深度缓冲

深度测试相关知识点：

• 1、frambuffer 绑定能够管理 多个renderbuffer，然后renderbuffer 可以是深度缓冲区 模板缓冲区以及颜色缓冲区等。

• 2、默认情况下苹果在创建工程时，并没有提供深度缓冲区。所以iOS openGLES必须设置深度缓冲区才能开启深度检测，设置深度相关操作。同时必须绑定颜色缓冲区进行渲染，当然这里不需离屏渲染，所以不需要给myColorRenderBuffer设置纹理内存空间。

相应设置代码如下：

//3.清空缓存区
-(void)deleteBuffer
{
    if (_myColorRenderBuffer) {
        glDeleteRenderbuffers(1, &_myColorRenderBuffer);
        _myColorRenderBuffer = 0;
    }
    
    if (_myDepthRenderBuffer) {
        glDeleteRenderbuffers(1, &_myDepthRenderBuffer);
        _myDepthRenderBuffer = 0;
    }
    
    if (_myColorFrameBuffer) {
        glDeleteFramebuffers(1, &_myColorFrameBuffer);
    }
}
//4.设置RenderBuffer 关联颜色缓冲区
-(void)setupColorRenderBuffer
{
    glGenRenderbuffers(1, &_myColorRenderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, _myColorRenderBuffer);
    
    [self.myContext renderbufferStorage:GL_RENDERBUFFER fromDrawable:self.myEagLayer];
    
    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &_viewWidth);
    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &_viewHeight);
    glBindRenderbuffer(GL_RENDERBUFFER, 0);
}

//关联深度缓冲区
- (void)setDepthRenderBuffer{
    
    glGenRenderbuffers(1, &_myDepthRenderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, _myDepthRenderBuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, _viewWidth, _viewHeight);
    glBindRenderbuffer(GL_RENDERBUFFER, 0);
    
}
//5.设置FrameBuffer 并且绑定颜色和深度的渲染缓冲区 来管理renderbuffer
-(void)setupFrameBuffer{
    glGenFramebuffers(1, &_myColorFrameBuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, _myColorFrameBuffer);
    
    if (_myColorRenderBuffer) {
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _myColorRenderBuffer);
    }
    
    if (_myDepthRenderBuffer) {
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _myDepthRenderBuffer);
    }
}

效果如下：