makeOBBFromRegion

Builds a conservative OrientedBoundingBox for a longitude–latitude–height region on an ellipsoid. This is useful for 3D Tiles regions, globe rendering, spatial indexing, and frustum culling.

The returned box is expressed in ellipsoid-fixed Cartesian coordinates. Its orientation is an implementation detail and may change between releases.

Usage

import {toRadians} from '@math.gl/core';
import {makeOBBFromRegion} from '@math.gl/geospatial';

const region = [
  toRadians(-30), // west
  toRadians(35),  // south
  toRadians(20),  // east
  toRadians(55),  // north
  0,              // minimumHeight
  1000            // maximumHeight
];

const box = makeOBBFromRegion(region);

Function

makeOBBFromRegion(region, ellipsoid?, options?) : OrientedBoundingBox

region is [west, south, east, north, minimumHeight, maximumHeight]. Longitudes and latitudes are in radians by default, matching the OGC 3D Tiles region definition. Heights use the ellipsoid's linear unit, normally meters. Use options.units: 'degrees' for degree input.

Latitudes must be in [-π/2, π/2] (or [-90, 90] in degree mode), south must not exceed north, and minimum height must not exceed maximum height.

Longitude wrapping

Longitude values outside the conventional range are accepted. The boundaries retain the directed eastward semantics used by 3D Tiles and LngLatRectangle: if east < west, the interval crosses the antimeridian and continues eastward through ±180°.

const datelineRegion = [170, -10, -170, 10, 0, 250];
const box = makeOBBFromRegion(datelineRegion, undefined, {units: 'degrees'});

This describes a 20° region centered on ±180°. A region from 10° to -10° is the directed 340° interval, not the shorter 20° interval. Equal endpoints describe zero width, while endpoints separated by one full turn (for example 0° to 360°) describe a full-globe longitude span.

Ellipsoid

The optional ellipsoid defaults to Ellipsoid.WGS84:

import {Ellipsoid, makeOBBFromRegion} from '@math.gl/geospatial';

const moon = new Ellipsoid(1737400, 1737400, 1737400);
const box = makeOBBFromRegion(region, moon);

Options

Property	Type	Default	Description
units	'radians' | 'degrees'	'radians'	Units for longitude and latitude. Heights are never converted.
transform	Matrix4	—	Affine transform from ellipsoid-fixed coordinates into world coordinates.

The transform is applied exactly once and may include translation, rotation, non-uniform scale, or shear. Translation affects the center; the linear part affects the half-axes. For 3D Tiles, do not automatically pass tile.transform: the 3D Tiles specification exempts region bounding volumes from that transform. Inputs and caller-owned values are never mutated.

Errors and edge cases

The function throws for malformed regions, non-finite values, reversed heights, or invalid latitudes. A tiny tolerance is allowed at the latitude boundaries and values are clamped to the exact pole before conversion.

Zero-width longitude, zero-height latitude, zero-height altitude, and point-like regions are valid. Regions touching either pole are valid and produce finite results even though longitude lines converge there. The box encloses the curved region conservatively; it is not an exact minimum-volume box.