First, two ArcGIS shapefiles, one for the terrain and one for buildings, need to be merged. Then we need to create polygonal surface mesh which will be used to create 3D volume mesh (much later).

Parts of this guide are taken from http://dmg.caup.washington.edu/Reports/GIS-to-3DS/index.html. Some minor details are changed.

1. Download sample data provided . Unzip the files.
2. Start ArcMap.
3. Click the Add Layer button.
4. In the Add Data menu, highlight and select both building_sample.shp and contour_sample.shp. Both of these shapefiles will be added to the Layers Manager (on the left of the screen) and appear in the main viewing window. You may want to drag the building_sample layer above the contour_sample layer so that the buildings appear above the contour lines.
5.  Since the area is very large, we will want to work with a smaller portion of the map. So we need to crop the area of the map we want to work with:
   1. Click on the contour_sample layer. Use the selection tool to highlight the areas you want to save into a separate shapefile.
   2. Right-click the layer name in the layers browser. Under the ‘Data’ menu, select ‘Export Data’
   3. Give the shapefile a new name and save it. When prompted, add the new layer to the current map and remove the old contour_sample layer (right-click the layer name and then Remove)
   4. Now click on the building_sample layer. This time, you can select only the buildings that intersect the contour lines. Under the ‘Selection menu’, click ‘Select By Location. In the ‘Selection By Location’ menu, select features from the building_sample layer that ‘intersect’ the features in the cropped contour layer.
   5. Once the buildings are selected, simply repeat the ‘Export Data’ instructions in steps 1,2 and 3. (above).
   6. Repeat this process with each layer you wish to work with (if you are doing only buildings and terrain, then you only need to do this twice.)
      It is important that each layer be saved separately into a shapefile (for this example, terrain in one shapefile, building footprints in another).
6. Convert terrain to 3D.  The general idea is to convert the contour lines to a TIN (Triangulated Irregular Network) . However, simply converting to a TIN  produces overly detailed geometries in which every point on every contour is connect to every other contour line. This is unnecessary, but there is a workaround which requires converting the contour to a TIN, then to a Raster format, then back to a TIN, in the process loosing some of the detail, but preserving the terrain characteristics.
   1. Click and highlight the terrain crop layer in the Layers manager on the left.
   2. In ‘Toolbox’, under the ‘3D Analyst’ , ‘Create/Modify TIN,’ select ‘Create TIN from Features’
   3. In the ‘Create TIN from Features’ menu, check the terrain crop layer, verify that the ‘Height source’ is set to ELEV, and give the tin a new name.
   4. The resulting TIN should appear on the screen. Remove the old terrain crop layer from the Layers manager (right-click on the layer name and select ‘Remove’).
   5. Click and highlight the new terrain crop tin layer in the Layers manager
   6. Under the ‘3D Analyst’ Toolbar, under ‘Convert,’ select ‘TIN to Raster’
   7. In the ‘Convert TIN to Raster’ menu, set the ‘Cell size’ to a setting that gives a reasonable number (5.37 is good) of Rows and Columns. There is no hard and fast rule for this, but something that is under 1000 Rows and 1000 Columns is safe. Generally speaking, the smaller the cell size, the more detailed the terrain. Next, give the new raster layer a name (such as contour_rast)
   8. The resulting Raster image should appear on the screen. Remove the old contour tin from the Layers manager (right-click on the layer name and select ‘Remove’).
   9. Click and highlight the contour_rast layer in the Scene Layers manager.
   10. Under the ‘3D Analyst’ Tools, under ‘Convert,’ select ‘Raster to TIN’
   11. In the ‘Convert Raster to TIN’ menu, set the ‘Z tolerance’ to a reasonable setting…again, there is no hard and fast rule for this, but something that is between 5 and 10 ought to work. The smaller the Z unit value, the more points in the TIN. Next, give the new TIN layer a name (such as contour_tin2)
   12. The resulting TIN should appear on the screen. Even though the TIN is less detailed version of the original contour, the features should be accurate enough for terrain modeling.
   13. Remove the old contour_rast layer from the Scene (right-click on the layer name and select Remove).

Create Terrain Triangles

Next, we need to convert tin layer to polygons (triangles). Do this by selecting (in the tool box) ‘3D Analyst Tools’ -> ‘Conversion’ -> ‘From TIN’ -> ‘TIN Triangle’. Save the new shapefile. From Layers manager, remove all files except for the terrain triangles and building footprints. Move building footprints above terrain triangles so that the buildings appear of top of the triangles.

Merge Shapefiles

We will now create one shapefile that contains both buildings and terrain triangles. The buildings will appear as holes in the terrain triangles (which will create some non-triangle polygons).

From the tool box select ‘Analysis Tools’->’Overlay’->’Erase’.  In ‘Input Features’ field pick the terrain triangles. In ‘Erase Features’ pick building footprints file. Name the resulting file and commit.

To associate this new file (containing cut-out buildings) with the buildings file, perform a union: from the tool box select ‘Analysis Tools’->’Overlay’->’Union’. Name the file and save.

All polygons created in this manner are oriented counter-clockwise.

I am going to use VB.NET for most of my ArcGIS experiments because almost all of the nice, finished, detailed examples of ArcGIS code are in VB.NET. At this point, I really do not want to deal with syntax issues.

Incidentally, while aimlessly roaming esri.com’s dominion, I came across ShapeFile Read/Write OCX & DLL for VB6 and .NET. Neat, I thought, let me see what you have inside.

The help file explains how you are to use the contents of this package (it is actually well documented ^.^). The top of the Help tree, where it says Contents, is a good point to start reading.

Pay attention! There are 3 things inside that zip file that you can use. One ocx and 2 dll files. You should use the ocx only if you intend to have forms in your .NET project (which I don’t). The dll file that does not have the word NET in it is the one for VB6.

Setup

1. Make a new Visual Studio VB.NET console project.
2. Copy ArcViewShapeFileDLLNET.dll somewhere inside your project folder (this is just the way I do it, it could really be anywhere).  Right click on the project in the VS Solution Tree and add a reference to this dll
3. Obtain a shapefile (you can hunt down your own or steal from somebody). I am assuming that you will be running in the debug mode, so copy all 3 parts of the shapefile (.shp, .shx, .dbf)  to “ProjectName/bin/Debug”. For all the details on the structure of shape files, check out Esri’s technical description.

Now you are ready to follow an example or two from the Help file to do something with the shapefile. Since the title of this post is “Reading Esri Shapefile”, I recommend you start with the example that deals with reading.

In order to access the library functions, you will need to create an object of its type. So yeah, don’t forget to do that:

Dim MyShape As New ArcViewShapeFileDLL.ShapeFiles