OpenCV for Ios 学习笔记(8)－用OPENGL渲染AR场景1

本文原始地址：OpenCV for Ios 学习笔记(8)－用OPENGL渲染AR场景1

 创建OpenGL渲染层

为了在你的应用中使用opengl函数，你必须为你的应用添加一个图形画板，它给用户呈现被渲染的场景。

为了封装opengl画板初始化逻辑，我们介绍EAGLView类：

//
//  EAGLView.h
//  OpenCvDemo
//
//  Created by apple on 13-4-24.
//  Copyright (c) 2013年 hxy. All rights reserved.
//

#import <UIKit/UIKit.h>
#import <OpenGLES/ES1/gl.h>
#import <OpenGLES/ES1/glext.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>

@class EAGLContext;
@interface EAGLView : UIView
{
    @private
    GLuint defaultFrameBuffer,colorRenderBuffer,depthRenderBuffer;
}
@property (nonatomic, retain) EAGLContext *context;
@property (readonly) GLint frameBufferWidth,frameBufferHeight;
//初始化画板
- (void)initContext;
//设置帧缓存
- (void)setFrameBuffer;
//呈现帧缓存
- (void)presentFrameBuffer;
@end

//
//  EAGLView.m
//  OpenCvDemo
//
//  Created by apple on 13-4-24.
//  Copyright (c) 2013年 hxy. All rights reserved.
//

#import "EAGLView.h"

@interface EAGLView (Private)
//创建帧缓存
- (void)createFrameBuffer;
//删除所有的缓存
- (void)deleteFrameBuffer;
@end

@implementation EAGLView
@synthesize context,frameBufferHeight,frameBufferWidth;

- (void)dealloc
{
    [self deleteFrameBuffer];
    if ([EAGLContext currentContext] == context)
    {
        [EAGLContext setCurrentContext:nil];
    }
    [super dealloc];
}

+ (Class)layerClass
{
    return [CAEAGLLayer class];
}

- (void)layoutSubviews
{
    //在下一次设置帧缓存时，帧缓存将会重新创建
    [self deleteFrameBuffer];
}

- (void)initContext
{
    if (!context)
    {
        EAGLRenderingAPI api = kEAGLRenderingAPIOpenGLES2;
        context = [[EAGLContext alloc] initWithAPI:api];
        if (!context)
        {
            NSLog(@"画布都创建失败，还运行个闯闯！");
            exit(1);
            return;
        }
        if (![EAGLContext setCurrentContext:context])
        {
            NSLog(@"悲剧了塞！");
            exit(1);
            return;
        }
    }
}

- (void)setContext:(EAGLContext *)newcontext
{
    if (context != newcontext)
    {
        [self deleteFrameBuffer];
        context = newcontext;
        [EAGLContext setCurrentContext:nil];
    }
}

- (CAEAGLLayer *)myLayer
{
    return (CAEAGLLayer *)self.layer;
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super initWithCoder:aDecoder])
    {
        CAEAGLLayer *layer = [self myLayer];
        layer.opaque = TRUE;
        layer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:FALSE],kEAGLDrawablePropertyRetainedBacking,kEAGLColorFormatRGBA8,kEAGLDrawablePropertyColorFormat, nil];
        [self initContext];
    }
    return self;
}

- (void)setFrameBuffer
{
    if (context)
    {
        [EAGLContext setCurrentContext:context];
        if (!depthRenderBuffer)
        {
            [self createFrameBuffer];
        }
        
        glBindFramebuffer(GL_FRAMEBUFFER, defaultFrameBuffer);
        glViewport(0, 0, frameBufferWidth, frameBufferHeight);
        glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    }
}

- (void)presentFrameBuffer
{
    BOOL success = FALSE;
    if (context)
    {
        [EAGLContext setCurrentContext:context];
        
        glBindRenderbuffer(1, colorRenderBuffer);
        success = [context presentRenderbuffer:GL_RENDERBUFFER];
    }
}

- (void)createFrameBuffer
{
    //还未设置默认帧缓存
    if (context && !defaultFrameBuffer)
    {
        [EAGLContext setCurrentContext:context];
        
        //创建默认帧缓存对象
        glGenFramebuffers(1, &(defaultFrameBuffer));
        glBindFramebuffer(GL_FRAMEBUFFER, defaultFrameBuffer);
        
        //创建颜色缓存，分配内存
        glGenRenderbuffers(1, &colorRenderBuffer);
        glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer);
        
        [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:[self myLayer]];
        
        glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &frameBufferWidth);
        glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &frameBufferHeight);
        
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderBuffer);
        //生成深度缓存
        glGenRenderbuffers(1, &depthRenderBuffer);
        glBindRenderbuffer(GL_RENDERBUFFER, depthRenderBuffer);
        
        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, frameBufferWidth, frameBufferHeight);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderBuffer);
        
        //检查状态
        if (glCheckFramebufferStatus(GL_FRAMEBUFFER)!= GL_FRAMEBUFFER_COMPLETE)
        {
            NSLog(@"Failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
        }
    }
}

- (void)deleteFrameBuffer
{
    if (context)
    {
        [EAGLContext setCurrentContext:context];
        
        if (defaultFrameBuffer)
        {
            glDeleteFramebuffers(1, &defaultFrameBuffer);
            defaultFrameBuffer = 0;
        }
        
        if (colorRenderBuffer)
        {
            glDeleteRenderbuffers(1, &colorRenderBuffer);
            colorRenderBuffer = 0;
        }
        
        if (depthRenderBuffer)
        {
            glDeleteRenderbuffers(1, &depthRenderBuffer);
            depthRenderBuffer = 0;
        }
    }
}

@end

在上面的EAGLView并不包括任何的3维物体虚拟化的方法，当然，我们是故意的。EAGLView的任务是提供渲染的画板，将各个类的职责区别开有利于我们在接下来改变虚拟化过程的逻辑。

为了实现增强现实的虚拟化，我们将会创建一个单独的类VisualizationController：

@interface SimpleVisualizationController : NSObject
{
  EAGLView * m_glview;
  GLuint m_backgroundTextureId;
  std::vector<Transformation> m_transformations;
  CameraCalibration m_calibration;
  CGSize m_frameSize;
}

-(id) initWithGLView:(EAGLView*)view calibration:(CameraCalibration) calibration frameSize:(CGSize) size;
//把ar渲染到EAGLView目标视图上去
-(void) drawFrame;
-(void) updateBackground:(BGRAVideoFrame) frame;
-(void) setTransformationList:(const std::vector<Transformation>&) transformations;

@end

未完