ST_SnapToPolygon for smoothly fitting sfmesh vertices to 3D polygons - PolarDB

Smoothly fits terrain mesh (sfmesh) vertices to a 3D polygon along the Z axis.

Syntax

sfmesh ST_SnapToPolygon(sfmesh sfmesh, geometry geom, f8 zlowd, f8 zupd, f8 buffer, i4 times);

Return value

Returns the sfmesh object with its vertices smoothly fit to the target polygon.

Parameters

Parameter	Type	Description
`sfmesh`	sfmesh	The sfmesh model object whose vertices are fit to the polygon.
`geom`	geometry	The target 3D polygon.
`zlowd`	f8	The lower Z distance limit. Only vertices within the Z range defined by `zlowd` and `zupd` are fit.
`zupd`	f8	The upper Z distance limit. Only vertices within the Z range defined by `zlowd` and `zupd` are fit.
`buffer`	f8	The buffer used for smooth fitting.
`times`	i4	The number of fitting iterations. More iterations produce a smoother result. Set a value between 5 and 20.

Usage notes

zlowd and zupd specify the vertices to be smoothly fit.
buffer sets the smooth transition range.
times defines the number of smooth fitting actions. A higher number of smooth fitting actions brings a better fitting result.

Example

The following example intersects a sphere with a bounding box to produce an sfmesh, then snaps its vertices to a thin polygon strip along the Y axis with times set to 10.

SELECT BOX3D(ST_SnapToPolygon(
    ST_3DIntersection(ST_3DMakeSphere(1.0, 4), 'BOX3D(-1 -1 0, 1 1 1)'::box3d),
    'POLYGON((-5 -0.1 0.5, 5 -0.1 0.5, 5 0.1 0.5, -5 0.1 0.5, -5 -0.1 0.5))', 0.5, 0.5, 0.5, 10));

Result:

BOX3D(-1 -1 0,1 1 0.782785594463348)