cocos2dx opengl入门系列二-画一个三角形

运行环境：

mac10.12.2

xcode Version 8.2.1

cocos2dx-x-3.13.1

代码：

新建cocos2dx项目，具体操作官网有教程。新建好后，

新建Test.cpp，代码如下：

////  Test.cpp//  FirstTriangle////  Created by zhufu on 2017/3/27.////#include "Test.h"Test* Test::create(){    Test* test = new(std::nothrow) Test();    if(test && test->init())    {        test->autorelease();        return test;    }    else    {        delete test;        test = nullptr;        return nullptr;    }}bool Test::init(){    _glProgram = new GLProgram();    _glProgram->initWithFilenames("shader/myVertexShader.vsh", "shader/myFragmentShader.fsh");    _glProgram->link();    //set uniform locations    //使用此shader    _glProgram->use();                GLuint vertexVBO, colorVBO;    glGenVertexArrays(1, &_vao);    glBindVertexArray(_vao);        //创建和绑定vbo    glGenBuffers(1, &vertexVBO);    glBindBuffer(GL_ARRAY_BUFFER, vertexVBO);        GLfloat vertexData[] = {        //  X     Y     Z        0.0f, 1.0f, 0.0f,        -1.0f,-1.0f, 0.0f,        1.0f,-1.0f, 0.0f,    };    glBufferData(GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW);        //获取vertex attribute "a_position"的入口点    GLuint positionLocation = glGetAttribLocation(_glProgram->getProgram(), "a_position");    //打开入a_position入口点    glEnableVertexAttribArray(positionLocation);    //传递顶点数据给a_position，注意最后一个参数是数组的偏移了。    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);        //set for color    glGenBuffers(1, &colorVBO);    glBindBuffer(GL_ARRAY_BUFFER, colorVBO);    float color[] = {0,1,0,1,  1,0,0,1,  0,0,1,1};    glBufferData(GL_ARRAY_BUFFER, sizeof(color), color, GL_STATIC_DRAW);        GLuint colorLocation = glGetAttribLocation(_glProgram->getProgram(), "a_color");    glEnableVertexAttribArray(colorLocation);    glVertexAttribPointer(colorLocation, 4, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);        _command.init(_globalZOrder);    _command.func = CC_CALLBACK_0(Test::onDraw, this);        return true;}void Test::draw(Renderer *renderer, const Mat4 &parentTransform, uint32_t parentFlags){        Director::getInstance()->getRenderer()->addCommand(&_command);}void Test::onDraw(){    glClearColor(0, 0, 0, 1); // black    glClear(GL_COLOR_BUFFER_BIT);        // bind the program (the shaders)    glUseProgram(_glProgram->getProgram());    // bind the VAO (the triangle)    glBindVertexArray(_vao);        // draw the VAO    glDrawArrays(GL_TRIANGLES, 0, 3);    // unbind the VAO    glBindVertexArray(0);        // unbind the program    glUseProgram(0);}

新建Test.h，代码如下：

////  Test.h//  FirstTriangle////  Created by zhufu on 2017/3/27.////#ifndef Test_h#define Test_h#include <stdio.h>USING_NS_CC;class Test : public Node{public:    GLuint _program = 0;    virtual bool init() override;    static Test* create();    virtual void draw(Renderer *renderer, const Mat4& parentTransform, uint32_t parentFlags) override;    void onDraw();        cocos2d::CustomCommand _command;    GLProgram* _glProgram;        GLuint _vao = 0;    GLuint _vertexVBO = 0;    GLuint _colorVBO = 0;};#endif /* Test_h */

如图：

修改HelloWorldScene.cpp，

先

include "Test.h"

再修改CreateScene方法：

Scene* HelloWorld::createScene(){    // 'scene' is an autorelease object    auto scene = Scene::create();        auto test = Test::create();    scene->addChild(test);        // 'layer' is an autorelease object    auto layer = HelloWorld::create();    // add layer as a child to scene    scene->addChild(layer);    // return the scene    return scene;}

如图：

在Resources方位夹下新建shader文件夹，再在shader新建myVertexShader.vsh和myFragmentShader.fsh文件。

如图：

myVertexShader.vsh

attribute vec4 a_position;attribute vec4 a_color;varying vec4 v_fragmentColor;void main(){    gl_Position = a_position;    v_fragmentColor = a_color;}

myFragmentShader.fsh

varying vec4 v_fragmentColor;void main(){    gl_FragColor = v_fragmentColor;}

接下来，可以开心地运行程序了。

运行效果：