无法使用 glGenFramebuffers 生成帧缓冲区

Posted 2023-02-16

【中文标题】无法使用 glGenFramebuffers 生成帧缓冲区

【英文标题】：Can't generate framebuffer with glGenFramebuffers

【发布时间】：2012-11-02 05:16:16

【问题描述】：

glGenFramebuffers 不分配帧缓冲区对象！我无法让这个小程序运行。

代码：

/* ----- AppDelegate.h ----- */
#import <UIKit/UIKit.h>

#import "GLView.h"

@interface AppDelegate : NSObject <UIApplicationDelegate>
@private
    UIWindow *window;
    GLView *view;


@end

---

/* ----- AppDelegate.h ----- */

#import "AppDelegate.h"

@implementation AppDelegate

- (void)dealloc

    [view release];
    [window release];
    [super dealloc];


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

    CGRect frame = [[UIScreen mainScreen] bounds];

    window = [[UIWindow alloc] initWithFrame:frame];
    view = [[GLView alloc] initWithFrame:frame];

    [window addSubview:view];
    [window makeKeyAndVisible];
    return YES;


@end

---

/* ----- GLView.h ----- */

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

@interface GLView : UIView
@private
    EAGLContext* context;
    GLuint color_render_buffer;
    GLuint depth_render_buffer;
    GLuint frame_buffer;


-(void)render:(CADisplayLink*)displayLink;

@end

---

/* ----- GLView.mm ----- */

#import "GLView.h"

@implementation GLView

- (id)initWithFrame:(CGRect)frame

    self = [super initWithFrame:frame];
    if (self) 
        CAEAGLLayer* eaglLayer = (CAEAGLLayer*)self.layer;
        eaglLayer.opaque = YES;

        context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
        if(!context && ![EAGLContext setCurrentContext:context])
            [self release];
            return nil;
        

        int width = (int)frame.size.width;
        int height = (int)frame.size.height;

        glGenFramebuffers(1, &frame_buffer);
        glBindFramebuffer(GL_FRAMEBUFFER, frame_buffer);
        if(glIsFramebuffer(frame_buffer) == GL_FALSE)
            //NSLog(@"%i", frame_buffer);
            NSLog(@"frame_buffer is GL_FALSE!");
        

        glGenRenderbuffers(1, &color_render_buffer);
        glBindRenderbuffer(GL_RENDERBUFFER, color_render_buffer);
        [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:eaglLayer];

        if(glIsRenderbuffer(color_render_buffer) == GL_FALSE)
            NSLog(@"%i", color_render_buffer);
            NSLog(@"color_render_buffer is GL_FALSE");
        

        glGenRenderbuffers(1, &depth_render_buffer);
        glBindRenderbuffer(GL_RENDERBUFFER, depth_render_buffer);
        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);

        if(glIsRenderbuffer(depth_render_buffer) == GL_FALSE)
            NSLog(@"depth_render_buffer is GL_FALSE");
        


        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, color_render_buffer);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_render_buffer);

        if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
#ifdef DEBUG_LOG
            NSLog(@"Framebuffer is not complete!");
            exit(1);
#endif
        

        [[CADisplayLink displayLinkWithTarget:self selector:@selector(render:)] addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    
    return self;


+(Class)layerClass
    return [CAEAGLLayer class];


-(void)dealloc
    if([EAGLContext currentContext] == context)
        [EAGLContext setCurrentContext:nil];
    

    [context release];
    [super dealloc];


-(void)render:(CADisplayLink*)displayLink
    /* Rendering */

    [context presentRenderbuffer:GL_RENDERBUFFER];


@end

我总是得到“frame_buffer is GL_FALSE！”打印到控制台... frame_buffer 始终为 0（窗口系统默认帧缓冲区） 是否需要将任何设置添加到 plist 中？还是我错过了什么？

请帮忙。

【参考方案1】：

你永远不会调用 setCurrentContext: when context != nil. 变化：

if(!context && ![EAGLContext setCurrentContext:context])

收件人：

if(!context || ![EAGLContext setCurrentContext:context])

【讨论】：

短路评估就是这里发生的事情。您的代码首先检查 (!context)。上下文是正确的，因此执行第二个任期没有意义。此外，首先评估最左边的条件会在您的代码中产生维护风险 - 如果有人决定稍后在您的 if 语句中添加另一个子句怎么办？