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Asked: 2026-05-28T19:07:46+00:00

To clarify, when I say ‘default framebuffer’ I mean the one provided by the

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To clarify, when I say ‘default framebuffer’ I mean the one provided by the windowing system and what ends up on your monitor.

To improve my rendering speeds for a CAD app, I’ve managed to separate out the 3D elements from the Qt-handled 2D ones, and they now each render into their own FBO. When the time comes to get them onto the screen, I blit the 3D FBO onto the default FB, and then I want to blend my 2D FBO on top of it.

I’ve gotten to the blitting part fine, but I can’t see how to blend my 2D FBO onto it? Both FBOs are identical in size and format, and they are both the same as the default FB.

I’m sure it’s a simple operation, but I can’t find anything on the net – presumably I’m missing the right term for what I am trying to do. Although I’m using Qt, I can use native OpenGL commands without issue.

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1 Answer

  1. Editorial Team

    A blit operation is ultimately a pixel copy operation. If you want to layer one image on top of another, you can’t blit it. You must instead render a full-screen quad as a texture and use the proper blending parameters for your blending operation.

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