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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)
);

Inheritance​

class BoundingSphere implements BoundingVolume.

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
  • 'inside' if the entire sphere is on the side of the plane the normal is pointing
  • 'outside' if the entire sphere is on the opposite side
  • '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 BoundingSphere.transform.

  • BoundingSphere sphere The bounding sphere to apply the transformation to.

  • 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.

  • BoundingSphere sphere The bounding sphere to calculate the distance to.
  • Cartesian3 position The position to calculate the distance from.
  • Cartesian3 direction The direction from position.
  • 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.

  • BoundingSphere sphere The bounding sphere to transform to 2D.

  • 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.