Geometry

• Engine
• ArcGIS for Desktop Basic
• ArcGIS for Desktop Standard
• ArcGIS for Desktop Advanced
• Server

• About geometry objects
• About spatial references and coordinate grids
• Using geometry objects
• GeometryServer
• BufferConstruction
• Using spatial reference objects
• Using transformation objects

About geometry objects

About spatial references and coordinate grids

For further information see:

Using geometry objects

• How to create a multipoint
• How to create a multipoint object from the vertices of a polyline

Multipatches support the IRelationalOperator3D interface, which contains the Disjoint3D method, and the IProximityOperator3D interface, which has methods for reporting the nearest distance from a query geometry to the multipatch and the nearest point on the multipatch from a query geometry. These interfaces treat multipatches as a collection of surfaces with no interior, so if you have a multipatch in the shape of a cube, and a point apparently inside that cube, the point will be classified as disjoint because it's not intersecting any of the cube's sides.

Multipatches contain multiple parts: triangle strips, triangle fans, triangles, and rings. Rings are the same Component Object Model (COM) object type as used in polygons but are unconstrained by 2D validity rules, so they can be vertical or have vertical segments. Each part in a multipatch has the following additional properties:

• Type - TriangleStrip, TriangleFan, Triangle, Outer Ring, and so on.
• Priority - Controls the drawing order of overlapping parts.
• An index into the array of materials (see the Material and textures section).

You can extrude polylines and polygons in various ways to define multipatches, or construct them explicitly (see the IConstructMultiPatch and IExtrude interfaces on the GeometryEnvironment singleton object). Multipatches can be stored as the geometry for a feature or used to symbolize points by drawing 3D models at the locations of the points. You can specify per-vertex normals to orient faces and provide more control over how multipatches are lit. Multipatches can contain materials (specifying color, texture, and transparency information) and texture coordinates that specify the placement of textures on each part. ArcScene provides style galleries containing multipatch models for 3D buildings (industrial and residential), trees, vehicles, street furniture, and other thematic categories.

You can compute the volume of a multipatch. The number will be meaningful if the multipatch is a closed surface (or has an opening that forms an implied lower face). You can compute the tessellated surface area using IArea3D. You can project a multipatch onto a plane (usually the xy plane). This operation is used to generate multipatch footprints when multipatches are operands to a spatial relation method. A ray can also be intersected with a multipatch.

Triangle strip

A triangle strip is a type of surface patch, defined by a collection of points that specify the triangle surfaces that comprise it. For a triangle strip with six points, the triangle surfaces are defined by points: (0, 1, 2), (2, 1, 3), (2, 3, 4), (4, 3, 5). The front side, or face, is established by orienting the first three vertices clockwise. See the following illustration:

Triangle fan

A triangle fan is a type of surface patch defined by a collection of points that specify the triangle surfaces that comprise it. Unlike a triangle strip, a triangle fan is comprised of a set of 3D triangles where the first point defines the apex or origin point and is included in all of the triangle surfaces. For a triangle fan with six points, the triangle surfaces are defined by points: (0, 1, 2), (0, 2, 3), (0, 3, 4), (0, 4, 5). The front side is established by orienting the first three vertices clockwise. See the following illustration:

Triangle

A triangle part is a type of surface patch used to construct a multipatch, defined by a collection of points that specify the triangle surfaces that comprise it. Each consecutive triplet of vertices defines a new triangle, and the vertex count must be a multiple of three. For a triangle part with six points, the triangle surfaces are defined by points: (0, 1, 2), (3, 4, 5). The front side of each triangle is established by orienting its vertices clockwise. See the following illustration:

Rings (as used in multipatches)

Rings are used in polygons and in multipatches. Rings in multipatches are not constrained by 2D validity rules, so you can use a multipatch containing vertically-oriented rings to represent vertical walls. A given ring does not have to be planar. That is, the vertices do not have to all lie in one plane. The interior of a non-planar ring is defined by how it is tessellated, which is currently done by the OpenGL utility library tessellator. A group of rings in a multipatch can define a surface with holes. A ring type is assigned to the ring immediately after it has been added to the multipatch as follows:

• Outer Ring - Exterior or outer ring of a multipatch surface (analogous to an outer ring in a polygon).

