CurveToLineWithTolerance (geometry Data Type)
Returns a polygonal approximation of a geometry instance that contains circular arc segments.
Syntax
.CurveToLineWithTolerance ( tolerance, relative )
Arguments
tolerance
Is a double expression that defines the maximum error between the original circular arc segment and its linear approximation.relative
Is a bool expression that indicates whether to use a relative maximum for the deviation. When relative is set to false (0), then an absolute maximum is set for the deviation that a linear approximate can have. When relative is set to true (1) then the tolerance is calculated as a product of the tolerance parameter and the diameter of the bounding box for the spatial object.
Return Types
SQL Server return type: geometry
CLR return type: SqlGeometry
Exceptions
Setting tolerance <= 0 throws an ArgumentOutOfRange exception.
Remarks
This method can specify an error tolerance amount for the resultant LineString.
The following table shows the instance type returned by CurveToLineWithTolerance()for various types.
Invoking Instance Type |
Spatial Type Returned |
|---|---|
Empty geometry instance |
Empty GeometryCollection instance |
Point and MultiPoint |
Point instance |
MultiPoint |
Point or MultiPoint instance |
CircularString, CompoundCurve, or LineString |
LineString instance |
MultiLineString |
LineString or MultiLineString instance |
CurvePolygon and Polygon |
Polygon instance |
MultiPolygon |
Polygon or MultiPolygon instance |
GeometryCollection with a single instance that does not contain a circular arc segment |
The instance that is contained in the GeometryCollection determines the type of instance returned. |
GeometryCollection with a single one-dimensional circular arc segment instance (CircularString, CompoundCurve) |
LineString instance |
GeometryCollection with a single two-dimensional circular arc segment instance (CurvePolygon) |
Polygon instance |
GeometryCollection with multiple one dimensional instances |
MultiLineString instance |
GeometryCollection with multiple two dimensional instances |
MultiPolygon instance |
GeometryCollection with multiple instances of different dimensions |
GeometryCollection instance |
Examples
A. Using different tolerance values on a CircularString instance
The following example shows how setting the tolerance affects the LineString instance returned from a CircularString instance:
DECLARE @g geometry;
SET @g = geometry::Parse('CIRCULARSTRING(0 0, 1 2.1082, 3 6.3246, 0 7, -3 6.3246, -1 2.1082, 0 0)');
SELECT @g.CurveToLineWithTolerance(0.1,0).STNumPoints(), @g.CurveToLineWithTolerance(0.01, 0).STNumPoints();
B. Using the method on a MultiLineString instance containing one LineString
The following example shows what is returned from a MultiLineString instance that only contains one LineString instance:
DECLARE @g geometry;
SET @g = geometry::Parse('MULTILINESTRING((1 3, 4 8, 6 9))');
SELECT @g.CurveToLineWithTolerance(0.1,0).ToString();
C. Using the method on a MultiLineString instance containing multiple LineStrings
The following example shows what is returned from a MultiLineString instance that contains more than one LineString instance:
DECLARE @g geometry;
SET @g = geometry::Parse('MULTILINESTRING((1 3, 4 8, 6 9),(4 4, 9 18))');
SELECT @g.CurveToLineWithTolerance(0.1,0).ToString();
D. Setting relative to true for an invoking CurvePolygon instance
The following example uses a CurvePolygon instance to call CurveToLineWithTolerance() with relative set to true:
DECLARE @g geometry = 'CURVEPOLYGON(COMPOUNDCURVE(CIRCULARSTRING(0 4, 4 0, 8 4), (8 4, 0 4)))';
SELECT @g.CurveToLineWithTolerance(.5,1).ToString();
E. Using the method on a GeometryCollection instance
The following example calls CurveToLineWithTolerance() on a GeometryCollection that contains a two-dimensional CurvePolygon instance and a one-dimensional CircularString instance. CurveToLineWithTolerance() converts both circular arc segment types to line segment types and returns them in a GeometryCollection type.
DECLARE @g geometry;
SET @g = geometry::Parse('GEOMETRYCOLLECTION(CURVEPOLYGON( COMPOUNDCURVE(CIRCULARSTRING(0 2, 2 0, 4 2), (4 2, 0 2))), CIRCULARSTRING(4 4, 8 6, 9 5))');
SELECT @g.CurveToLineWithTolerance(0.1,0).STNumPoints(), @g.CurveToLineWithTolerance(0.1, 0).ToString();