SphereEmitter.ts

import {EmitterMode, EmitterShape, getValueFromEmitterMode, ShapeJSON} from './EmitterUtil';
import {Particle} from '../Particle';
import {MathUtils, Matrix3, Matrix4, Quaternion, Vector3} from '../math';
import {
    ConstantValue,
    FunctionValueGenerator,
    GeneratorMemory,
    ValueGenerator,
    ValueGeneratorFromJSON,
} from '../functions';
import {EmissionState, IParticleSystem} from '../IParticleSystem';
import { UP_VEC3, ZERO_VEC3 } from '../util/MathUtil';

/**
 * Interface representing the parameters for a sphere emitter.
 */
export interface SphereEmitterParameters {
    /**
     * The radius of the sphere.
     */
    radius?: number;
    /**
     * The arc of the sphere.
     */
    arc?: number;
    /**
     * The thickness of the sphere. 1 is a full sphere, 0 is a thin shell.
     */
    thickness?: number;
    /**
     * The mode of the emitter.
     * {@link EmitterMode}
     */
    mode?: EmitterMode;
    /**
     * The length of the segment at which the emitter point converges at the start and end, when mode is EmitterMode.Loop or EmitterMode.PingPong.
     * {@link EmitterMode}
     */
    spread?: number;
    /**
     * The speed of the emitter start point when mode is EmitterMode.Loop or EmitterMode.PingPong.
     * {@link EmitterMode}
     */
    speed?: ValueGenerator | FunctionValueGenerator;
}

export class SphereEmitter implements EmitterShape {
    type = 'sphere';
    radius: number;
    arc: number;
    thickness: number; //[0, 1]
    mode: EmitterMode;
    spread: number;
    speed: ValueGenerator | FunctionValueGenerator;
    memory: GeneratorMemory;

    _m1: Matrix4;

    constructor(parameters: SphereEmitterParameters = {}) {
        this.radius = parameters.radius ?? 10;
        this.arc = parameters.arc ?? 2.0 * Math.PI;
        this.thickness = parameters.thickness ?? 1;
        this.mode = parameters.mode ?? EmitterMode.Random;
        this.spread = parameters.spread ?? 0;
        this.speed = parameters.speed ?? new ConstantValue(1);
        this.memory = [];

        this._m1 = new Matrix4();
    }

    private currentValue = 0;

    update(system: IParticleSystem, delta: number): void {
        if (EmitterMode.Random != this.mode) {
            this.currentValue += this.speed.genValue(this.memory, system.emissionState.time / system.duration) * delta;
        }
    }

    initialize(p: Particle, emissionState: EmissionState) {
        const u = getValueFromEmitterMode(this.mode, this.currentValue, this.spread, emissionState);
        const v = Math.random();
        const rand = MathUtils.lerp(1 - this.thickness, 1, Math.random());
        const theta = u * this.arc;
        const phi = Math.acos(2.0 * v - 1.0);
        const sinTheta = Math.sin(theta);
        const cosTheta = Math.cos(theta);
        const sinPhi = Math.sin(phi);
        const cosPhi = Math.cos(phi);
        p.position.x = sinPhi * cosTheta;
        p.position.y = sinPhi * sinTheta;
        p.position.z = cosPhi;

        p.velocity.copy(p.position).multiplyScalar(p.startSpeed);
        p.position.multiplyScalar(this.radius * rand);

        if (p.rotation instanceof Quaternion) {
            this._m1.lookAt(ZERO_VEC3, p.position, UP_VEC3);
            p.rotation.setFromRotationMatrix(this._m1);
        }
    }

    toJSON(): ShapeJSON {
        return {
            type: 'sphere',
            radius: this.radius,
            arc: this.arc,
            thickness: this.thickness,
            mode: this.mode,
            spread: this.spread,
            speed: this.speed.toJSON(),
        };
    }

    static fromJSON(json: any): SphereEmitter {
        return new SphereEmitter({
            radius: json.radius,
            arc: json.arc,
            thickness: json.thickness,
            mode: json.mode,
            speed: json.speed ? ValueGeneratorFromJSON(json.speed) : undefined,
            spread: json.spread,
        });
    }

    clone(): EmitterShape {
        return new SphereEmitter({
            radius: this.radius,
            arc: this.arc,
            thickness: this.thickness,
            mode: this.mode,
            speed: this.speed.clone(),
            spread: this.spread,
        });
    }
}