• Inner Ring - Interior or hole within a multipatch surface (analogous to an inner ring in a polygon).
• First Ring - First ring of a group of rings with an unspecified containment relation.
• Ring - Another ring of a group of rings with an unspecified containment relation.

For further information see:

GeometryServer

wsdl.exe /sharetypes /language:CS /namespace: ArcGISWebServices /out:.\ArcGISSOAP_SharedObjects.cs /protocol:SOAP http://geometria/arcgis/services/MapService/MapServer?wsdl http://geometria/arcgis/services/Geometry/GeometryServer?wsdl

// This C# example illustrates using a Geometry Service to compute the areas of polygons obtained 
// from a Map Service.

using System;
using System.Collections.Generic;
using System.Text;
using ArcGISWebServices;

namespace GSClientTest
{
    class Program
    {
        static void Main(string[] args)
        {
            ArcGISGeometryServer gs=new ArcGISGeometryServer();
            gs.Url="http://geometria/arcgis/services/Geometry/GeometryServer";
            ArcGISMapServer ms=new ArcGISMapServer();
            ms.Url="http://geometria/arcgis/services/States/MapServer";

            // Ask the "States" Map Service for all features in the first layer, which is assumed 
            // to be a polygon layer.
            QueryFilter qf=new QueryFilter();
            qf.SubFields="*";
            RecordSet rs=ms.QueryFeatureData("Layers", 0, null);

            // Find the geometry field in the returned record set, and get the spatial 
            // reference for the record set.
            SpatialReference sr=null;
            int iGeometry;
            for (iGeometry=0; iGeometry < rs.Fields.FieldArray.Length; iGeometry++)
            if (rs.Fields.FieldArray[iGeometry].Type ==
                esriFieldType.esriFieldTypeGeometry)
            {
                Field f=rs.Fields.FieldArray[iGeometry];
                sr=f.GeometryDef.SpatialReference;
                break;
            }

            int j;
            Geometry[] aG=new Geometry[rs.Records.Length];
            for (j=0; j < rs.Records.Length; j++)
                aG[j]=(Geometry)rs.Records[j].Values[iGeometry];

            Geometry[] aGDens=gs.Densify(sr, aG, 0.1, false, 0.0);

            // Project the geometries to an equal area projection to calculate their areas.
            // The queried spatial reference (2163) is a US National Atlas Lambert  
            //  Azimuthal Equal Area.
            SpatialReference projSR=gs.FindSRByWKID(null, 2163, 0, true, true);

            Geometry[] aGProj=gs.Project(sr, projSR, false, null, null, aGDens);
            double[] lengths=new double[rs.Records.Length];

            // Cast the array of geometries to an array of polygons.
            Polygon[] aP=new Polygon[rs.Records.Length];
            aGProj.CopyTo(aP, 0);

            double[] areas=gs.GetAreasAndLengths(sr, aP, out lengths);
            System.Console.WriteLine();
        }
    }
}

Module Module1

Sub Main()
    
    Dim gs As ESRI.ArcGIS.Geometry.IGeometryServer
    gs=New ESRI.ArcGIS.Geometry.GeometryServerImpl()
    gs.Url="http://geometria/arcgis/services/Geometry/GeometryServer"
    Dim ms As ESRI.ArcGIS.Carto.MapServer
    ms=New ESRI.ArcGIS.Carto.MapServerClass()
    ms.Url="http://geometria/arcgis/services/States/MapServer"
    
    'Ask the "States" Map Service for all features in the first layer, which is assumed
    'to be a polygon layer.
    Dim qf As ESRI.ArcGIS.Geodatabase.IQueryFilter
    qf=New ESRI.ArcGIS.Geodatabase.QueryFilter()
    qf.SubFields="*"
    Dim rs As ESRI.ArcGIS.Geodatabase.IRecordSet
    rs=ms.QueryFeatureData("Layers", 0, Nothing)
    
