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assets/scripts/Preview.ts

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+// assets/scripts/Preview.ts
+import { _decorator, Component, Node, Prefab, instantiate, Vec3 } from "cc";
+import { BallPhysics } from "./BallPhysics";
+const { ccclass, property } = _decorator;
+
+@ccclass("Preview")
+export class Preview extends Component {
+  @property(Prefab) pointPrefab: Prefab = null!;
+  @property(Node) goal: Node = null!;
+
+  @property({ tooltip: "轨迹点数量" }) maxPoints = 30;
+  @property({ tooltip: "步长时间（秒）" }) timeStep = 0.05;
+
+  @property(BallPhysics) ballPhys: BallPhysics = null!;
+
+  private points: Node[] = [];
+
+  clear() {
+    for (const p of this.points) p.destroy();
+    this.points.length = 0;
+  }
+
+  /** 显示预测轨迹 */
+  showTrajectory(startPos: Vec3, dir: Vec3, speed: number, spin: Vec3) {
+    this.clear();
+    if (!this.pointPrefab || !this.ballPhys) return;
+
+    const goalZ = this.goal?.worldPosition?.z;
+
+    // 初始状态
+    let pos = startPos.clone();
+    let v = dir.clone().multiplyScalar(speed);
+    let w = spin.clone(); // 自旋
+
+    // 迭代预测
+    // let age = 0;
+    for (let i = 0; i < this.maxPoints; i++) {
+      // age += this.timeStep;
+      // 保存点
+      const p = instantiate(this.pointPrefab);
+      p.setWorldPosition(pos);
+      p.setParent(this.node);
+      this.points.push(p);
+
+      // === 模拟 BallPhysics.update(dt) ===
+      // const dt = this.timeStep;
+      const dt = this.timeStep * 0.5;
+
+      // 空气阻力
+      const speedNow = v.length();
+      if (speedNow > 0.01) {
+        const drag = v.clone().multiplyScalar(-this.ballPhys.dragK * speedNow);
+        v.add(drag.multiplyScalar(dt));
+      }
+
+      // 马格努斯效应：F = k * (ω × v)
+      if (w.lengthSqr() > 0.0001 && v.lengthSqr() > 0.0001) {
+        // const tFactor = 1.0 / (1.0 + age * 2.0); // age 是飞行时间，越久衰减越快
+        // const magnus = w
+        //   .clone()
+        //   .cross(v)
+        //   .multiplyScalar(this.ballPhys.magnusK * tFactor);
+        // v.add(magnus.multiplyScalar(dt));
+        const magnus = w.clone().cross(v).multiplyScalar(this.ballPhys.magnusK);
+        v.add(magnus.multiplyScalar(dt));
+      }
+
+      // 重力
+      v.y += -9.8 * dt;
+
+      // 移动
+      pos = pos.add(v.clone().multiplyScalar(dt));
+
+      if (
+        (startPos.z > goalZ && pos.z <= goalZ) ||
+        (startPos.z < goalZ && pos.z >= goalZ)
+      ) {
+        break;
+      }
+    }
+  }
+}