main/src/georegression/metric/Distance3D_F64.java
public static double distance( Sphere3D_F64 sphere , Point3D_F64 point ) {

		double r = point.distance(sphere.center);
		return r-sphere.radius;
	}
public static double distance( Sphere3D_F64 sphere , Point3D_F64 point ) {

		double r = point.distance(sphere.center);
		return r-sphere.radius;
	}
Returns the signed distance a point is from the sphere's surface.  If the point is outside of the sphere
it's distance will be positive.  If it is inside it will be negative.
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distance = ||sphere.center - point|| - r

@param sphere The sphere
@param point The point
@return Signed distance