    'Find the geometry field in the returned record set, and get the spatial
    'reference for the record set.
    Dim sr As ESRI.ArcGIS.Geometry.ISpatialReference
    sr=Nothing
    Dim iGeometry As Integer
    For iGeometry=0 To rs.Fields.FieldArray.Length - 1
        If (rs.Fields.FieldArray(iGeometry).Type=ESRI.ArcGIS.Geodatabase.esriFieldType.esriFieldTypeGeometry) Then
            Dim f As ESRI.ArcGIS.Geodatabase.IField
            f=rs.Fields.FieldArray(iGeometry)
            sr=f.GeometryDef.SpatialReference
        End If
    Next iGeometry
    
    Dim j As Integer
    Dim aG(rs.Records.Length) As ESRI.ArcGIS.Geometry.IGeometry
    For j=0 To rs.Records.Length
        aG(j)=rs.Records(j).Values(iGeometry)
    Next j
    
    Dim aGDens As ESRI.ArcGIS.Geometry.IGeometryArray
    aGDens=gs.Densify(sr, aG, 0.1, False, 0.0)
    
    'Project the geometries to an equal area projection to calculate their areas
    'The queried spatial reference (2163) is a US National Atlas Lambert
    'Azimuthal Equal Area.
    Dim projSR As ESRI.ArcGIS.Geometry.ISpatialReference
    projSR=gs.FindSRByWKID(Nothing, 2163, 0, True, True)
    Dim aGProj As ESRI.ArcGIS.Geometry.IGeometryArray
    aGProj=gs.Project(sr, projSR, False, Nothing, Nothing, aGDens)
    'Cast the array of geometries to an array of polygons.
    Dim aP(rs.Records.Length) As ESRI.ArcGIS.Geometry.Polygon
    aGProj.CopyTo(aP, 0)
    
    Dim lengths As ESRI.ArcGIS.esriSystem.IDoubleArray
    Dim areas As ESRI.ArcGIS.esriSystem.IDoubleArray
    gs.GetAreasAndLengths(sr, aP, areas, lengths)
End Sub

End Module

BufferConstruction

• The IBufferConstructionProperties interface provides several new options for construction of geometric buffers.
• Polyline buffers can be constructed to the left or the right of the polyline.
• Polygon buffers can exclude the interior of the polygon.
• Curve segments can be added to the output buffers.
• Buffers can be dissolved together in places where they overlap.
• Separate polygons can be unioned for each non-overlapping portion of a buffer.
• True geodesic buffers can be generated around points that are in a GCS.
• Geometries of different types can be buffered together.
• Multiple buffers can be generated around the same set of inputs.
• In the context of a single buffering operation, different features can be buffered by different distances.

Using spatial reference objects

• Using the SpatialReferenceEnvironment
• Constructing a high- or low-precision spatial reference
• Converting between high- and low-precision spatial references
• How to import or export a spatial reference

// Smart pointer variables used.
IDatumPtr ipDatum;
IPrimeMeridianPtr ipPrimeMeridian;
IUnitPtr ipUnit;
IAngularUnitPtr ipAngularUnit;

// Create the factory and the component parts.
ISpatialReferenceFactoryPtr ipFactory(CLSID_SpatialReferenceEnvironment);
ipFactory->CreateDatum(esriSRDatum_OSGB1936, &ipDatum);
ipFactory->CreatePrimeMeridian(esriSRPrimeM_Greenwich, &ipPrimeMeridian);
ipFactory->CreateUnit(esriSRUnit_Degree, &ipUnit);
IGeographicCoordinateSystemEditPtr ipGeoCSEdit(CLSID_GeographicCoordinateSystem)
  ;
IGeographicCoordinateSystemPtr ipGCS;

// Cast for the AngularUnit from the Unit.
// (This is achieved by the SmartPointers.)
ipAngularUnit=ipUnit;

