framebufferRenderbuffer

A framebuffer renderbuffer is a type of object used in graphics programming, particularly within the OpenGL API. It represents a memory buffer that stores image data. Unlike a texture, a renderbuffer is not directly accessible as a texture by the shader pipeline. Instead, its primary purpose is to serve as a destination for rendering operations.

When rendering to a framebuffer object (FBO), applications typically attach one or more renderbuffers to specific attachment points, such as color, depth, or stencil. The GPU then writes the results of rendering commands, like drawing polygons or clearing the screen, directly into these attached renderbuffers. This allows for offscreen rendering, where the output of a rendering pass is not displayed on the screen but is instead stored for later use.

The internal format of a renderbuffer can be specified, influencing the data type and precision of the stored pixels. Common formats include depth components, stencil indices, or various color representations. Because renderbuffers are optimized for writing by the GPU, they can offer performance advantages over textures when the data will not be sampled as a texture in the same rendering pass.

The content of a renderbuffer can be read back by the CPU, though this can be a relatively slow operation. Alternatively, a renderbuffer can be converted into a texture, making its contents accessible for sampling by shaders in subsequent rendering steps. This conversion is often performed efficiently by the graphics hardware. Framebuffer renderbuffers are essential for techniques like deferred rendering, post-processing effects, and rendering to textures.