学习链接：中文------英语原文

这一节在上一节的基础上添加了碰撞检测：有两种形状的检测：方形和方形，方形和圆形
具体理论看上面链接。

Game.cpp：

#include "ResourceManager.h"
#include "Game.h"
#include "SpriteRenderer.h"
#include "BallObject.h"

SpriteRenderer* renderer;

Game::Game(GLuint w, GLuint h) :state(GAME_ACTIVE), keys(), width(w), height(h)
{
}

Game::~Game()
{
}

//player
const glm::vec2 PLAYER_SIZE(100, 20);
const GLfloat PLAYER_VELOCITY(500.0f);
GameObject* player;


//ball init velocity
const glm::vec2 INITIAL_BALL_VELOCITY(100.0f, -350.0f);
//ball radius
const GLfloat BALL_RADIUS = 12.5f;

BallObject* ball;

void Game::Init()
{
	//load shader
	ResourceManager::LoadShader("Shaders/Breakout/Sprite.vs", "Shaders/Breakout/Sprite.fs", nullptr, "sprite");
	//config shader
	glm::mat4 projection = glm::ortho(0.0f, static_cast<GLfloat>(this->width), static_cast<GLfloat>(this->height), 0.0f, -1.0f, 1.0f);
	ResourceManager::GetShader("sprite").Use().SetInteger("image", 0);
	ResourceManager::GetShader("sprite").SetMatrix4("projection", projection);
	//setup render control
	renderer = new SpriteRenderer(ResourceManager::GetShader("sprite"));
	//load texture
	ResourceManager::LoadTexture("Breakout/Images/background.jpg", GL_TRUE, "background");
	ResourceManager::LoadTexture("Breakout/Images/block.png", GL_FALSE, "block");
	ResourceManager::LoadTexture("Breakout/Images/block_solid.png", GL_FALSE, "block_solid");
	ResourceManager::LoadTexture("Breakout/paddle.png", true, "paddle");//player
	ResourceManager::LoadTexture("Breakout/face.png", true, "ball");//ball
	//load levels
	GameLevel one; one.Load("Breakout/Levels/1.lvl", this->width, this->height * 0.5);
	GameLevel two; two.Load("Breakout/Levels/2.lvl", this->width, this->height * 0.5);
	GameLevel three; three.Load("Breakout/Levels/3.lvl", this->width, this->height * 0.5);
	GameLevel four; four.Load("Breakout/Levels/4.lvl", this->width, this->height * 0.5);

	this->levels.push_back(one);
	this->levels.push_back(two);
	this->levels.push_back(three);
	this->levels.push_back(four);
	this->currentLevel = 0;

	//player init
	glm::vec2 playerPos = glm::vec2(this->width / 2 - PLAYER_SIZE.x / 2, this->height - PLAYER_SIZE.y);
	player = new GameObject(playerPos, PLAYER_SIZE, ResourceManager::GetTexture("paddle"));

	//ball init    原点位置是左上角
	glm::vec2 ballPos = playerPos + glm::vec2(PLAYER_SIZE.x / 2 - BALL_RADIUS, -BALL_RADIUS * 2);
	ball = new BallObject(ballPos, BALL_RADIUS, INITIAL_BALL_VELOCITY, ResourceManager::GetTexture("ball"));
}

void Game::ProcessInput(GLfloat dt)
{
	if (this->state == GAME_ACTIVE)
	{
		GLfloat velocity = PLAYER_VELOCITY * dt;
		//移动挡板
		if (this->keys[GLFW_KEY_A])
		{
			if (player->position.x >= 0)
			{
				player->position.x -= velocity;

				if (ball->stuck)
					ball->position.x -= velocity;
			}
		}
		if (this->keys[GLFW_KEY_D])
		{
			if (player->position.x <= this->width - player->size.x)
			{
				player->position.x += velocity;
				if (ball->stuck)
					ball->position.x += velocity;
			}
		}
		if (this->keys[GLFW_KEY_SPACE])
			ball->stuck = false;
	}
}

void Game::Update(GLfloat dt)
{
	//update ball
	ball->Move(dt, this->width);

	//collision detection
	this->DoCollisions();
}

void Game::Render()
{
	if (this->state == GAME_ACTIVE)
	{
		//绘制背景
		renderer->DrawSprite(ResourceManager::GetTexture("background"), glm::vec2(0, 0), glm::vec2(this->width, this->height), 0.0f);

		//绘制关卡
		this->levels[this->currentLevel].Draw(*renderer);

		//绘制玩家挡板
		player->Draw(*renderer);

		//绘制球
		ball->Draw(*renderer);
	}
}

//碰撞检测：：AABB
GLboolean CheckCollision(GameObject& one, GameObject& two) // AABB - AABB collision
{
	// x轴方向碰撞？
	bool collisionX = one.position.x + one.size.x >= two.position.x &&
		two.position.x + two.size.x >= one.position.x;
	// y轴方向碰撞？
	bool collisionY = one.position.y + one.size.y >= two.position.y &&
		two.position.y + two.size.y >= one.position.y;
	// 只有两个轴向都有碰撞时才碰撞
	return collisionX && collisionY;
}

//碰撞检测：方形和圆形
GLboolean CheckCollision(BallObject& one, GameObject& two) // AABB - Circle collision
{
	//获取圆的中心
	glm::vec2 center(one.position+one.radius);
	//计算AABB的信息（中心，半边长）
	glm::vec2 aabb_half_extents(two.size.x/2,two.size.y/2);
	glm::vec2 aabb_center(two.position.x+aabb_half_extents.x,two.position.y+aabb_half_extents.y);
	//获取两个中心的差矢量
	glm::vec2 difference=center-aabb_center;
	glm::vec2 clamped=glm::clamp(difference,-aabb_half_extents,aabb_half_extents);
	//AABB_center 加上clampled这样就得到了碰撞箱上距离最近点closest
	glm::vec2 closest=aabb_center+clamped;
	//获得圆心center和最近点closest的矢量，并判断是否length<=radius
	difference=closest-center;
	return glm::length(difference)<one.radius;	
}

void Game::DoCollisions()
{
	for (GameObject& box : this->levels[this->currentLevel].bricks)
	{
		if (!box.destroyed)
		{
			if (CheckCollision(*ball,box))
			{
				if (!box.isSoild)
					box.destroyed = GL_TRUE;
			}
		}
	}
}