![]() ![]() The above sequence is interpreted as five surfaces as follows: Triangle strip, triangle fan, ring, ring, ring, first ring, ring Any subsequent surface other than Ring breaks the sequence. Multipatch 1 - First Ring designates the start of a ring group. A multipatch can have a number of surfaces represented by ring groups, the different roles of the rings help to determine the one group from the next, and within each group, determine the structure of the surface.įollowing are some examples of using the roles of rings in the ring sequence of a group to define a surface. This is because it is affectively another surface, even though it is coplanar with the side-ring and the hole-ring.Įach group has a ring sequence, and in combination with the role of the rings in the sequence, a surface can be defined. If, for instance, there was another co-planar ring inside the hole mentioned above, this would be represented as another group. Instead, an additional ring would be added to one of the groups to represent the hole.Īnother rule is that there is only one group per outer ring. A hole in one of the sides of the cube would not alter the number of groups. This means, for example, that a closed cube would comprise six ring groups. One rule that is not enforced, but that should be followed when creating a ring group, is that all rings in a group are co-planar. The roles of rings are determined by the multipatch (they are not a property of the ring itself) Rings all have the same structure, but they have a special role when defining a multipatch surface. This means that you can directly modify points in triangles but in order to modify points in a ring, you must use IPointCollection :: UpdatePoint If the index points to a point in a (segment of a) ring, you get a reference to a copy of the point, otherwise you get a reference to the point directly. The main difference between the ring and the triangles for a developer is when using IPointCollection :: GetPoint(index) A ring works contextually with other rings to specify a surface, but it may also be its own surface. Triangle strips and triangle fans specify surfaces by themselves. Triangle fans are a sequence of connected triangles that each use the first point in the sequence as an apex 0,1,0,2,0,3,0,4.,0,n Triangle strips are a sequence of connected triangles 0,1,2,3,4.n that each build from their predecessor. A single multipatch may comprise combinations of triangle strips, triangle fans, and ring groups. In a multipatch there is one triangle strip, or triangle fan per surface, whereas there can be one or more rings per surface. These geometries may be Triangle Strips, Triangle Fans, or groups of Rings ( ring-groups ). DescriptionĪ multipatch is a series of three-dimensional surfaces that are represented as groups of geometries. Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server. ![]()
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