OpenGL ES实战二-创建立体图形并加载纹理

立体旋转图.gif

OpenGL-ES-loadCubeImage

思路:

一.初始化
这里初始化一些展示相关的类:

- (void)commonInit {
   
    //1.创建context
     EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
    //设置当前context
    [EAGLContext setCurrentContext:context];
    
    //2.创建GLKView并设置代理
    CGRect frame = CGRectMake(0, 100, self.view.frame.size.width, self.view.frame.size.width);
    self.glkView = [[GLKView alloc] initWithFrame:frame context:context];
    self.glkView.backgroundColor = [UIColor clearColor];
    self.glkView.delegate = self;
    
    //3.使用深度缓存
    self.glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    //默认是(0, 1)，这里用于翻转 z 轴，使正方形朝屏幕外
    //glDepthRangef(1, 0);
    
    //4.将GLKView 添加self.view 上
    [self.view addSubview:self.glkView];

    //5.获取纹理图片
    NSString *imagePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"miao.jpeg"];
    UIImage *image = [UIImage imageWithContentsOfFile:imagePath];
    
    //6.设置纹理参数
    NSDictionary *options = @{GLKTextureLoaderOriginBottomLeft : @(YES)};
    GLKTextureInfo *textureInfo = [GLKTextureLoader textureWithCGImage:[image CGImage]
                                                               options:options
                                                                 error:NULL];
  
    //7.使用baseEffect,这里可以把GLKBaseEffect理解为着色器
    self.baseEffect = [[GLKBaseEffect alloc] init];
    self.baseEffect.texture2d0.name = textureInfo.name;
    self.baseEffect.texture2d0.target = textureInfo.target;

}

二.顶点数据
创建顶点数据,并把这些数据拷贝到缓冲的内存中,并且开通Attribute通道,默认是关闭的

-(void)vertexDataSetup
{
    /*
     解释一下:
     这里我们不复用顶点，使用每 3 个点画一个三角形的方式，需要 12 个三角形，则需要 36 个顶点
     以下的数据用来绘制以（0，0，0）为中心，边长为 1 的立方体
     */
    
    //8. 开辟顶点数据空间(数据结构SenceVertex 大小 * 顶点个数kCoordCount)
    self.vertices = malloc(sizeof(CCVertex) * kCoordCount);
    
    // 前面
    self.vertices[0] = (CCVertex){{-0.5, 0.5, 0.5},  {0, 1}};//前面左上角
    self.vertices[1] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 0}};//前面左下角
    self.vertices[2] = (CCVertex){{0.5, 0.5, 0.5},   {1, 1}};//前面右上角
    
    self.vertices[3] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 0}};//前面左下角
    self.vertices[4] = (CCVertex){{0.5, 0.5, 0.5},   {1, 1}};//前面右上角
    self.vertices[5] = (CCVertex){{0.5, -0.5, 0.5},  {1, 0}};//前面右下角
    
    // 上面
    self.vertices[6] = (CCVertex){{0.5, 0.5, 0.5},    {1, 1}};
    self.vertices[7] = (CCVertex){{-0.5, 0.5, 0.5},   {0, 1}};
    self.vertices[8] = (CCVertex){{0.5, 0.5, -0.5},   {1, 0}};
    self.vertices[9] = (CCVertex){{-0.5, 0.5, 0.5},   {0, 1}};
    self.vertices[10] = (CCVertex){{0.5, 0.5, -0.5},  {1, 0}};
    self.vertices[11] = (CCVertex){{-0.5, 0.5, -0.5}, {0, 0}};
    
    // 下面
    self.vertices[12] = (CCVertex){{0.5, -0.5, 0.5},    {1, 1}};
    self.vertices[13] = (CCVertex){{-0.5, -0.5, 0.5},   {0, 1}};
    self.vertices[14] = (CCVertex){{0.5, -0.5, -0.5},   {1, 0}};
    self.vertices[15] = (CCVertex){{-0.5, -0.5, 0.5},   {0, 1}};
    self.vertices[16] = (CCVertex){{0.5, -0.5, -0.5},   {1, 0}};
    self.vertices[17] = (CCVertex){{-0.5, -0.5, -0.5},  {0, 0}};
    