// Make the string descriptions.
CComBSTR name(_T("User Defined Geographic Coordinate System"));
CComBSTR alias(_T("UserDefined"));
CComBSTR abbreviation(_T("User"));
CComBSTR remarks(_T("User Define GCS based on OSGB1936"));
CComBSTR useage(_T("Suitable for the UK"));

// Make the call.
HRESULT hr;
hr=ipGeoCSEdit->DefineEx(name, alias, abbreviation, remarks, useage, ipDatum,
  ipPrimeMeridian, ipAngularUnit);
// Cast for the result.
ipGCS=ipGeoCSEdit;

IDatum ipDatum;
IPrimeMeridian ipPrimeMeridian;
IUnit ipUnit;
IAngularUnit ipAngularUnit;

// Create the factory and the component parts.
ISpatialReferenceFactory ipFactory=new SpatialReferenceEnvironmentClass();
ipDatum=ipFactory.CreateDatum((int)esriSRDatumType.esriSRDatum_OSGB1936);
ipPrimeMeridian=ipFactory.CreatePrimeMeridian((int)
    esriSRPrimeMType.esriSRPrimeM_Greenwich);
ipUnit=ipFactory.CreateUnit((int)esriSRUnitType.esriSRUnit_Degree);

IGeographicCoordinateSystemEdit ipGeoCSEdit=new GeographicCoordinateSystemClass();
// Cast for the AngularUnit from the Unit.
ipAngularUnit=ipUnit as IAngularUnit;

// Make the string descriptions.
string name="User Defined Geographic Coordinate System";
string alias="UserDefined";
string abbreviation="User";
string remarks="User Define GCS based on OSGB1936";
string useage="Suitable for the UK";

// Make the call.
ipGeoCSEdit.DefineEx(name, alias, abbreviation, remarks, useage, ipDatum,
    ipPrimeMeridian, ipAngularUnit);
// Cast for the result.
IGeographicCoordinateSystem ipGCS=ipGeoCSEdit as IGeographicCoordinateSystem;

Dim ipDatum As ESRI.ArcGIS.Geometry.IDatum
Dim ipPrimeMeridian As ESRI.ArcGIS.Geometry.IPrimeMeridian
Dim ipUnit As ESRI.ArcGIS.Geometry.IUnit
Dim ipAngularUnit As ESRI.ArcGIS.Geometry.IAngularUnit

'Create the factory and the component parts.
Dim ipFactory As ESRI.ArcGIS.Geometry.ISpatialReferenceFactory
ipFactory=New ESRI.ArcGIS.Geometry.SpatialReferenceEnvironment()
ipDatum=ipFactory.CreateDatum(ESRI.ArcGIS.Geometry.esriSRDatumType.esriSRDatum_OSGB1936)
ipPrimeMeridian=ipFactory.CreatePrimeMeridian(ESRI.ArcGIS.Geometry.esriSRPrimeMType.esriSRPrimeM_Greenwich)
ipUnit=ipFactory.CreateUnit(ESRI.ArcGIS.Geometry.esriSRUnitType.esriSRUnit_Degree)

Dim ipGeoCSEdit As ESRI.ArcGIS.Geometry.IGeographicCoordinateSystemEdit
ipGeoCSEdit=New ESRI.ArcGIS.Geometry.GeographicCoordinateSystem()

'Cast for the AngularUnit from the Unit.
ipAngularUnit=ipUnit

'Make the string descriptions.
Dim Name As String, _alias As String, abbreviation As String, remarks As String, useage As String
Name="User Defined Geographic Coordinate System"
_alias="UserDefined"
abbreviation="User"
remarks="User Define GCS based on OSGB1936"
useage="Suitable for the UK"

'Make the call.
ipGeoCSEdit.DefineEx(Name, _alias, abbreviation, remarks, useage, ipDatum, ipPrimeMeridian, ipAngularUnit)
'Cast for the result.
Dim ipGCS As ESRI.ArcGIS.Geometry.IGeographicCoordinateSystem
ipGCS=ipGeoCSEdit

For further information see:

Using transformation objects

For further information see: