glBindFramebuffer — bind a named framebuffer object
Specifies the target to which the framebuffer object is bound.
The symbolic constant must be
Specifies the name of a framebuffer object.
glBindFramebuffer lets you create or use a named framebuffer object. Calling
target set to
framebuffer set to the name
of the new framebuffer object binds the framebuffer object name.
When a framebuffer object is bound, the previous binding
is automatically broken.
Framebuffer object names are unsigned integers. The value zero is reserved to represent the default framebuffer provided by the windowing system. Framebuffer object names and the corresponding framebuffer object contents are local to the shared object space of the current GL rendering context.
You may use glGenFramebuffers to generate a set of new framebuffer object names.
The state of a framebuffer object immediately after it is first bound is
three attachment points (
GL_STENCIL_ATTACHMENT) each with
GL_NONE as the object type.
While a non-zero framebuffer object name is bound, GL operations on
GL_FRAMEBUFFER affect the bound framebuffer
object, and queries of target
GL_FRAMEBUFFER or of
framebuffer details such as
return state from the bound framebuffer object. While framebuffer object
name zero is bound, as in the initial state, attempts to modify or query
state on target
GL_FRAMEBUFFER generates an
While a non-zero framebuffer object name is bound, all rendering to the framebuffer (with glDrawArrays and glDrawElements) and reading from the framebuffer (with glReadPixels, glCopyTexImage2D, or glCopyTexSubImage2D) use the images attached to the application-created framebuffer object rather than the default window-system-provided framebuffer.
Application created framebuffer objects (i.e. those with a non-zero name)
differ from the default window-system-provided framebuffer in a few
important ways. First, they have modifiable attachment points for
a color buffer, a depth buffer, and a stencil buffer to which framebuffer
attachable images may be attached and detached. Second, the size and format of the
attached images are controlled entirely within the GL and are not
affected by window-system events, such as pixel format selection,
window resizes, and display mode changes. Third, when rendering to or
reading from an application created framebuffer object, the pixel
ownership test always succeeds (i.e. they own all their pixels). Fourth,
there are no visible color buffer bitplanes, only a single "off-screen"
color image attachment, so there is no sense of front and back buffers
or swapping. Finally, there is no multisample buffer, so the value of
the implementation-dependent state variables
are both zero for application created framebuffer objects.
A framebuffer object binding created with
glBindFramebuffer remains active until a different
framebuffer object name is bound, or until the bound framebuffer object is
deleted with glDeleteFramebuffers.
Queries of implementation-dependent pixel depths and related state are
derived from the currently bound framebuffer object. These include
glGet with argument
// fbo_width and fbo_height are the desired width and height of the FBO. // For Opengl <= 4.4 or if the GL_ARB_texture_non_power_of_two extension // is present, fbo_width and fbo_height can be values other than 2^n for // some integer n. // Build the texture that will serve as the color attachment for the framebuffer. GLuint texture_map; glGenTextures(1, &texture_map); glBindTexture(GL_TEXTURE_2D, texture_map); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, fbo_width, fbo_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); glBindTexture(GL_TEXTURE_2D, 0); // Build the texture that will serve as the depth attachment for the framebuffer. GLuint depth_texture; glGenTextures(1, &depth_texture); glBindTexture(GL_TEXTURE_2D, depth_texture); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, fbo_width, fbo_height, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, NULL); glBindTexture(GL_TEXTURE_2D, 0); // Build the framebuffer. GLuint framebuffer; glGenFramebuffers(1, &framebuffer); glBindFramebuffer(GL_FRAMEBUFFER, (GLuint)framebuffer); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture_map, 0); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depth_texture, 0); GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER); if (status != GL_FRAMEBUFFER_COMPLETE) // Error glBindFramebuffer(GL_FRAMEBUFFER, 0);
Copyright © 2008 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.