碰撞接触处理

To create sparks, we are going to use the VFX add-on (you can download it on https://store.unigine.com).要创建火花，我们将使用 VFX附加组件(您可以在 https://store.unigine.com 网站上下载)。

Create a new project in UNIGINE SDK Browser and import the VFX add-on to it.在UNIGINE SDK浏览器中创建一个新项目并导入VFX插件。

Open the project in the UnigineEditor and add some primitive objects to the default scene.在UnigineEditor中打开项目，并在默认场景中添加一些基本对象。

Let's get some information about the contacts the blue box will have with other objects.让我们获取一些关于蓝框与其他物体的接触的信息。

On collision, contacts are distributed randomly between the interacting bodies to optimize performance: some are handled by the first body, others by the second. For a body, contacts that it handles itself are internal (access to them is fast), and contacts handled by other bodies are external.在碰撞时，接触在相互作用的物体之间随机分布以优化性能:一些物体由第一个物体处理，另一些由第二个物体处理。对于一个体来说，它自己处理的接触是 internal(访问它们是快速的)，其他体处理的接触是external。

注意

You can iterate through all contacts for a body, but for better performance it is recommended to process only internal ones.您可以遍历物体的所有接触，但为了获得更好的性能，建议只处理内部接触。

The box is a high-priority body for us and we want to track its collisions with maximum efficiency. We can make the box handle most of its contacts itself (so that most of them are internal). To do so, select the box and check High Priority Contacts in the Physics tab (or do it via code).该盒子对我们来说是一个高优先级的物体，我们希望以最大的效率跟踪它的碰撞。 我们可以让盒子自己处理大部分触点（这样大多数触点都是内部的）。 为此，请选中该框并选中Physics选项卡中的High Priority Contacts（或通过代码执行此操作）。

We will use a Particle System to create a node that simulates sparks.我们将使用粒子系统来创建一个模拟火花的节点。

1. In the UnigineEditor, click Create -> Particle System -> Particles. Place the object somewhere in the world, rename it to sparks, and adjust its parameters:在UnigineEditor中，单击Create -> Particle System -> Particles。将对象放置在世界的某个地方，将其重命名为sparks，并调整其参数:

   • Number Per Spawn = 10
   • Radius = 0.02
   • Life Time = 0.2
   • Period = inf
   • Duration = 0
2. In the Surface Material section, assign library_spark1.mat material (it is located in the data -> vfx -> materials -> library_vfx folder of your project).在Surface Material部分中，分配library_spark1.mat材料(它位于项目的data -> vfx -> materials -> library_vfx文件夹中)。
3. Switch to the data folder in the Asset Browser. Right-click the sparks node and select Create a Node Reference. A sparks.node file will be generated in the data folder.在资源浏览器中切换到data文件夹。右键单击sparks节点并选择Create a Node Reference。将在data文件夹中生成一个sparks.node文件。
4. Delete the sparks object from the scene, we no longer need it since it will be loaded via code.从场景中删除sparks对象，我们不再需要它，因为它将通过代码加载。

Let's use the C++ Component System to implement this logic. We will create a C++ component and assign it to the box node.让我们使用 c++组件系统来实现这个逻辑。我们将创建一个c++组件并将其分配给box节点。

1. Open your project in an IDE.在IDE中打开项目。

   注意

   It is recommended to use Visual Studio as a default IDE.建议使用 Visual Studio作为默认IDE。
2. In the IDE create a new C++ class (*.h and *.cpp files) and call it ContactsHandler. Make sure it inherits from the Unigine::ComponentBase class.在IDE中创建一个新的C++类(*.h和*.cpp文件)并将其命名为ContactsHandler。确保它继承自Unigine::ComponentBase类。

3. Copy the code below, paste it to the corresponding files in your project and save them in your IDE.复制下面的代码，将其粘贴到项目中的相应文件中，并将它们保存在IDE中。

   ContactsHandler.h (C++)

   #pragma once
   #include <UnigineComponentSystem.h>
   #include <UnigineGame.h>
   #include <time.h>
   
   class ContactsHandler :
   	public  Unigine::ComponentBase
   {
   public:
   	// declare constructor and destructor for our class and define a property name. 
   	COMPONENT_DEFINE(ContactsHandler, ComponentBase)
   		// declare methods to be called at the corresponding stages of the execution sequence
   		COMPONENT_INIT(init);
   	COMPONENT_UPDATE(update);
   
   	// A node that will be loaded on contact (a hit effect)
   	PROP_PARAM(File, hitEffect);
   
   	bool debug = true;
   
   protected:
   	void init();
   	void update();
   	void OnContactEnter(const Unigine::BodyPtr &, int);
   
   private:
   	// Time, position and some info of the last occurred contact
   	time_t lastContactTime;
   	Unigine::Math::vec3 lastContactPoint;
   	Unigine::String lastContactInfo;
   };

