OpenGL ES2.0贴图

1、定义传入着色器的顶点数据及索引

//传入结构体
typedef struct {
    float Position[];
    float TexCoord[];
} Vertex;
//顶点数据
const Vertex Vertices[] = {
    {{, -, }, {, }},
    {{, , },{, }},
    {{-, , }, {, }},
    {{-, -, },{, }},
};
//顶点索引
const GLubyte Indices[] = {
    , , ,
    , ,
};

2、生成图片纹理并获得其索引 方法

+ (GLuint)setupTexture:(UIImage *)pImage {

    CGImageRef spriteImage = pImage.CGImage;
    if (!spriteImage) {
        NSLog(@"Failed to load image ");
        exit();
    }

    size_t width = CGImageGetWidth(spriteImage);
    size_t height = CGImageGetHeight(spriteImage); 

    GLubyte * spriteData = (GLubyte *) calloc(width*height*, sizeof(GLubyte));

    CGContextRef spriteContext = CGBitmapContextCreate(spriteData, width, height, , width*,
                                                       CGImageGetColorSpace(spriteImage), kCGImageAlphaPremultipliedLast);

    CGContextDrawImage(spriteContext, CGRectMake(, , width, height), spriteImage);

    CGContextRelease(spriteContext);

    GLuint texName;
    //生成纹理数
    glGenTextures(, &texName);
    glBindTexture(GL_TEXTURE_2D, texName);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    //生成图片纹理
    glTexImage2D(GL_TEXTURE_2D, , GL_RGBA, width, height, , GL_RGBA, GL_UNSIGNED_BYTE, spriteData);

    free(spriteData);
    return texName;
}

3、获取传入GLSL的槽位

 //获得图片纹理索引
 _imageTexture = [OpenGLHelper setupTexture:pImage];
//获得在GLSL中纹理的索引
   _texCoordSlot = glGetAttribLocation(_programHandle, "TexCoordIn");
    glEnableVertexAttribArray(_texCoordSlot);
    _textureUniform = glGetUniformLocation(_programHandle, "Texture");
//获得GLSL中顶点的索引
   _positionSlot = glGetAttribLocation(_programHandle, "vPosition");

4、在render(渲染)方法中加入

     //传入顶点着色器的数据
    glVertexAttribPointer(_positionSlot, , GL_FLOAT, GL_FALSE,
                          sizeof(Vertex), );
    glVertexAttribPointer(_texCoordSlot, , GL_FLOAT, GL_FALSE,
                          sizeof(Vertex), (GLvoid*) (sizeof(float) *
                                                     ));

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, _imageTexture);
    glUniform1i(_textureUniform, );

    // 设置边缘截取模式  防止图片读取有问题
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[]),
                   GL_UNSIGNED_BYTE, );