glReadBuffer — select a color buffer source for pixels
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
GL_AUX
i,
where i is between 0 and the value of GL_AUX_BUFFERS
minus 1.
glReadBuffer
specifies a color buffer as the source for subsequent
glReadPixels, glCopyTexImage1D, glCopyTexImage2D,
glCopyTexSubImage1D, glCopyTexSubImage2D,
glCopyTexSubImage3D, and
glCopyPixels commands.
mode
accepts one of twelve or more predefined values.
(GL_AUX0
through GL_AUX3
are always defined.)
In a fully configured system,
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.
It is an error to specify a nonexistent buffer to glReadBuffer
.
mode
is initially GL_FRONT
in single-buffered configurations
and GL_BACK
in double-buffered configurations.
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.
GL_INVALID_OPERATION
is generated if glReadBuffer
is executed between the execution of glBegin
and the corresponding execution of glEnd.
glCopyPixels, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, glCopyTexSubImage3D, glDrawBuffer, glReadPixels
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