opengles 3.0 hello

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《opengles 3.0编程指南》

#include "esUtil.h"

typedef struct

    GLuint programObject;

} UserData;

//创建着色器，并编译，返回着色器变量

GLuint LoadShader ( GLenum type, const char *shaderSrc )

    GLuint shader;

    GLint compiled;

    //创建着色器对象

    shader = glCreateShader ( type );

    if ( shader == 0 )

        return 0;

    //加载

    glShaderSource ( shader, 1, &shaderSrc, NULL );

    //编译

    glCompileShader ( shader );

    //检查错误

    glGetShaderiv ( shader, GL_COMPILE_STATUS, &compiled );

    if ( !compiled )

        GLint infoLen = 0;

        glGetShaderiv ( shader, GL_INFO_LOG_LENGTH, &infoLen );

        if ( infoLen > 1 )

            char *infoLog = malloc ( sizeof ( char ) * infoLen );

            glGetShaderInfoLog ( shader, infoLen, NULL, infoLog );

            esLogMessage ( "Error compiling shader:\n%s\n", infoLog );

            free ( infoLog );

        glDeleteShader ( shader );

        return 0;

    return shader;

int Init ( ESContext *esContext )

    UserData *userData = esContext->userData;

    char vShaderStr[] =

            "#version 300 es                          \n"

            "layout(location = 0) in vec4 vPosition;  \n"

            "void main()                              \n"

            "{                                        \n"

            "   gl_Position = vPosition;              \n"

            "}                                        \n";

    char fShaderStr[] =

            "#version 300 es                              \n"

            "precision mediump float;                     \n"

            "out vec4 fragColor;                          \n"

            "void main()                                  \n"

            "{                                            \n"

            "   fragColor = vec4 ( 1.0, 0.0, 0.0, 1.0 );  \n"

            "}                                            \n";

    GLuint vertexShader;

    GLuint fragmentShader;

    GLuint programObject;

    GLint linked;

    // 加载着色器

    vertexShader = LoadShader ( GL_VERTEX_SHADER, vShaderStr );

    fragmentShader = LoadShader ( GL_FRAGMENT_SHADER, fShaderStr );

    // 创建着色器对象

    programObject = glCreateProgram ( );

    if ( programObject == 0 )

        return 0;

    // 将顶点着色器和片段着色器连接到programObject上

    glAttachShader ( programObject, vertexShader );

    glAttachShader ( programObject, fragmentShader );

    // 链接

    glLinkProgram ( programObject );

    // 检查错误

    glGetProgramiv ( programObject, GL_LINK_STATUS, &linked );

    if ( !linked )

        GLint infoLen = 0;

        glGetProgramiv ( programObject, GL_INFO_LOG_LENGTH, &infoLen );

        if ( infoLen > 1 )

            char *infoLog = malloc ( sizeof ( char ) * infoLen );

            glGetProgramInfoLog ( programObject, infoLen, NULL, infoLog );

            esLogMessage ( "Error linking program:\n%s\n", infoLog );

            free ( infoLog );

        glDeleteProgram ( programObject );

        return FALSE;

    // Store the program object

    userData->programObject = programObject;

    //将颜色缓冲区赋为白色

    glClearColor ( 1.0f, 1.0f, 1.0f, 0.0f );

    return TRUE;

void Draw ( ESContext *esContext )

    UserData *userData = esContext->userData;

    //设置顶点

    GLfloat vVertices[] = {  0.0f,  0.5f, 0.0f,

                             -0.5f, -0.5f, 0.0f,

                             0.5f, -0.5f, 0.0f

};

    // 设置视口

    glViewport ( 0, 0, esContext->width, esContext->height );

    // Clear the color buffer

    glClear ( GL_COLOR_BUFFER_BIT );

    // 将programObject与程序绑定

    glUseProgram ( userData->programObject );

    // 加载顶点数据

    glVertexAttribPointer ( 0, 3, GL_FLOAT, GL_FALSE, 0, vVertices );

    glEnableVertexAttribArray ( 0 );

    //绘制

    glDrawArrays ( GL_TRIANGLES, 0, 3 );

void Shutdown ( ESContext *esContext )

    UserData *userData = esContext->userData;

    glDeleteProgram ( userData->programObject );

//入口函数 负责分配userDara，创建窗口，初始化回调     //ESContext有一个userData 将所有数据保存在这里面

int esMain ( ESContext *esContext )

    esContext->userData = malloc ( sizeof ( UserData ) );

    esCreateWindow ( esContext, "Hello Triangle", 320, 240, ES_WINDOW_RGB );

    if ( !Init ( esContext ) )

        return GL_FALSE;

    esRegisterShutdownFunc ( esContext, Shutdown );

    esRegisterDrawFunc ( esContext, Draw );

    return GL_TRUE;

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