Difference between revisions of "GLAPI/glReadBuffer"

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== Description ==
 
== Description ==
  
'''glReadBuffer''' specifies a color buffer as the source for subsequent {{apifunc|glReadPixels}}, {{apifunc|glCopyTexImage1D}}, {{apifunc|glCopyTexImage2D}}, {{apifunc|glCopyTexSubImage1D}}, {{apifunc|glCopyTexSubImage2D}}, and {{apifunc|glCopyTexSubImage3D}} commands. {{param|mode}} accepts one of twelve or more predefined values. In a fully configured system, {{enum|GL_FRONT}}, {{enum|GL_LEFT}}, and {{enum|GL_FRONT_LEFT}} all name the front left buffer, {{enum|GL_FRONT_RIGHT}} and {{enum|GL_RIGHT}} name the front right buffer, and {{enum|GL_BACK_LEFT}} and {{enum|GL_BACK}} name the back left buffer. Further more, the constants {{enum|GL_COLOR_ATTACHMENT''i''}} may be used to indicate the ''i''<sup>th</sup> color attachment where ''i'' ranges from zero to the value of {{enum|GL_MAX_COLOR_ATTACHMENTS}} minus one.
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'''glReadBuffer''' specifies which color buffer within the current bound {{enum|GL_READ_FRAMEBUFFER}} will be used as the source for pixel reading commands. These commands include: {{apifunc|glBlitFramebuffer}}, {{apifunc|glReadPixels}}, {{apifunc|glCopyTexImage1D}}, {{apifunc|glCopyTexImage2D}}, {{apifunc|glCopyTexSubImage1D}}, {{apifunc|glCopyTexSubImage2D}}, and {{apifunc|glCopyTexSubImage3D}}.
  
Nonstereo double-buffered configurations have only a front left and a back left buffer. Single-buffered configurations have a front left and a front right buffer if stereo, and only a front left buffer if nonstereo. It is an error to specify a nonexistent buffer to '''glReadBuffer'''.
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{{param|mode}} accepts one of twelve or more predefined values. If the [[default framebuffer]] (the zero [[framebuffer object]])is bound to {{enum|GL_READ_FRAMEBUFFER}}, then the following enumerators can be used: {{enum|GL_FRONT}}, {{enum|GL_LEFT}}, and {{enum|GL_FRONT_LEFT}} all name the front left buffer, {{enum|GL_FRONT_RIGHT}} and {{enum|GL_RIGHT}} name the front right buffer, and {{enum|GL_BACK_LEFT}} and {{enum|GL_BACK}} name the back left buffer. Nonstereo double-buffered configurations have only a front left and a back left buffer. Single-buffered configurations have a front left and a front right buffer if stereo, and only a front left buffer if nonstereo.
  
{{param|mode}} is initially {{enum|GL_FRONT}} in single-buffered configurations and {{enum|GL_BACK}} in double-buffered configurations.
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If a non-zero framebuffer object is bound, then the constants {{enum|GL_COLOR_ATTACHMENT''i''}} may be used to indicate the ''i''<sup>th</sup> color attachment, where ''i'' ranges from zero to the value of {{enum|GL_MAX_COLOR_ATTACHMENTS}} minus one.
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It is an error to specify a nonexistent buffer to '''glReadBuffer'''.
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For the default framebuffer, {{param|mode}} is initially {{enum|GL_FRONT}} in single-buffered configurations and {{enum|GL_BACK}} in double-buffered configurations. For framebuffer objects, the default read buffer is {{enum|GL_COLOR_ATTACHMENT0}}.
  
 
== Errors ==
 
== Errors ==

Revision as of 13:05, 15 July 2012

glReadBuffer
Core in version 4.5
Core since version 1.0

glReadBuffer: select a color buffer source for pixels

Function Definition

 void glReadBuffer(GLenum mode​);
mode
Specifies a color buffer. Accepted values are GL_FRONT_LEFT, GL_FRONT_RIGHT, GL_BACK_LEFT, GL_BACK_RIGHT, GL_FRONT, GL_BACK, GL_LEFT, GL_RIGHT, and the constants GL_COLOR_ATTACHMENTi.

Description

glReadBuffer specifies which color buffer within the current bound GL_READ_FRAMEBUFFER will be used as the source for pixel reading commands. These commands include: glBlitFramebuffer, glReadPixels, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, and glCopyTexSubImage3D.

mode​ accepts one of twelve or more predefined values. If the default framebuffer (the zero framebuffer object)is bound to GL_READ_FRAMEBUFFER, then the following enumerators can be used: GL_FRONT, GL_LEFT, and GL_FRONT_LEFT all name the front left buffer, GL_FRONT_RIGHT and GL_RIGHT name the front right buffer, and GL_BACK_LEFT and GL_BACK name the back left buffer. Nonstereo double-buffered configurations have only a front left and a back left buffer. Single-buffered configurations have a front left and a front right buffer if stereo, and only a front left buffer if nonstereo.

If a non-zero framebuffer object is bound, then the constants GL_COLOR_ATTACHMENTi may be used to indicate the ith color attachment, where i ranges from zero to the value of GL_MAX_COLOR_ATTACHMENTS minus one.

It is an error to specify a nonexistent buffer to glReadBuffer.

For the default framebuffer, mode​ is initially GL_FRONT in single-buffered configurations and GL_BACK in double-buffered configurations. For framebuffer objects, the default read buffer is GL_COLOR_ATTACHMENT0.

Errors

GL_INVALID_ENUM is generated if mode​ is not one of the twelve (or more) accepted values.

GL_INVALID_OPERATION is generated if mode​ specifies a buffer that does not exist.

Associated Gets

glGet with argument GL_READ_BUFFER

See Also

glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, glCopyTexSubImage3D, glDrawBuffer, glReadPixels

Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2011 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.