BoundingSphere

A bounding sphere with a center and a radius.

Usage

Create a bounding sphere around the unit cube

import {BoundingSphere} from '@math.gl/culling';
cont sphere = new BoundingSphere().fromCornerPoints(
  [-0.5, -0.5, -0.5],
  [0.5, 0.5, 0.5]
);

Sort bounding spheres from back to front

import {BoundingSphere} from '@math.gl/culling';
const spheres = [new BoundingSphere(...), new BoundingSphere(...), ...];
const cameraPosWC = ...;
spheres.sort(
  (a, b) => b.distanceSquaredTo(b, cameraPosWC) - a.distanceSquaredTo(a.cameraPosWC)
);

Global Functions

makeBoundingSphereFromPoints(positions : iterator, result? : BoundingSphere) : BoundingSphere

Computes a tight-fitting bounding sphere enclosing a list of 3D Cartesian points. The bounding sphere is computed by running two algorithms, a naive algorithm and Ritter's algorithm. The smaller of the two spheres is used to ensure a tight fit.

• positions An iterable (e.g. array) of points that the bounding sphere will enclose. Each point must have x, y, and z properties.
• result Optional object onto which to store the result.

Returns

• The modified result parameter or a new BoundingSphere instance if one was not provided.

See Bounding Sphere computation article

Fields

center : Vector3

The center point of the sphere.

radius : Number

The radius of the sphere.

Members

constructor(center : Number[3], radius : Number)

Creates a new BoundingSphere

• center=[0, 0, 0] The center of the bounding sphere.
• radius=0.0 The radius of the bounding sphere.

fromCenterRadius(center : Number[3], radius : Number) : BoundingSphere

Sets the BoundingSphere from center and radius

• center=[0, 0, 0] The center of the bounding sphere.
• radius=0.0 The radius of the bounding sphere.

fromCornerPoints(corner : Number[3], oppositeCorner : Number[3], result? : BoundingSphere) : BoundingSphere

Computes a bounding sphere from the two corner points of an axis-aligned bounding box. The sphere tighly and fully encompases the box.

• corner The minimum height over the rectangle.
• oppositeCorner The maximum height over the rectangle.

fromBoundingSpheres(boundingSpheres : BoundingSphere[]) : BoundingSphere

Computes a tight-fitting bounding sphere enclosing the provided array of bounding spheres.

• boundingSpheres The array of bounding spheres.

Returns

• The modified result parameter or a new BoundingSphere instance if none was provided.

clone()

Duplicates a BoundingSphere instance.

Returns

• A new BoundingSphere instance

equals(right : BoundingSphere) Boolean

Compares the provided BoundingSphere componentwise and returns true if they are equal, false otherwise.

• right The second BoundingSphere.

Returns

• true if left and right are equal, false otherwise.

union(right : BoundingSphere) : BoundingSphere

Computes a bounding sphere that contains both the this and the right bounding spheres.

• right The second BoundingSphere.

expand(point : Number[3]) : BoundingSphere

Computes a bounding sphere by enlarging the provided sphere to contain the provided point.

• point A point to enclose in a bounding sphere.

intersectPlane(plane : Plane) : INTERSECTION

Determines which side of a plane a sphere is located.

• plane The plane to test against. Returns
• INTERSECTION.INSIDE if the entire sphere is on the side of the plane the normal is pointing
• INTERSECTION.OUTSIDE if the entire sphere is on the opposite side
• INTERSECTION.INTERSECTING if the sphere intersects the plane.

transform(transform : Number[16]) : BoundingSphere

Applies a 4x4 affine transformation matrix to a bounding sphere.

• transform The transformation matrix to apply to the bounding sphere.

distanceSquaredTo(point) : Number

Computes the estimated distance squared from the closest point on a bounding sphere to a point.

• point The point

Returns

• The estimated distance squared from the bounding sphere to the point.

transformWithoutScale(sphere, transform, result)

Applies a 4x4 affine transformation matrix to a bounding sphere where there is no scale The transformation matrix is not verified to have a uniform scale of 1. This method is faster than computing the general bounding sphere transform using {@link BoundingSphere.transform}.

@param {BoundingSphere} sphere The bounding sphere to apply the transformation to. @param {Matrix4} transform The transformation matrix to apply to the bounding sphere.

• result Optional object onto which to store the result.

Returns

• The modified result parameter or a new BoundingSphere instance if none was provided.

@example var modelMatrix = Transforms.eastNorthUpToFixedFrame(positionOnEllipsoid); var boundingSphere = new BoundingSphere(); var newBoundingSphere = BoundingSphere.transformWithoutScale(boundingSphere, modelMatrix);

computePlaneDistances (sphere, position, direction, result)

The distances calculated by the vector from the center of the bounding sphere to position projected onto direction plus/minus the radius of the bounding sphere.

If you imagine the infinite number of planes with normal direction, this computes the smallest distance to the closest and farthest planes from position that intersect the bounding sphere.

@param {BoundingSphere} sphere The bounding sphere to calculate the distance to. @param {Cartesian3} position The position to calculate the distance from. @param {Cartesian3} direction The direction from position. @param {Interval} [result] A Interval to store the nearest and farthest distances. @returns {Interval} The nearest and farthest distances on the bounding sphere from position in direction.

projectTo2D(sphere, projection, result)

Creates a bounding sphere in 2D from a bounding sphere in 3D world coordinates.

@param {BoundingSphere} sphere The bounding sphere to transform to 2D. @param {Object} [projection=GeographicProjection] The projection to 2D.

• result Optional object onto which to store the result.

Returns

• The modified result parameter or a new BoundingSphere instance if none was provided.

Attribution

This class was ported from Cesium under the Apache 2 License.