ArcGIS Tutorial: Multipatch

　　What is a multipatch feature?

A multipatch feature is a GIS object that stores a collection of polygons that can represent the boundaries of a 3D object as a single row in a database. Polygons store texture, color, transparency, and geometry information that represents part of a feature. The geometry information stored in polygons can be triangles, triangular fans, triangular bands, or loops, as shown below.

　　

　　

　　

　　

All Multipatch stores Z-values as part of the coordinate system used to build polygons. Although you can use numeric feature attributes to establish a base Z-value model for a multipatch, this option may not support the same analysis and interaction options that are available when using embedded Z-values.

Some Multipatch features are considered closed, which means they correctly define the volume. Closed Multipatch can be used for other analysis tools, such as 3D Union and 3D intersect. To treat a multipatch as closed, the polyhedron must be constructed in the correct way. The feature must represent a distinct volume. The face that makes up the volume must have the same counterclockwise direction as its coordinates and participate in the shell that defines the volume. These polygons must not intersect each other, and there must be no spacing or white space in the shell. You can use whether a closed geoprocessing tool is used to verify that the Multipatch is closed correctly.

Examples of Multipatch features include textured buildings, light poles, trees, sub-surface formations, underground buildings, or some type of analytical surface.

　　How do I create a Multipatch feature class?

To create a new Multipatch feature class, simply select Multipatch features from the Type drop-down menu when defining the geometry of the feature class.

　　What does the Z-value mean?

Z-values are used to represent the shape and elevation of multipatch features. It can represent an absolute height or a height relative to the ground. Both methods are fully supported when displaying and analyzing a generated 3D feature class.

The units and planes of the feature class Z-values should be defined in the feature dataset where the feature class resides, if it exists, or in the feature class itself (if there is no feature dataset). If no units are defined, ArcGIS will assume that the units of Z match the units of X, Y. This assumption can cause problems, especially if the units of x, y are in geographic units (latitude-longitude).

　　How do I create Multipatch features?

Use geoprocessing tools to import existing 3D models into ArcGIS to create Multipatch features. The 3D layer to feature class Geoprocessing tool converts points symbolized by various model formats, such as SketchUp, Openflight, 3DS, or COLLADA, into a Multipatch feature class. The Import 3D file Geoprocessing tool can do the same thing, but it provides more import format options, such as VRML. In addition, you can use ArcObjects to construct Multipatch features in a procedural way.

ArcGIS Tutorial: Multipatch