Version: 2022.2
LanguageEnglish
  • C#

Physics.ContactEvent

Suggest a change

Success!

Thank you for helping us improve the quality of Unity Documentation. Although we cannot accept all submissions, we do read each suggested change from our users and will make updates where applicable.

Close

Submission failed

For some reason your suggested change could not be submitted. Please <a>try again</a> in a few minutes. And thank you for taking the time to help us improve the quality of Unity Documentation.

Close

Cancel

Parameters

value A delegate to call.

Description

Subscribe to this event to read all collisions that occurred during the physics simulation step.

Each subscriber to this event gets invoked with a physics scene and a native array of ContactPairHeaders. Each ContactPairHeader contains an array of ContactPairs and each ContactPair contains an array of ContactPairPoints.

This event can be used to speed up the contact processing as it is a lot faster than MonoBehaviour.OnCollisionEnter and other messages. This event can be used to schedule jobs that use the provided native array. Jobs that are scheduled from this event must be completed before the next Physics.Simulate or PhysicsScene.Simulate call. By default a good place for completing these jobs is MonoBehaviour.FixedUpdate.

Notes:

  • Only Collider collisions are reported in this event and no trigger events will appear in the provided buffer.
  • All the data in the provided buffer is read-only. No writes are permited.
  • The event is invoked after the transform sync.
  • To receive contacts from a Collider, set the Collider.providesContacts property to true or attach a MonoBehaviour script with an OnCollisionStay method.
using System.Collections.Generic;
using Unity.Collections;
using Unity.Jobs;
using UnityEngine;

public class BounceScipt : MonoBehaviour { [SerializeField] private float m_ImpulseMultiplier = 5f;

private struct JobResultStruct { public int thisInstanceID; public int otherInstanceID; public Vector3 averageNormal; }

private NativeArray<JobResultStruct> m_ResultsArray; private int m_Count; private JobHandle m_JobHandle;

private readonly Dictionary<int, Rigidbody> m_RigidbodyMapping = new Dictionary<int, Rigidbody>();

private void OnEnable() { m_ResultsArray = new NativeArray<JobResultStruct>(16, Allocator.Persistent);

Physics.ContactEvent += Physics_ContactEvent;

var allRBs = GameObject.FindObjectsOfType<Rigidbody>(); foreach (var rb in allRBs) m_RigidbodyMapping.Add(rb.GetInstanceID(), rb); }

private void OnDisable() { m_JobHandle.Complete(); m_ResultsArray.Dispose();

Physics.ContactEvent -= Physics_ContactEvent;

m_RigidbodyMapping.Clear(); }

private void FixedUpdate() { m_JobHandle.Complete(); // The buffer is valid until the next Physics.Simulate() call. Be it internal or manual

// Do something with the contact data. // E.g. Add force based on the average contact normal for that body for (int i = 0; i < m_Count; i++) { var thisInstanceID = m_ResultsArray[i].thisInstanceID; var otherInstanceID = m_ResultsArray[i].otherInstanceID;

var rb0 = thisInstanceID != 0 ? m_RigidbodyMapping[thisInstanceID] : null; var rb1 = otherInstanceID != 0 ? m_RigidbodyMapping[otherInstanceID] : null;

if (rb0) rb0.AddForce(m_ResultsArray[i].averageNormal * m_ImpulseMultiplier, ForceMode.Impulse); if (rb1) rb1.AddForce(m_ResultsArray[i].averageNormal * -m_ImpulseMultiplier, ForceMode.Impulse); } }

private void Physics_ContactEvent(PhysicsScene scene, NativeArray<ContactPairHeader>.ReadOnly pairHeaders) { int n = pairHeaders.Length;

if (m_ResultsArray.Length < n) { m_ResultsArray.Dispose(); m_ResultsArray = new NativeArray<JobResultStruct>(Mathf.NextPowerOfTwo(n), Allocator.Persistent); }

m_Count = n;

AddForceJob job = new AddForceJob() { pairHeaders = pairHeaders, resultsArray = m_ResultsArray };

m_JobHandle = job.Schedule(n, 256); }

private struct AddForceJob : IJobParallelFor { [ReadOnly] public NativeArray<ContactPairHeader>.ReadOnly pairHeaders;

public NativeArray<JobResultStruct> resultsArray;

public void Execute(int index) { Vector3 averageNormal = Vector3.zero; int count = 0;

for (int j = 0; j < pairHeaders[index].pairCount; j++) { ref readonly var pair = ref pairHeaders[index].GetContactPair(j);

if (pair.IsCollisionExit) continue;

for (int k = 0; k < pair.ContactCount; k++) { ref readonly var contact = ref pair.GetContactPoint(k); averageNormal += contact.Normal; }

count += pair.ContactCount; }

if (count != 0) averageNormal /= (float)count;

JobResultStruct result = new JobResultStruct() { thisInstanceID = pairHeaders[index].bodyInstanceID, otherInstanceID = pairHeaders[index].otherBodyInstanceID, averageNormal = averageNormal };

resultsArray[index] = result; } } }

This script reads all the contacts in the buffer and computes the average normal for each ContactPairHeader. Then applies a force based on the result.

Copyright © 2023 Unity Technologies
优美缔软件(上海)有限公司 版权所有
"Unity"、Unity 徽标及其他 Unity 商标是 Unity Technologies 或其附属机构在美国及其他地区的商标或注册商标。其他名称或品牌是其各自所有者的商标。
公安部备案号:
31010902002961