What Is an OpenGL® Framebuffer?

Alex Newth

The Open Graphics Library® (OpenGL®) framebuffer is a coding object that simplifies buffer coding for rendering. A primary use for the OpenGL® framebuffer is adding graphic effects to an image, which is usually a feature associated with graphic design programs. Another use of the OpenGL® framebuffer is to add texture to an image, such as static or blurring. While effects and textures may look good on their own, the framebuffer is relatively useless unless there is an image to which one can bind the effects or textures; otherwise, nothing will show up. When the framebuffer is used, it combines several other buffers, which makes pooling the graphic resources more efficient than if the buffers were used separately.

One use for the OpenGL® framebuffer is adding graphic effects to a 3D image.
One use for the OpenGL® framebuffer is adding graphic effects to a 3D image.

Common graphic design programs have a list of special effects that can be added to an image, but performing the same procedure in OpenGL® is rather complex. When the OpenGL® framebuffer is used, it places an image through many shaders that are able to create per-pixel effects. This means complex effects can be applied to the OpenGL® image, making it easier to add effects and for those effects to be visually consistent.

There are many textures in the physical world — nearly every object has some visually distinct texture. If an OpenGL® project is supposed to emulate reality, then being able to apply a texture is important. There are a few methods for adding a texture in this program, but the OpenGL® framebuffer is one of the easier methods. By using this object, a texture can be applied to an area or graphic object via a small amount of code.

One problem with the OpenGL® framebuffer is that it cannot work by itself; there must be another image accompanying the effects or nothing will appear onscreen. The effects and textures are applied to an image, so this limitation rarely presents itself. When a user is creating a framebuffer object, it is important that the framebuffer and image are the same size or there will be areas without effects or textures. The two also must be bound together or the image may not be correct during operation.

Another reason to use the OpenGL® framebuffer is that it uses several other buffers simultaneously. Not only does this make coordinating the buffers much easier, but fewer resources are required to run the framebuffer when compared to using the other buffers separately. The buffers used are the color, index, depth, stencil and render buffers.

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