GLREADFRAMEBUFFER

GLREADFRAMEBUFFER is a constant used in OpenGL programming. It represents the framebuffer that is currently bound for reading operations. When performing operations that involve reading pixel data from the framebuffer, such as capturing screenshots or performing read pixels, this constant is used to specify which framebuffer the data should be read from.

In OpenGL, a framebuffer object is a collection of image buffers that can be used as rendering targets. Multiple framebuffers can exist concurrently, and the application can bind different framebuffers to different contexts or operations. The GL_READ_FRAMEBUFFER constant is used in functions like glBindFramebuffer and glFramebufferTexture2D to associate a specific framebuffer object with the read target.

When you call glReadPixels, for example, it reads pixels from the framebuffer currently bound to GL_READ_FRAMEBUFFER. If no framebuffer object is explicitly bound to the read target, it defaults to the window-system-provided framebuffer, often referred to as the "default framebuffer" or "back buffer." Understanding the distinction between the read framebuffer and the draw framebuffer is crucial for advanced rendering techniques like ping-ponging between framebuffers or implementing effects that require reading from one buffer while rendering to another.