Cocos2d-x中使用OpenGL ES2.0編寫shader

這幾天在看子龍山人的關於OpenGL的文章，先依葫蘆畫瓢，能看到些東西，才能慢慢深刻了解，當入門文章不錯，可是其中遇到的一些問題，折騰了一些時間，爲了方便和我同樣的小白們，在這篇文章中進行寫補充。

OpenGL ES2.0教程：編寫本身的shader(2)--子龍山人

文章中關於VBO和VAO部分的代碼的寫法，我進行了些修改，將重複使用的變量定義全局變量，並修改初始化數據位置，防止在onDraw方法中重複的Malloc，導致內存泄露，具體的修改在代碼註釋中會說明。

源碼以下：

HelloWorldScene.h

 1 #include "cocos2d.h"
 2 
 3 USING_NS_CC;
 4 
 5 class HelloWorld : public cocos2d::Layer
 6 
 7 {
 8 
 9 public:
10 
11   static cocos2d::Scene* createScene();
12 
13   virtual bool init() override;
14 
15   CREATE_FUNC(HelloWorld);
16 
17   virtual void visit(Renderer *renderer, const Mat4& parentTransform,   uint32_t parentFlags) override;
18 
19   void onDraw();
20 
21 private:
22 
23   CustomCommand _command;
24 
25   float _position[16];
26 
27   float _color[12];
28 
29   GLProgram* glProgram;
30 
31   GLuint vao;//定義VAO緩衝
32 
33   GLuint positionVBO;
34 
35   GLuint colorVBO;
36 
37   GLuint positionLocation;
38 
39   GLuint colorLocation;
40 
41 };

HelloWorldScene.cpp

 1 #include "HelloWorldScene.h"
 2 
 3 Scene* HelloWorld::createScene()
 4 {
 5     auto scene = Scene::create();
 6 
 7     auto layer = HelloWorld::create();
 8 
 9     scene->addChild(layer);
10 
11     return scene;
12 }
13 
14 void HelloWorld::visit(Renderer *renderer, const Mat4 &transform,uint32_t parentFlags)
15 {
16     Layer::visit(renderer, transform, parentFlags);
17     _command.init(_globalZOrder);
18     _command.func = CC_CALLBACK_0(HelloWorld::onDraw, this);
19     Director::getInstance()->getRenderer()->addCommand(&_command);
20 }
21 
22 void HelloWorld::onDraw()
23 {
24     //使用已經在init中初始化的glProgram
25     glProgram->use();
26     glProgram->setUniformsForBuiltins();
27 
28     //獲取VAO（OSX和ISO中默認開啓，windows中默認不開啓）
29     glBindVertexArray(vao);
30 
31     //獲取VBO
32     glBindBuffer(GL_ARRAY_BUFFER, positionVBO);
33     //填充座標數據
34     glBufferData(GL_ARRAY_BUFFER, sizeof(_position), _position, GL_STATIC_DRAW);
35     positionLocation = glGetAttribLocation(glProgram->getProgram(), "a_position");
36     glEnableVertexAttribArray(positionLocation);
37     glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
38 
39     //獲取VBO
40     glBindBuffer(GL_ARRAY_BUFFER, colorVBO);
41     //填充顏色數據
42     glBufferData(GL_ARRAY_BUFFER, sizeof(_color), _color, GL_STATIC_DRAW);
43     colorLocation = glGetAttribLocation(glProgram->getProgram(), "a_color");
44     glEnableVertexAttribArray(colorLocation);
45     glVertexAttribPointer(colorLocation, 4, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
46 
47     //使用VAO
48     glBindVertexArray(vao);
49     //渲染
50     glDrawArrays(GL_TRIANGLES, 0, 3);
51     //清空VAO
52     glBindVertexArray(0);
53 
54     CC_INCREMENT_GL_DRAWN_BATCHES_AND_VERTICES(1, 3);
55     CHECK_GL_ERROR_DEBUG();
56 }
57 
58 bool HelloWorld::init()
59 {
60     if ( !Layer::init() )
61     {
62         return false;
63     }
64 
65     //準備數據
66     auto size = Director::getInstance()->getWinSize();
67     float position[] = { 0, 0, size.width, 0, size.width / 2, size.height};
68     float color[] = { 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1};
69     for (int i = 0; i < sizeof(position); i++) {
70         _position[i] = position[i];
71     }
72     for (int i = 0; i < sizeof(color); i++) {
73         _color[i] = color[i];
74     }
75 
76     //vert和frag文件和原文同樣，直接放在Classes目錄就能夠讀取到（環境：XCode）
77     glProgram = new GLProgram;
78     glProgram->initWithFilenames("myVertextShader.vert","myFragmentShader.frag");
79     glProgram->link();
80     glProgram->updateUniforms();
81     this->setGLProgram(glProgram);
82 
83     //glGen的系列方法會不斷的Malloc內存空間，寫在onDraw中會致使內存泄漏
84     glGenVertexArrays(1, &vao);
85     glGenBuffers(1, &positionVBO);
86     glGenBuffers(1, &colorVBO);
87     return true;
88 }

運行結果：