Copy Data from Backbuffer to Frontbuffer

Question

I've googled a bit about this subject and everyone seems to believe on other webpages that to do such thing as copying the contents from the Backbuffer to the Frontbuffer, without calling SwapBuffers, is not possible.

There's some kind of workarround as creating an auxiliar extra buffer (like pBuffer), render to it and copy the contents into a texture and then display the texture.

But I'm wondering if there is really no chance to Render on the Backbuffer of Opengl, and copy contents to the frontbuffer. I want to achieve this because between 2 calls of SwapBuffers, many of my rendered scene remains the same, and only a small portion (rectangle) of it has been changed, so I would like to avoid RENDERING the other 90% of the scene unnecessarily everytime.

Pixel Buffer Objects seem to help us copying pixels from FrameBuffer to a Pixel Buffer Object, using Direct Memory Acess. My machine doesn't support it, but even if it did, we're once again allocating an extra buffer.

So is there really Absolutely no way to copy the contents or part of the contents between Back and the Front buffers of my window?

Yakov Galka Yakov Galka · Accepted Answer · 2018-01-12T03:25:23

You can do it since OpenGL 3.0 (or earlier versions through extensions when available) as follows:

glReadBuffer(GL_BACK);
glDrawBuffer(GL_FRONT);
glBlitFramebuffer(srcX0, srcY0, srcX1, srcY1,
    dstX0, dstY0, dstX1, dstY1, GL_COLOR_BUFFER_BIT, GL_NEAREST);

Copy Data from Backbuffer to Frontbuffer

2 Answers