Question

我很难使用OpenGL函数glBlitFramebuffer。在文档中，它表示它支持blitting颜色和深度缓冲区。但是，在实践中却没有。我在Macbook AIR 13英寸，Intel HD Graphics 5000 1536 MB。

我需要从http://ake.in.th/2013/04/02/offscreening-and-multisampling-with-opengl/

进行多重采样

我的多重采样级别是4（AA_LEVEL = 4），我的OpenGL版本是：3.2核心配置文件。这就是我在做的事情：

创建多样本AA帧缓冲区。

glGenFramebuffers( 1, &_offscreenBufferHandle );
glBindFramebuffer( GL_FRAMEBUFFER, _offscreenBufferHandle );

glGenRenderbuffers(1, &_depthRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderbuffer);
glRenderbufferStorageMultisample(GL_RENDERBUFFER, AA_LEVEL, GL_DEPTH_COMPONENT16, srcWidth_, srcHeight_);
glBindRenderbuffer(GL_RENDERBUFFER, 0);

glGenRenderbuffers(1, &_aaColorbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _aaColorbuffer);
glRenderbufferStorageMultisample(GL_RENDERBUFFER, AA_LEVEL, GL_RGBA, srcWidth_, srcHeight_);
glBindRenderbuffer(GL_RENDERBUFFER, 0);

创建目标帧缓冲区

glGenFramebuffers( 1, &_outputBufferHandle );
glBindFramebuffer( GL_FRAMEBUFFER, _outputBufferHandle );

glGenRenderbuffers(1, &_outputColorbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _outputColorbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA, srcWidth_, srcHeight_);
glBindRenderbuffer(GL_RENDERBUFFER, 0);

glGenRenderbuffers(1, &_outputDepthbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _outputDepthbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, srcWidth_, srcHeight_);
glBindRenderbuffer(GL_RENDERBUFFER, 0);

使用颜色和深度缓冲区绘制内容

glBindFramebuffer( GL_DRAW_FRAMEBUFFER, _offscreenBufferHandle );
glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _aaColorbuffer);
glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderbuffer);  
//next 
DrawStuff();

将多样本AA帧缓冲区blit到目标帧缓冲区中。

glBindFramebuffer( GL_READ_FRAMEBUFFER, _offscreenBufferHandle );
glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _aaColorbuffer);
glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderbuffer);

 glBindFramebuffer( GL_DRAW_FRAMEBUFFER, _outputBufferHandle );
 glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _outputColorbuffer);
 glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _outputDepthbuffer);

 if( glCheckFramebufferStatus(GL_READ_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE &&
glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE ) {
    //do blitting here
    glBlitFramebuffer(0, 0, srcWidth_, srcHeight_, 0, 0, srcWidth_, srcHeight_, GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT, GL_NEAREST);
 }

从目标帧缓冲区中读取像素并进行一些后期处理

//then blit it to pixels buffer
glBindFramebuffer(GL_READ_FRAMEBUFFER, _outputBufferHandle);
glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _outputColorbuffer);
glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _outputDepthbuffer);
readParam("temp");

GLenum framebufferStatus = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if( framebufferStatus == GL_FRAMEBUFFER_COMPLETE ) {
    glReadBuffer(GL_COLOR_ATTACHMENT0);
    //getGLErr("GL_COLOR_ATTACHMENT0");
    glReadPixels(0, 0, srcWidth_, srcHeight_, GL_BGR, GL_UNSIGNED_BYTE, pixels);
}

然而结果只有颜色缓冲液成功印迹，没有深度缓冲。

如果我禁用多重采样，通过更改我的AA_LEVEL = 0，并替换删除步骤4，用以下代码替换步骤5直接从_offscreenBufferHandle读取，结果看起来正确。

glBindFramebuffer(GL_READ_FRAMEBUFFER, _offscreenBufferHandle);
glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _aaColorbuffer);
glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderbuffer);
GLenum framebufferStatus = glCheckFramebufferStatus(GL_READ_FRAMEBUFFER);
if( framebufferStatus == GL_FRAMEBUFFER_COMPLETE ) {
    glReadPixels(0, 0, srcWidth_, srcHeight_, GL_BGR, GL_UNSIGNED_BYTE, pixels);
}

很多帖子都指向类似的问题，我很困惑这是一个图形卡问题，还是我一直在做的事情是错误的。

https://gamedev.stackexchange.com/questions/68290/fbo-blit-depth-buffer-to-screen

https://www.opengl.org/discussion_boards/showthread.php/176317-Framebuffer-not-bliting-depth-buffer

在这些文章中，这意味着我需要绘制纹理四边形，而不是从读取缓冲区到绘制缓冲区执行blit。那太麻烦了。

OpenGL glBlitFramebuffer不会正确地对颜色和深度缓冲区进行blit。结果从glReadPixel验证

0 个答案: