OpenGL ES 3.0之顶点缓冲

　　所谓顶点缓冲就是直接将顶点数据存储在gpu的一段缓冲区，不需要从cpu拷贝到gpu。提高了程序的运行效率。

　 操作步骤

　　1.创建顶点缓冲对象

　　

GLuint vertexBufferID;

　　2.分配空间

　　

 glGenBuffers(,  &vertexBufferID);

　　3.绑定当前顶点缓冲对象

　　

   glBindBuffer(GL_ARRAY_BUFFER, vertexBufferID);

　　4.初始化缓冲区数据

　　

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

　　5.启用顶点属性数组

　　

glEnableVertexAttribArray(GLKVertexAttribPosition);

　　6.使用顶点数据进行渲染

   glVertexAttribPointer(
      GLKVertexAttribPosition,
      ,
      GL_FLOAT,
      GL_FALSE,
      sizeof(SceneVertex),
      NULL);    

　　7.绘制

　　

   glDrawArrays(GL_TRIANGLES, ,); 

下面赋全部代码

@interface OpenGLESViewController : GLKViewController
{
   GLuint vertexBufferID;
}

@property (strong, nonatomic) GLKBaseEffect *baseEffect;

@end

#import "OpenGLESViewController.h"

@implementation OpenGLESViewController

@synthesize baseEffect;

/////////////////////////////////////////////////////////////////
// This data type is used to store information for each vertex
typedef struct {
   GLKVector3  positionCoords;
}
SceneVertex;

// Define vertex data for a triangle to use in example
static const SceneVertex vertices[] =
{
   {{-0.5f, -0.5f, 0.0}}, // lower left corner
   {{ 0.5f, -0.5f, 0.0}}, // lower right corner
   {{-0.5f,  0.5f, 0.0}}  // upper left corner
};

/////////////////////////////////////////////////////////////////
// Called when the view controller's view is loaded
// Perform initialization before the view is asked to draw
- (void)viewDidLoad
{
   [super viewDidLoad];

   // Verify the type of view created automatically by the
   // Interface Builder storyboard
   GLKView *view = (GLKView *)self.view;
   NSAssert([view isKindOfClass:[GLKView class]],
      @"View controller's view is not a GLKView");

   // Create an OpenGL ES 2.0 context and provide it to the
   // view
   view.context = [[EAGLContext alloc]
      initWithAPI:kEAGLRenderingAPIOpenGLES2];

   // Make the new context current
   [EAGLContext setCurrentContext:view.context];

   // Create a base effect that provides standard OpenGL ES 2.0
   // Shading Language programs and set constants to be used for
   // all subsequent rendering
   self.baseEffect = [[GLKBaseEffect alloc] init];
   self.baseEffect.useConstantColor = GL_TRUE;
   self.baseEffect.constantColor = GLKVector4Make(
      1.0f, // Red
      1.0f, // Green
      1.0f, // Blue
      1.0f);// Alpha

   // Set the background color stored in the current context
   glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // background color

   // Generate, bind, and initialize contents of a buffer to be
   // stored in GPU memory
   glGenBuffers(,                // STEP 1
      &vertexBufferID);
   glBindBuffer(GL_ARRAY_BUFFER,  // STEP 2
      vertexBufferID);
   glBufferData(                  // STEP 3
      GL_ARRAY_BUFFER,  // Initialize buffer contents
      sizeof(vertices), // Number of bytes to copy
      vertices,         // Address of bytes to copy
      GL_STATIC_DRAW);  // Hint: cache in GPU memory
}

/////////////////////////////////////////////////////////////////
// GLKView delegate method: Called by the view controller's view
// whenever Cocoa Touch asks the view controller's view to
// draw itself. (In this case, render into a frame buffer that
// shares memory with a Core Animation Layer)
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
   [self.baseEffect prepareToDraw];

   // Clear Frame Buffer (erase previous drawing)
   glClear(GL_COLOR_BUFFER_BIT);

   // Enable use of positions from bound vertex buffer
   glEnableVertexAttribArray(      // STEP 4
      GLKVertexAttribPosition);

   glVertexAttribPointer(          // STEP 5
      GLKVertexAttribPosition,
      ,                   // three components per vertex
      GL_FLOAT,            // data is floating point
      GL_FALSE,            // no fixed point scaling
      sizeof(SceneVertex), // no gaps in data
      NULL);               // NULL tells GPU to start at
                           // beginning of bound buffer

   // Draw triangles using the first three vertices in the
   // currently bound vertex buffer
   glDrawArrays(GL_TRIANGLES,      // STEP 6
      ,  // Start with first vertex in currently bound buffer
      ); // Use three vertices from currently bound buffer
}

/////////////////////////////////////////////////////////////////
// Called when the view controller's view has been unloaded
// Perform clean-up that is possible when you know the view
// controller's view won't be asked to draw again soon.
- (void)viewDidUnload
{
   [super viewDidUnload];

   // Make the view's context current
   GLKView *view = (GLKView *)self.view;
   [EAGLContext setCurrentContext:view.context];

   // Delete buffers that aren't needed when view is unloaded
   if ( != vertexBufferID)
   {
      glDeleteBuffers (,          // STEP 7
                       &vertexBufferID);
      vertexBufferID = ;
   }

   // Stop using the context created in -viewDidLoad
   ((GLKView *)self.view).context = nil;
   [EAGLContext setCurrentContext:nil];
}

@end