罗大柚OpenGL ES教程系列LessonTwo（Part 3）：采用VAO和index,绘制一个Cube

同样的， LessonTwo的第三部分我们采用了VAO，但是我们觉得在part 2中那中为创建一个Cube而重复大量顶点数据的方式并不完美，于是我们很自然的想到了用index，part 3就是采用了VAO和index创建的Cube， 这似乎也减少了我们的体力的输出，程序员很幸苦，除了每天要耗费大量的脑力外， 还需要敲打那么多个字符，所以我们尽量的让代码变得简单一点吧，对自己好一点。好了， 代码端上来：

#import "ViewController.h"

 

#define BUFFER_OFFSET(i) ((char *)NULL + (i))

 

typedef struct {

    floatPosition[3];

}Vertex;

 

 

const Vertex Vertices[] = {

    {0.5f, -0.5f,  0.0f},

    {0.5f,  0.5f,  0.0f},

   {-0.5f,  0.5f,  0.0f},

   {-0.5f, -0.5f,  0.0f},

    {0.5f, -0.5f, -0.5f},

    {0.5f,  0.5f, -0.5f},

   {-0.5f,  0.5f, -0.5f},

   {-0.5f, -0.5f, -0.5f}

};

 

const GLubyte Indices[] = {

    // Front

    0,1, 2,

    2,3, 0,

    // Back

    4,5, 6,

    6,7, 4,

    // Left

    4,5, 1,

    1,0, 4,

    // Right

    7,6, 2,

    2, 3, 7,

    // Top

    5,6, 2,

    2,1, 5,

    // Bottom

    4,7, 3,

    3,0, 4,

};

 

@interface ViewController ()

{

    float_rotation;

    GLuint _vertexArray;

    GLuint vertexBufferID;

    GLuint indexBufferID;

}

 

@property (strong, nonatomic) EAGLContext *context;

@property (strong, nonatomic) GLKBaseEffect *effect;

 

- (void)setupGL;

- (void)tearDownGL;

 

@end

 

@implementation ViewController

 

- (void)viewDidLoad

{

    [super viewDidLoad];

         self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];

   

    if (!self.context) {

       NSLog(@"Failed to create ES context");

    }

   

    GLKView *view = (GLKView *)self.view;

   view.context = self.context;

    //

   view.drawableDepthFormat = GLKViewDrawableDepthFormat24;

   

    [self setupGL];

}

 

- (void)setupGL

{

    [EAGLContext setCurrentContext:self.context];

   

    self.effect = [[GLKBaseEffect alloc] init];

   

    self.effect.useConstantColor = GL_TRUE;

    self.effect.constantColor = GLKVector4Make(

                                              1.0f, // Red

                                              0.0f, // Green

                                              0.0f, // Blue

                                               1.0f);// Alpha

    glEnable(GL_DEPTH_TEST);

   

   

    //设置VAO

    glGenVertexArraysOES(1, &_vertexArray);

    glBindVertexArrayOES(_vertexArray);

   

    glGenBuffers(1,                // STEP 1

                 &vertexBufferID);

    glBindBuffer(GL_ARRAY_BUFFER,  // STEP 2

                 vertexBufferID);

    glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);

   

    glEnableVertexAttribArray(      // STEP 4

                              GLKVertexAttribPosition);

   

    glVertexAttribPointer(         // STEP 5

                         GLKVertexAttribPosition,

                          3,                   // three components per vertex

                          GL_FLOAT,            // data is floating point

                          GL_FALSE,            // no fixed point scaling

                          sizeof(Vertex),                    // no gaps in data

                          NULL);               // NULL tells GPU to start at

    

   

    //索引

    glGenBuffers(1, &indexBufferID);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBufferID);

    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(Indices), Indices, GL_STATIC_DRAW);

   

   

    //

    glBindBuffer(GL_ARRAY_BUFFER, 0);

    glBindVertexArrayOES(0);

   

}

 

//tear down 卸载；卸载GL

- (void)tearDownGL

{

    [EAGLContext setCurrentContext:self.context];

   

    glDeleteBuffers(1, &vertexBufferID);

    glDeleteBuffers(1, &indexBufferID);

    glDeleteVertexArraysOES(1, &_vertexArray);

   

    self.effect = nil;

   

}

#pragma mark - GLKView and GLKViewControllerdelegate methods

- (void)update

{

    float aspect= fabsf(self.view.bounds.size.width / self.view.bounds.size.height);

    GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 4.0f, 10.0f);

   

    self.effect.transform.projectionMatrix = projectionMatrix;

   

    GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -7.0f);

   modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, _rotation, 1.0f, 1.0f, 1.0f);

   

    self.effect.transform.modelviewMatrix = modelViewMatrix;

    _rotation += self.timeSinceLastUpdate * 0.5f;

   

}

 

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect

{

    glClearColor(0.65f, 0.65f, 0.65f, 1.0f);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   

    glBindVertexArrayOES(_vertexArray);

   

    // Render the object with GLKit

    [self.effectprepareToDraw];

   

    glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]),

                   GL_UNSIGNED_BYTE, 0);

   

}

 

 

- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

   

    if ([self isViewLoaded] && ([[self view] window] == nil)) {

       self.view = nil;

       

       [self tearDownGL];

       

       if ([EAGLContext currentContext] == self.context) {

           [EAGLContext setCurrentContext:nil];

       }

       self.context = nil;

    }

}

 

- (void)dealloc

{

    [self tearDownGL];

   

    if ([EAGLContext currentContext] == self.context) {

       [EAGLContext setCurrentContext:nil];

    }

}

 

@end

源码链接： http://download.youkuaiyun.com/detail/luozhonglan/6987135