GLKit绘制立方体

• 在ViewController中定义相关属性

  typedef struct {
      GLKVector3 positionCoord;
      GLKVector3 textureCoord;
  } HYVertex;
  
  static GLint const kCoordCount = 24;
  static GLint const kFaceCount = 6;
  static GLint const kFaceVertexCount = 4;
  
  @interface CubeViewController ()<GLKViewDelegate>
  {
      HYVertex *vertices;
      GLuint vertexBuffer;
      GLint angle;
  }
  
  @property (nonatomic, strong) GLKView *glkView;
  
  @property (nonatomic, strong) GLKBaseEffect *baseEffect;
  
  @property (nonatomic, strong) CADisplayLink *displayLink;
  
  @end
  

• 初始化EAGLContext

  EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
  [EAGLContext setCurrentContext:context];
  

• 添加GLKView

  self.glkView = [[GLKView alloc] initWithFrame:CGRectMake(0, 100, self.view.bounds.size.width, self.view.bounds.size.width) context:context];
  self.glkView.delegate = self;
  self.glkView.backgroundColor = [UIColor clearColor];
  [self.view addSubview:self.glkView];
  

• 设置深度缓存区和颜色缓存区格式

  self.glkView.drawableColorFormat = GLKViewDrawableColorFormatRGBA8888;
  self.glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
  

• 初始化顶点数据

  // 开辟顶点数据空间
      vertices = malloc(sizeof(HYVertex) * kCoordCount);
      
      // 前面
      vertices[0] = (HYVertex){{0.5, -0.5, 0.5}, {1, 0}, {0, 0, 1}};
      vertices[1] = (HYVertex){{-0.5, -0.5, 0.5}, {0, 0}, {0, 0, 1}};
      vertices[2] = (HYVertex){{0.5, 0.5, 0.5}, {1, 1}, {0, 0, 1}};
      vertices[3] = (HYVertex){{-0.5, 0.5, 0.5}, {0, 1}, {0, 0, 1}};
      
      // 后面
      vertices[4] = (HYVertex){{-0.5, 0.5, -0.5}, {0, 1}, {0, 0, -1}};
      vertices[5] = (HYVertex){{0.5, 0.5, -0.5}, {1, 1}, {0, 0, -1}};
      vertices[6] = (HYVertex){{-0.5, -0.5, -0.5}, {0, 0}, {0, 0, -1}};
      vertices[7] = (HYVertex){{0.5, -0.5, -0.5}, {1, 0}, {0, 0, -1}};
      
      // 上面
      vertices[8] = (HYVertex){{0.5, 0.5, 0.5}, {1, 0}, {0, 1, 0}};
      vertices[9] = (HYVertex){{-0.5, 0.5, 0.5}, {0, 0}, {0, 1, 0}};
      vertices[10] = (HYVertex){{0.5, 0.5, -0.5}, {1, 1}, {0, 1, 0}};
      vertices[11] = (HYVertex){{-0.5, 0.5, -0.5}, {0, 1}, {0, 1, 0}};
      
      // 下面
      vertices[12] = (HYVertex){{-0.5, -0.5, -0.5}, {0, 0}, {0, -1, 0}};
      vertices[13] = (HYVertex){{0.5, -0.5, -0.5}, {1, 0}, {0, -1, 0}};
      vertices[14] = (HYVertex){{-0.5, -0.5, 0.5}, {0, 1}, {0, -1, 0}};
      vertices[15] = (HYVertex){{0.5, -0.5, 0.5}, {1, 1}, {0, -1, 0}};
      
      // 左面
      vertices[16] = (HYVertex){{-0.5, -0.5, -0.5}, {0, 0}, {-1, 0, 0}};
      vertices[17] = (HYVertex){{-0.5, -0.5, 0.5}, {1, 0}, {-1, 0, 0}};
      vertices[18] = (HYVertex){{-0.5, 0.5, -0.5}, {0, 1}, {-1, 0, 0}};
      vertices[19] = (HYVertex){{-0.5, 0.5, 0.5}, {1, 1}, {-1, 0, 0}};
      
      // 右面
      vertices[20] = (HYVertex){{0.5, 0.5, -0.5}, {1, 1}, {1, 0, 0}};
      vertices[21] = (HYVertex){{0.5, 0.5, 0.5}, {0, 1}, {1, 0, 0}};
      vertices[22] = (HYVertex){{0.5, -0.5, -0.5}, {1, 0}, {1, 0, 0}};
      vertices[23] = (HYVertex){{0.5, -0.5, 0.5}, {0, 0}, {1, 0, 0}};
  

• 开辟顶点缓存区(VBO)

  glGenBuffers(1, &vertexBuffer);
  glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
  glBufferData(GL_ARRAY_BUFFER, sizeof(HYVertex) * kCoordCount, vertices, GL_STATIC_DRAW);
  

• 开启顶点、纹理坐标属性通道，设置顶点、纹理坐标的读取方式

  glEnableVertexAttribArray(GLKVertexAttribPosition);
  glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(HYVertex), NULL + offsetof(HYVertex, positionCoord));
      
  glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
  glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(HYVertex), NULL + offsetof(HYVertex, textureCoord));
  

• 载入纹理 & 创建GLKBaseEffect

  NSString *path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"2.jpg"];
      
  GLKTextureInfo *tetureInfo = [GLKTextureLoader textureWithContentsOfFile:path options:@{GLKTextureLoaderOriginBottomLeft : @(GL_TRUE)} error:nil];
      
  self.baseEffect = [[GLKBaseEffect alloc] init];
  self.baseEffect.texture2d0.name = tetureInfo.name;
  self.baseEffect.texture2d0.target = tetureInfo.target;
  

• 实现GLKViewDelegate方法进行图形绘制

  - (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {
      
      glEnable(GL_DEPTH_TEST);
      
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      
      [self.baseEffect prepareToDraw];
      
      for (GLint i = 0; i < kFaceCount; i++) {
          glDrawArrays(GL_TRIANGLE_STRIP, i * kFaceVertexCount, kFaceVertexCount);
      }
  }
  
  

• 添加CADisplayLink让立方体自动旋转

  angle = 0;
  self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
  [self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
  

• 重新绘制

  - (void)update {
      angle = (angle + 5) % 360;
      self.baseEffect.transform.modelviewMatrix = GLKMatrix4MakeRotation(GLKMathDegreesToRadians(angle), 0.3, 0.7, 0.2);
      [self.glkView display];
  }
  
  

完整的Demo