tanqiu/assets/scripts/Animations/PelletTrailController.ts

import { _decorator, Component, Node, ParticleSystem2D, Vec2, RigidBody2D } from 'cc';
const { ccclass, property } = _decorator;

/**
 * 子弹尾迹控制器
 * 控制子弹的粒子系统尾迹效果
 */
@ccclass('PelletTrailController')
export class PelletTrailController extends Component {
    @property(ParticleSystem2D)
    particleSystem: ParticleSystem2D = null;
    
    @property(RigidBody2D)
    rigidBody: RigidBody2D = null;
    
    private lastVelocity: Vec2 = new Vec2();
    
    onLoad() {
        // 自动获取组件引用
        if (!this.particleSystem) {
            this.particleSystem = this.node.getComponentInChildren(ParticleSystem2D);
        }
        if (!this.rigidBody) {
            this.rigidBody = this.node.getComponent(RigidBody2D);
        }
    }
    
    start() {
        // 启动粒子系统
        if (this.particleSystem) {
            this.particleSystem.resetSystem();
        }
    }
    
    update(deltaTime: number) {
        if (!this.particleSystem || !this.rigidBody) return;
        
        // 获取当前速度
        const velocity = this.rigidBody.linearVelocity;
        
        // 如果速度发生变化，更新粒子发射角度
        if (!velocity.equals(this.lastVelocity)) {
            this.updateParticleDirection(velocity);
            this.lastVelocity.set(velocity);
        }
        
        // 根据速度调整粒子发射率
        const speed = velocity.length();
        if (speed > 0) {
            // 速度越快，尾迹越明显
            this.particleSystem.emissionRate = Math.max(20, speed * 0.5);
            this.particleSystem.enabled = true;
        } else {
            // 静止时停止发射粒子
            this.particleSystem.enabled = false;
        }
    }
    
    /**
     * 根据子弹移动方向更新粒子发射方向
     * @param velocity 子弹速度向量
     */
    private updateParticleDirection(velocity: Vec2) {
        if (velocity.length() === 0) return;
        
        // 计算速度方向角度（弧度转角度）
        const angle = Math.atan2(velocity.y, velocity.x) * 180 / Math.PI;
        
        // 粒子向相反方向发射，形成尾迹效果
        this.particleSystem.angle = angle + 180;
        
        // 根据速度调整粒子初始速度
        const speed = velocity.length();
        this.particleSystem.speed = Math.min(100, speed * 0.8);
        this.particleSystem.speedVar = Math.min(30, speed * 0.2);
    }
    
    /**
     * 设置尾迹颜色
     * @param color 颜色值 (0-255)
     */
    public setTrailColor(r: number, g: number, b: number, a: number = 255) {
        if (!this.particleSystem) return;
        
        this.particleSystem.startColor.set(r, g, b, a);
        // 结束颜色保持透明
        this.particleSystem.endColor.set(r, g, b, 0);
    }
    
    /**
     * 启用/禁用尾迹效果
     */
    public setTrailEnabled(enabled: boolean) {
        if (this.particleSystem) {
            this.particleSystem.enabled = enabled;
            if (enabled) {
                this.particleSystem.resetSystem();
            }
        }
    }
}