Features with 2D geometry can be converted to 3D features by adding z-values to the geometry using three different geoprocessing tools of 3D Analyst extension, depending on the conversion goal and the data that is available.
There are three methods to convert existing 2D features to 3D features using geoprocessing tools of 3D Analyst extension:
Below is the introduction to these three methods and the geoprocessing tools to use in each method to perform conversion. Before running the tools, please verify that 3D Analyst extension is turned on by navigating to Customize > Extensions. Check 3D Analyst if it is not already checked.
Deriving z-values from attribute values
If the z-values of features, such as heights, are available as attributes of the 2D feature dataset, the attributes can be converted into z-values of the features to generate 3D features using the Feature to 3D By Attribute tool.
Interpolating z-values using a surface layer
If an underlying elevation surface, such as a raster, TIN, or terrain dataset surface, on which the 2D features reside is available, the Interpolate Shape tool can be used to interpolate z-values for the 2D features from the elevation surface.
Extruding features between surfaces
3D features can also be created by extruding 2D features between surfaces. For example, an energy company may want to create subsurface blocks between surfaces representing geological horizons. This is achieved by extruding between the two surfaces for a given polygon area to create a multipatch bounding volume. The tool could be used to extrude features between surfaces is Extrude Between.
For information about converting a 2D shapefile to 3D in ArcGIS 9.x see: How To: Convert a 2D shapefile to a 3D shapefile