FrustumArray: Optimize frustum computations.

[Mugen87]

Related issue: #33797

Description

It turned out FrustumArray computes the frustum for each intersection test over and over again which is quite inefficient. The PR introduces a new method setFromArrayCamera() that allows to compute the frustums once for later intersection tests.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	365.59 86.85	365.59 86.85	+0 B +0 B
WebGPU	667.09 184.91	667.13 184.92	+42 B +8 B
WebGPU Nodes	665.13 184.61	665.17 184.62	+42 B +11 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	507.7 123.42	507.7 123.42	+0 B +0 B
WebGPU	747.08 201.29	746.74 201.34	-346 B +57 B
WebGPU Nodes	697.4 188.92	697.05 188.94	-346 B +21 B

[RenaudRohlinger]

Nice optimization overall.

Could we preserve the cached state in clone() here? Right now an initialized FrustumArray clones to an empty one, so intersection checks on the clone return false until setFromArrayCamera() is called again.

One option would be to add the usual copy() helper and have clone() delegate to it:

/**
 * Copies the values of the given frustum array to this instance.
 *
 * @param {FrustumArray} source - The frustum array to copy.
 * @return {FrustumArray} A reference to this frustum array.
 */
copy( source ) {

	this.coordinateSystem = source.coordinateSystem;
	this._count = source._count;

	for ( let i = 0; i < source._count; i ++ ) {

		if ( this._frustums[ i ] === undefined ) this._frustums[ i ] = new Frustum();

		this._frustums[ i ].copy( source._frustums[ i ] );

	}

	this._frustums.length = source._count;

	return this;

}


clone() {

	return new this.constructor().copy( this );

}

[Mugen87]

Good point! I've added copy() and use it in clone() now.