Function geometry_predicates::predicates::orient3d

pub fn orient3d(pa: [f64; 3], pb: [f64; 3], pc: [f64; 3], pd: [f64; 3]) -> f64

Adaptive exact 3D orientation test. Robust.

Returns a positive value if the point pd lies below the plane passing through pa, pb, and pc; “below” is defined so that pa, pb, and pc appear in counterclockwise order when viewed from above the plane. Returns a negative value if pd lies above the plane. Returns zero if the points are coplanar. The result is also a rough approximation of six times the signed volume of the tetrahedron defined by the four points.

The result returned is the determinant of a matrix. This determinant is computed adaptively, in the sense that exact arithmetic is used only to the degree it is needed to ensure that the returned value has the correct sign. Hence, orient3d() is usually quite fast, but will run more slowly when the input points are coplanar or nearly so.