OpenGL ES之GLKit索引绘制“金字塔”及渲染纹理和颜色混合

准备工作

• 定义需要使用的全部变量：

@property (nonatomic, strong) EAGLContext   *mContext;
@property (nonatomic, strong) GLKBaseEffect *mEffect;

@property (nonatomic, assign) int count;

// 旋转的度数
@property (nonatomic, assign) float XDegree;
@property (nonatomic, assign) float YDegree;
@property (nonatomic, assign) float ZDegree;

// 是否旋转X,Y,Z
@property (nonatomic, assign) BOOL XB;
@property (nonatomic, assign) BOOL YB;
@property (nonatomic, assign) BOOL ZB;

• 定义一个定时器：

    dispatch_source_t timer;

索引绘制

• 新建图层

- (void)setupContext {
    self.mContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    
    if (!_mContext) {
        NSLog(@"Creat failed");
    }
    [EAGLContext setCurrentContext:self.mContext];

    GLKView *view = (GLKView *)self.view;
    view.context = self.mContext;
    view.drawableColorFormat = GLKViewDrawableColorFormatRGBA8888;
    view.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    
    glEnable(GL_DEPTH_TEST);

}

• 设置顶点数据和索引绘制数组

	// 顶点数组
    GLfloat attrArr[] =
    {
        -0.5f, 0.5f, 0.0f,      1.0f, 0.0f, 1.0f, //左上
        0.5f, 0.5f, 0.0f,       1.0f, 0.0f, 1.0f, //右上
        -0.5f, -0.5f, 0.0f,     1.0f, 1.0f, 1.0f, //左下
        
        0.5f, -0.5f, 0.0f,      1.0f, 1.0f, 1.0f, //右下
        0.0f, 0.0f, 1.0f,       0.0f, 1.0f, 0.0f, //顶点
    };
    
    // 绘制索引数组
    GLuint indices[] =
    {
        0, 3, 2,
        0, 1, 3,
        0, 2, 4,
        0, 4, 1,
        2, 3, 4,
        1, 4, 3,
    };

• 计算顶点个数

    // 顶点个数
    self.count = sizeof(indices) /sizeof(GLuint);

• 将顶点数组放入数组缓冲区中 GL_ARRAY_BUFFER

	// 将顶点数组放入数组缓冲区中 GL_ARRAY_BUFFER
    GLuint buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(attrArr), attrArr, GL_STATIC_DRAW);

• 将索引数组存储到索引缓冲区 GL_ELEMENT_ARRAY_BUFFER

	// 将索引数组存储到索引缓冲区 GL_ELEMENT_ARRAY_BUFFER
    GLuint index;
    glGenBuffers(1, &index);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

• 使用顶点数据和颜色数据

	// 使用顶点数据
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, NULL);
   
    // 使用颜色数据
    glEnableVertexAttribArray(GLKVertexAttribColor);
    glVertexAttribPointer(GLKVertexAttribColor, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, (GLfloat *)NULL + 3);

• 初始化着色器

	// 着色器
    self.mEffect = [[GLKBaseEffect alloc] init];

• 创建投影视图矩阵和模型视图矩阵

	// 投影视图
    CGSize size = self.view.bounds.size;
    float aspect = fabs(size.width / size.height);
    GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(90.0), aspect, 0.1f, 100.0);
    projectionMatrix = GLKMatrix4Scale(projectionMatrix, 1.0f, 1.0f, 1.0f);
    self.mEffect.transform.projectionMatrix = projectionMatrix;
    
    // 模型视图
    GLKMatrix4 modelViewMatrix = GLKMatrix4Translate(GLKMatrix4Identity, 0.0f, 0.0f, -2.0f);
    self.mEffect.transform.modelviewMatrix = modelViewMatrix;

• 创建一个定时器用来旋转金字塔

	// 定时器
    double seconds = 0.1;
    timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());
    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, seconds * NSEC_PER_SEC, 0.0);
    dispatch_source_set_event_handler(timer, ^{
       
        self.XDegree += 0.1f * self.XB;
        self.YDegree += 0.1f * self.YB;
        self.ZDegree += 0.1f * self.ZB ;
        
    });
    dispatch_resume(timer);

• 开始绘制

 - (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {
    glClearColor(0.3f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    [self.mEffect prepareToDraw];
    glDrawElements(GL_TRIANGLES, self.count, GL_UNSIGNED_INT, 0);
}

• 效果展示
  

纹理渲染

• 修改顶点数组

	GLfloat attrArr[] =
    {
        -0.5f, 0.5f, 0.0f,      1.0f, 0.0f, 1.0f,    0.0f, 1.0f, // 左上0
        0.5f, 0.5f, 0.0f,       1.0f, 0.0f, 1.0f,    1.0f, 1.0f, // 右上1
        -0.5f, -0.5f, 0.0f,     1.0f, 1.0f, 1.0f,    0.0f, 0.0f, // 左下2
        
        0.5f, -0.5f, 0.0f,      1.0f, 1.0f, 1.0f,    1.0f, 0.0f, // 右下3
        0.0f, 0.0f, 1.0f,       0.0f, 1.0f, 0.0f,    0.5f, 1.0f, // 顶点4
    };

• 使用顶点数据、颜色数据、纹理数据

 	// 使用顶点数据
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 8, NULL);
   
    // 使用颜色数据
    glEnableVertexAttribArray(GLKVertexAttribColor);
    glVertexAttribPointer(GLKVertexAttribColor, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 8, (GLfloat *)NULL + 3);
    // 纹理
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(GLfloat)*8, (GLfloat *)NULL+6);

• 加载纹理

	// 纹理加载
    NSString *filePath = [[NSBundle mainBundle]pathForResource:@"green" ofType:@"png"];
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:@"1",GLKTextureLoaderOriginBottomLeft, nil];
    GLKTextureInfo *textureInfo = [GLKTextureLoader textureWithContentsOfFile:filePath options:options error:nil];
    
    self.mEffect = [[GLKBaseEffect alloc]init];
    self.mEffect.texture2d0.enabled = GL_TRUE;
    self.mEffect.texture2d0.name = textureInfo.name;

颜色混合

	glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

• 效果展示