Use ST_RayIntersection to calculate intersections of sfmesh objects and rays - PolarDB

Calculates the intersections between an sfmesh object and a set of rays that share the same direction vector.

Syntax

geometry ST_RayIntersection(sfmesh sfmesh, geometry mpoint, geometry direction);

Return value

Returns a MULTIPOINT geometry representing the intersections of sfmesh objects and rays. Returns EMPTY if no intersection exists.

Parameters

Parameter	Type	Description
`sfmesh`	sfmesh	The sfmesh model object.
`mpoint`	MULTIPOINT	The endpoint of the ray.
`direction`	POINT	The direction of the ray.

Usage notes

All rays in a single call share the same direction. To calculate intersections for rays with different directions, call ST_RayIntersection once per direction.
direction is a direction vector, not a target position. Each ray starts from a point in mpoint and extends along this vector.

Examples

The following example calculates intersections for four rays. Each ray starts from one of the four points in mpoint and travels in the +Y direction. The sfmesh is a flat polygon on the Z=0 plane.

SELECT ST_AsText(ST_RayIntersection(
    'POLYGON((-1 -1 0, 1 -1 0, 1 1 0, -1 1 0, -1 -1 0))'::geometry::meshgeom,
    'MULTIPOINT(0 0 0, 0 1 0, 0 -1 0, 0 -2 0)'::geometry,
    'POINT(0 1 0)'::geometry
));

Output:

MULTIPOINT Z ((0 0 0),(0 1 0),(0 -1 0),(0 -1 0))