   ContactsHandler.cpp (C++)

   #include "ContactsHandler.h"
   #include <UnigineNode.h>
   #include <UnigineVisualizer.h>
   
   using namespace Unigine;
   using namespace Math;
   
   REGISTER_COMPONENT(ContactsHandler);
   
   void ContactsHandler::init()
   {
   	BodyPtr body = node->getObjectBody();
   	if (body)
   	{
   		// For debug purposes, we can render certain contacts depending on their type    
   		body->getEventContacts().connect([](const BodyPtr &b) {b->renderInternalContacts(); });
   		// subscription for contact event (when each contact emerges)
   		body->getEventContactEnter().connect(this, &ContactsHandler::OnContactEnter);
   	}
   }
   
   // This function takes the body and the index of the contact
   void ContactsHandler::OnContactEnter(const Unigine::BodyPtr &body, int num)
   {
   	// Enable Visualizer to see the rendered contact points
   	Visualizer::setEnabled(true);
   
   	if (body->isContactInternal(num))
   	{
   		if (debug)
   		{
   			// The time of the contact
   			lastContactTime = time(NULL);
   			// The position of the contact
   			lastContactPoint = body->getContactPoint(num);
   
   			// We get both physical bodies participating in this contact
   			BodyPtr body0 = body->getContactBody0(num);
   			BodyPtr body1 = body->getContactBody1(num);
   
   			BodyPtr touchedBody = NULL;
   
   			// We check if our object has hit another physical object.
   			// If any of the bodies exists and it's not the body of our object
   			// then we have found another physics-driven object that hit it
   			if (body0 && body0 != body) touchedBody = body0;
   			if (body1 && body1 != body) touchedBody = body1;
   
   			if (touchedBody)
   			{
   				// Our object has touched a physics-driven object.
   				// We save the info about the body
   				lastContactInfo = String::format("body %s of object %s ", touchedBody->getName(), touchedBody->getObject()->getName());
   				// Render it in the viewport
   				Visualizer::renderObject(touchedBody->getObject(), Math::vec4_blue, 0.5f);
   			}
   			else
   			{
   				// It has touched a surface with Collision enabled
   				lastContactInfo = String::format("surface #%d of object %s", body->getContactSurface(num), body->getContactObject(num)->getName());
   				// Highlighting the surface
   				Visualizer::renderObjectSurface(body->getContactObject(num), body->getContactSurface(num), Math::vec4_blue, 0.5f);
   			}
   
   			// You can add details you are interested in (e.g., the contact impulse)
   			lastContactInfo += String::format("\nimpulse: %f", body->getContactImpulse(num));
   		}
   
   		// We spawn a hit effect if the impulse is strong enough
   		if (body->getContactImpulse(num) > 0.3f && hitEffect)
   		{
   			NodePtr Effect = World::loadNode(hitEffect);
   			Effect->setPosition(Vec3(body->getContactPoint(num)));
   		}
   	}
   
   }
   
   void ContactsHandler::update()
   {
   	// Here we can display the info and create a slow motion effect for one second
   	if (debug)
   	{
   		if (int(time(NULL) - lastContactTime) < 1.0f)
   		{
   			// Slow motion effect
   			Game::setScale(0.3f);
   
   			Visualizer::renderMessage3D(lastContactPoint, Math::vec3_one, ("last contact: \n" + lastContactInfo).get(), Math::vec4_green, 2, 24);
   		}
   		else  // All the other time the speed will be normal
   		{
   			Game::setScale(1.0f);
   		}
   	}
   }

4. Before you can use C++ components, you should initialize the Component System. Modify the init() method of the AppSystemLogic class as shown below (AppSystemLogic.cpp file).在您可以使用c++组件之前，您应该初始化组件系统。修改AppSystemLogic类的init()方法，如下所示(AppSystemLogic.cpp文件)。

   AppSystemLogic.cpp (C++)

   #include <UnigineComponentSystem.h>
   
   int AppSystemLogic::init()
   {
   	// initialize ComponentSystem and register all components
   	ComponentSystem::get()->initialize();
   
   	return 1;
   }

5. Build and run the project via your IDE (press Ctrl + F5 in Visual Studio). The Component System will generate a property file (ContactsHandler.prop) in the data -> ComponentSystem folder of your project.通过IDE构建并运行项目(在Visual Studio中按Ctrl + F5)。组件系统将在项目的data -> ComponentSystem文件夹中生成一个属性文件(ContactsHandler.prop)。

Switch back to the UnigineEditor and select the box node. Click Add New Property in the Parameters window and assign the newly generated ContactsHandler property. Specify the sparks.node asset to be loaded and spawned on collision.切换回UnigineEditor并选择box节点。在Parameters窗口中单击Add New Property，并分配新生成的1_ight属性。指定要在碰撞时加载和生成的sparks.node资源。