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Assets/Scripts/Test/BobberBuoyancyStable.cs

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+using UnityEngine;
+
+[DisallowMultipleComponent]
+[RequireComponent(typeof(Rigidbody))]
+[RequireComponent(typeof(CapsuleCollider))]
+public class BobberBuoyancyStable : MonoBehaviour
+{
+    [Header("Water")]
+    public float waterLevelY = 0f;
+
+    [Tooltip("必须至少浸入这么深才开始产生浮力（防止还没入水就被顶）")]
+    public float enterWaterDepth = 0.003f; // 3mm（按你的尺度改）
+
+    [Tooltip("在这个深度范围内做平滑过渡（越大越软）")]
+    public float smoothDepth = 0.02f;
+
+    [Header("Buoyancy Spring")]
+    public float buoyancySpring = 30f;
+    public float buoyancyDamping = 8f;
+
+    [Tooltip("最大上浮加速度限制(0=不限制)")]
+    public float maxUpAcceleration = 0f;
+
+    [Header("Water Drag")]
+    public float extraLinearDampingInWater = 2f;
+    public float extraAngularDampingInWater = 2f;
+
+    [Header("Center Of Mass")]
+    public bool driveCenterOfMassFromCapsule = true;
+    public Vector3 extraCenterOfMassOffset = new Vector3(0f, -0.01f, 0f);
+
+    [Header("Righting")]
+    public float rightingTorque = 1.5f;
+    public float rightingDamping = 0.5f;
+
+    Rigidbody rb;
+    CapsuleCollider cap;
+
+    float airLinearDamping;
+    float airAngularDamping;
+
+    void Awake()
+    {
+        rb = GetComponent<Rigidbody>();
+        cap = GetComponent<CapsuleCollider>();
+        rb.useGravity = true;
+
+        airLinearDamping = rb.linearDamping;
+        airAngularDamping = rb.angularDamping;
+
+        ApplyCenterOfMass();
+        rb.maxAngularVelocity = 50f;
+    }
+
+    void FixedUpdate()
+    {
+        ApplyCenterOfMass();
+
+        Bounds b = cap.bounds;
+        float bottomY = b.min.y;
+        float topY = b.max.y;
+
+        // 用“底部点”判定是否真正入水（必须超过阈值）
+        float bottomSubmersion = waterLevelY - bottomY; // >0 表示底部在水下
+        if (bottomSubmersion <= enterWaterDepth)
+        {
+            // 认为未入水：不施加浮力，恢复空气阻尼
+            rb.linearDamping = airLinearDamping;
+            rb.angularDamping = airAngularDamping;
+            return;
+        }
+
+        // 进入水中：阻尼随浸入增强
+        // 这里用一个0~1的平滑权重，避免刚入水就“猛顶”
+        float w = Smooth01((bottomSubmersion - enterWaterDepth) / Mathf.Max(1e-4f, smoothDepth));
+
+        rb.linearDamping = airLinearDamping + extraLinearDampingInWater * w;
+        rb.angularDamping = airAngularDamping + extraAngularDampingInWater * w;
+
+        // 垂直速度（用刚体自身速度就够稳定）
+        float vY = rb.linearVelocity.y;
+
+        // 弹簧+阻尼浮力（仅向上）
+        float forceY = buoyancySpring * bottomSubmersion - buoyancyDamping * vY;
+        if (forceY < 0f) forceY = 0f;
+
+        // 平滑权重：刚入水时逐渐接管
+        forceY *= w;
+
+        // 限制最大上浮加速度（可选）
+        if (maxUpAcceleration > 0f)
+        {
+            float maxForce = rb.mass * maxUpAcceleration;
+            if (forceY > maxForce) forceY = maxForce;
+        }
+
+        // 浮力作用点：必须放在水面下（否则会出现奇怪力矩）
+        float buoyY = Mathf.Min(waterLevelY - 0.001f, topY); // 强制在水面下1mm
+        buoyY = Mathf.Max(buoyY, bottomY);                  // 不低于底部
+        Vector3 buoyPoint = new Vector3(b.center.x, buoyY, b.center.z);
+
+        rb.AddForceAtPosition(Vector3.up * forceY, buoyPoint, ForceMode.Force);
+
+        // 归正扭矩（只在水里生效）
+        Vector3 up = transform.up;
+        Vector3 axis = Vector3.Cross(up, Vector3.up);
+        float mag = axis.magnitude;
+        if (mag > 1e-4f)
+        {
+            axis /= mag;
+            float angle = Mathf.Asin(Mathf.Clamp(mag, -1f, 1f));
+            float angVelOnAxis = Vector3.Dot(rb.angularVelocity, axis);
+            float torque = (rightingTorque * angle - rightingDamping * angVelOnAxis) * w;
+            rb.AddTorque(axis * torque, ForceMode.Acceleration);
+        }
+    }
+
+    void ApplyCenterOfMass()
+    {
+        if (!driveCenterOfMassFromCapsule) return;
+        rb.centerOfMass = cap.center + extraCenterOfMassOffset;
+    }
+
+    static float Smooth01(float t)
+    {
+        t = Mathf.Clamp01(t);
+        // smoothstep
+        return t * t * (3f - 2f * t);
+    }
+}