    // 左面
    self.vertices[18] = (CCVertex){{-0.5, 0.5, 0.5},    {1, 1}};
    self.vertices[19] = (CCVertex){{-0.5, -0.5, 0.5},   {0, 1}};
    self.vertices[20] = (CCVertex){{-0.5, 0.5, -0.5},   {1, 0}};
    self.vertices[21] = (CCVertex){{-0.5, -0.5, 0.5},   {0, 1}};
    self.vertices[22] = (CCVertex){{-0.5, 0.5, -0.5},   {1, 0}};
    self.vertices[23] = (CCVertex){{-0.5, -0.5, -0.5},  {0, 0}};
    
    // 右面
    self.vertices[24] = (CCVertex){{0.5, 0.5, 0.5},    {1, 1}};
    self.vertices[25] = (CCVertex){{0.5, -0.5, 0.5},   {0, 1}};
    self.vertices[26] = (CCVertex){{0.5, 0.5, -0.5},   {1, 0}};
    self.vertices[27] = (CCVertex){{0.5, -0.5, 0.5},   {0, 1}};
    self.vertices[28] = (CCVertex){{0.5, 0.5, -0.5},   {1, 0}};
    self.vertices[29] = (CCVertex){{0.5, -0.5, -0.5},  {0, 0}};
    
    // 后面
    self.vertices[30] = (CCVertex){{-0.5, 0.5, -0.5},   {0, 1}};
    self.vertices[31] = (CCVertex){{-0.5, -0.5, -0.5},  {0, 0}};
    self.vertices[32] = (CCVertex){{0.5, 0.5, -0.5},    {1, 1}};
    self.vertices[33] = (CCVertex){{-0.5, -0.5, -0.5},  {0, 0}};
    self.vertices[34] = (CCVertex){{0.5, 0.5, -0.5},    {1, 1}};
    self.vertices[35] = (CCVertex){{0.5, -0.5, -0.5},   {1, 0}};
    
    //开辟缓存区 VBO 顶点缓冲对象(Vertex Buffer Objects)
    //生成一个VBO对象
    glGenBuffers(1, &_vertexBuffer);
    //设置顶点缓冲对象的缓冲类型是GL_ARRAY_BUFFER，将创建的VBO对象绑定到当前的执行程序上，也可以理解为激活
    glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
    GLsizeiptr bufferSizeBytes = sizeof(CCVertex) * kCoordCount;
    //将准备好的顶点数据复制到缓冲的内存中，vertices为顶点数据，GL_STATIC_DRAW表示数据不会改变和几乎不会改变。第三个参数一共有三个选择：GL_STATIC_DRAW 表示数据不会或几乎不会改变、GL_DYNAMIC_DRAW表示数据会被改变很多、GL_STREAM_DRAW 表示数据每次绘制时都会改变。
    glBufferData(GL_ARRAY_BUFFER, bufferSizeBytes, self.vertices, GL_STATIC_DRAW);
    
    //顶点数据
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(CCVertex), NULL + offsetof(CCVertex, positionCoord));
    
    //纹理数据
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(CCVertex), NULL + offsetof(CCVertex, textureCoord));
    
}

三.渲染及更新
这里更新使用的是CADisplayLink,屏幕每次展示新的一帧时调用
渲染在GLKView的代理方法中进行

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {
    
    //1.开启深度测试
    glEnable(GL_DEPTH_TEST);
    //2.清除颜色缓存区&深度缓存区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    //3.准备绘制
    [self.baseEffect prepareToDraw];
    
    //4.绘图
    glDrawArrays(GL_TRIANGLES, 0, kCoordCount);
}