tab. Check the box for Extrude features in layer. From here we have a couple of different options for how we extrude the buildings. We can set a uniform extrusion height by value, or we can apply an expression that reads a unique building height value from the footprints table of attributes or as groups of building height classes. Let’s start by setting a uniform height to all the buildings. The value entered here is always in whatever units the data projection are in (meters in this case). •
In the Properties > Extrusion tab, enter 30 for the Extrusion value, hit OK. 2 This extrudes all buildings to the same uniform height above the elevation surface. If the building footprint is draped at an angle over the surface, notice that the roof line is as well. We can adjust this by changing the Apply extrusion by setting so that roof lines are extruded to a set value above the max or min elevation value of the base footprint. This levels the roofline and creates a more realistic building model. •
In the Extrusion tab of the layer Properties, set the Apply extrusion by drop down to adding it to each feature’s min height. If you’re very lucky, or put in a lot work on the attribute table, you may have a building footprint dataset that includes real building heights in it. In this case we can actually model the city so each building is represented with its true building height. •
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In the Extrusion tab, select the calculator icon next to the Extrusion value window. From the Fields list choose diff_heigh, hit OK. Hit OK again in the Properties window. The result should be a new representation of the buildings set to their real heights above ground. 3 Convert footprints to 3d feature class: So far we’ve created what look like 3d buildings in the GIS. But as far as the software is concerned these are really still just 2d features with a cool 3d trick applied to them. If we want to do anything like analyze shadows, or import more realistic models, we need to convert these to a 3d feature layer called a multi-­‐patch. •
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Go to the Geoprocessing menu and open the Geoprocessing Options window. Make sure Background Processing is UNCHECKED. Next, open the ArcToolbox and 3D Analyst Tools. Go to Conversion and double click Layer 3D to Feature Class. Set the input feature class to SF_footprints Choose your project geodatabase and save the output file as SF_buildings_3d. Although the new layer looks just like the extruded footprints layer, ArcScene treats them differently. With the new layer we can now perform 3d analysis or swamp and modify our building models. Import a Sketchup Model: •
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Do a web search for SketchUp 3d Warehouse and click on the top result: https://3dwarehouse.sketchup.com/ Search for Transamerica in the upper right. A number of models for the Transamerica Pyramid in SF will turn up. Select the first record by Sebastian S. Click the download icon and save the file (Transamerica.skp) to your project folder. In order for ArcScene to correctly replace the model we need to convert the downloaded SketchUp file to the more universal COLLADA file format. 4 •
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Open the new 3d model in SketchUp, then Export as a new “Collada” file: File > Export > 3D Model… > COLLADA File. Back in ArcScene, add the 3D Editor tool bar (Customize > Toolbars > 3D Editor). In the 3D Editor tool bar select Start Editing then use the Select Features tool to select the footprint that corresponds woth the model we downloaded (tall grey box in downtown SF). In the 3D Editor dropdown select Replace With Model… and choose the new COLLADA file you created (Transamerica.dae). 5