sphereInFrustum

function sphereInFrustum(frustum: FrustumPlanes, x: number, y: number, z: number, radius: number): boolean

import { sphereInFrustum } from '@driftengine/core';

Parameters

In depth

The question is "outside any one plane", not "inside every plane". A sphere is rejected only when it lies entirely on the far side of a single plane; anything else is kept. Asking whether the centre is inside all six is the version that looks equivalent and is not — it throws away everything larger than the view, so a room the camera is standing in vanishes.

Conservative at the corners: a sphere can be outside the frustum and still be within radius of all six planes, near an edge. That costs a draw that turns out to be invisible and never costs a draw that was visible, which is the only asymmetry a cull may have.