## Name

ST_ChaikinSmoothing — Returns a smoothed version of a geometry, using the Chaikin algorithm

## Synopsis

`geometry `**ST_ChaikinSmoothing**(

geometry `geom`, integer `nIterations = 1`, boolean `preserveEndPoints = false``)`

;

## Beschreibung

Smoothes a linear or polygonal geometry using Chaikin's algorithm. The degree of smoothing is controlled by the `nIterations`

parameter. On each iteration, each interior vertex is replaced by two vertices located at 1/4 of the length of the line segments before and after the vertex. A reasonable degree of smoothing is provided by 3 iterations; the maximum is limited to 5.

If `preserveEndPoints`

is true, the endpoints of Polygon rings are not smoothed. The endpoints of LineStrings are always preserved.

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The number of vertices doubles with each iteration, so the result geometry may have many more points than the input. To reduce the number of points use a simplification function on the result (see ST_Simplify, ST_SimplifyPreserveTopology and ST_SimplifyVW). |

The result has interpolated values for the Z and M dimenions when present.

This function supports 3d and will not drop the z-index.

Verfügbarkeit: 2.5.0

## Beispiele

Smoothing a triangle:

SELECT ST_AsText(ST_ChaikinSmoothing(geom)) smoothed
FROM (SELECT 'POLYGON((0 0, 8 8, 0 16, 0 0))'::geometry geom) AS foo;
smoothed
───────────────────────────────────────────
POLYGON((2 2,6 6,6 10,2 14,0 12,0 4,2 2))

Smoothing a Polygon using 1, 2 and 3 iterations:

SELECT ST_ChaikinSmoothing(
'POLYGON ((20 20, 60 90, 10 150, 100 190, 190 160, 130 120, 190 50, 140 70, 120 10, 90 60, 20 20))',
generate_series(1, 3) );

Smoothing a LineString using 1, 2 and 3 iterations:

SELECT ST_ChaikinSmoothing(
'LINESTRING (10 140, 80 130, 100 190, 190 150, 140 20, 120 120, 50 30, 30 100)',
generate_series(1, 3) );