Unity实现布料效果（软体效果）

原理

很好奇糖豆人这种软体效果是怎么实现的，于是查看了一些资料了解到可以通过改变mesh来使物体产生不一样的渲染效果。
主要通过类似弹簧的效果，点击物体后改变该物体的vertices，某个点离施力点越近则给它的初速度越大。初速度根据该点移动的距离慢慢减小，当减小为0后再次反弹至原点。

实现

外部接口为AddForce函数

using UnityEngine;
public class softBodyTest : MonoBehaviour {Mesh mesh;Vector3[] originalVertices;//原来的点Vector3[] displacedVertices;//改变后的点Vector3[] vertexVelocities;//每个点的当前速度[Header("弹簧力")]public float springForce = 20f;[Header("弹簧阻尼")]public float damping = 5;// Use this for initializationvoid Start() {mesh = GetComponent<MeshFilter>().mesh;originalVertices = mesh.vertices;displacedVertices = new Vector3[originalVertices.Length];for (int i = 0; i < displacedVertices.Length; i++){displacedVertices[i] = originalVertices[i];}vertexVelocities = new Vector3[originalVertices.Length];}void Update () {for (int i = 0; i < displacedVertices.Length; i++){var velocity = vertexVelocities[i];Vector3 displacement = displacedVertices[i] - originalVertices[i];velocity -= displacement * springForce * Time.deltaTime;//减小的加速度与弹簧力有关 该点与原点的距离相当于弹簧的压缩量velocity *= 1f - damping * Time.deltaTime;//防止弹簧反复横跳，增加阻尼vertexVelocities[i] = velocity;displacedVertices[i] += velocity * Time.deltaTime;}mesh.vertices = displacedVertices;mesh.RecalculateNormals();}public void AddForce(Vector3 point, Vector3 direction, float force){Debug.DrawLine(Camera.main.transform.position, point);point = transform.InverseTransformPoint(point);for (int i = 0; i < displacedVertices.Length; i++){AddForceToVertex(i, point, direction, force);}}private void AddForceToVertex(int i, Vector3 point,Vector3 direction, float force){var pointToVertex = displacedVertices[i] - point;float attenuateForce = force / (0.1f + pointToVertex.sqrMagnitude); //距离越近力越大float velocity = attenuateForce * Time.deltaTime;vertexVelocities[i] -= direction.normalized * velocity; //初速度}
}

测试代码

if (Input.GetMouseButton(0)){Ray inputRay = Camera.main.ScreenPointToRay(Input.mousePosition);RaycastHit hit;if (Physics.Raycast(inputRay, out hit)){var testScript = hit.collider.GetComponent<softBodyTest>();if (testScript){var point = hit.point;testScript.AddForce(point, hit.normal, force);}}}

最终效果