Framebuffer object: Difference between revisions

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The '''frame buffer object''' architecture (FBO) is an extension to [[OpenGL]] for doing flexible off-screen rendering, including rendering to a [[texture (computer graphics)|texture]]. By capturing images that would normally be drawn to the screen, it can be used to implement a large variety of image filters, and post-processing effects. The FBO is analogous to the '''render targets model''' in [[DirectX]]. It is used in OpenGL for its efficiency and ease of use. The use of FBOs doesn't suffer from the overhead associated with OpenGL drawing context switching, and has largely superseded the [[pbuffer]] and other methods involving context switches.

A frame buffer object is a method used in OpenGL to do off screen rendering and consequently allows render to texture.

== Uses ==

The FBO has two main uses: The post-processing of rendered images and composition between different scenes.

Some examples are:

# The rendered image is captured and subjected to [[Fragment Shaders]] or other manipulations. This allows for many of today's popular computer graphics effects to be carried out, including the addition of a blurring or bloom effect.

# Can be used to create views of other scenes, for example: a TV in a house showing the view from a secondary camera. A scene can be rendered through an FBO to a texture, then that texture can be applied to the surface of a TV. This is sometimes called "Render to Texture" or RTT.

== Advantages over other methods ==

=Links=

Methods involving the FBO are considered superior because:

* It is easier to set up than most other methods.

* Does not require context switching.

* Is more efficient because resources are shared within the same context.

* Is more flexible because all of [[depth buffer]], [[stencil buffer]], etc. can be acquired.

== Architecture ==

Framebuffer object techinal paper. [http://oss.sgi.com/projects/ogl-sample/registry/EXT/framebuffer_object.txt]

To use an FBO one simply creates an instance of it. Along with the FBO come several attachments. One can then attach these to a chosen receiver: either a [[Texture (computer graphics)|texture]], or a [[render buffer]].

For example:

Framebuffer object reference at openvidia.[http://openvidia.sourceforge.net/fbo.shtml]

* Create an FBO and bind it.

* Attach the color buffer (either as a RenderBuffer or a texture) to the FBO.

* Attach the depth buffer (either as a RenderBuffer or a texture) to the FBO.

* Bind the native window FrameBuffer (id=0)

* Render the texture to screen with a pixel shader, dependent on both the Color information and depth information.

== External links ==

{{compu-prog-stub}}

* [http://oss.sgi.com/projects/ogl-sample/registry/EXT/framebuffer_object.txt Framebuffer object technical paper] {{Webarchive|url=https://web.archive.org/web/20130502110335/http://oss.sgi.com/projects/ogl-sample/registry/EXT/framebuffer_object.txt |date=2013-05-02 }}

* [https://web.archive.org/web/20070108122530/http://openvidia.sourceforge.net/fbo.shtml Framebuffer object reference at openvidia]

* [http://www.songho.ca/opengl/gl_fbo.html Example code for Windows and Linux]

* [https://web.archive.org/web/20131101002803/http://www.opengl.org/wiki/GL_EXT_framebuffer_object EXT Framebuffer] (opengl.org)

[[Category:OpenGL]]