three.js/src/lights/SpotLight.js

import { Light } from './Light.js';
import { SpotLightShadow } from './SpotLightShadow.js';
import { Object3D } from '../core/Object3D.js';

function SpotLight( color, intensity, distance, angle, penumbra, decay ) {

	Light.call( this, color, intensity );

	this.type = 'SpotLight';

	this.position.copy( Object3D.DefaultUp );
	this.updateMatrix();

	this.target = new Object3D();

	Object.defineProperty( this, 'power', {
		get: function () {

			// intensity = power per solid angle.
			// ref: equation (17) from https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
			return this.intensity * Math.PI;

		},
		set: function ( power ) {

			// intensity = power per solid angle.
			// ref: equation (17) from https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
			this.intensity = power / Math.PI;

		}
	} );

	this.distance = ( distance !== undefined ) ? distance : 0;
	this.angle = ( angle !== undefined ) ? angle : Math.PI / 3;
	this.penumbra = ( penumbra !== undefined ) ? penumbra : 0;
	this.decay = ( decay !== undefined ) ? decay : 1;	// for physically correct lights, should be 2.

	this.shadow = new SpotLightShadow();

}

SpotLight.prototype = Object.assign( Object.create( Light.prototype ), {

	constructor: SpotLight,

	isSpotLight: true,

	copy: function ( source ) {

		Light.prototype.copy.call( this, source );

		this.distance = source.distance;
		this.angle = source.angle;
		this.penumbra = source.penumbra;
		this.decay = source.decay;

		this.target = source.target.clone();

		this.shadow = source.shadow.clone();

		return this;

	}

} );


export { SpotLight };