glDrawBuffers — Specifies a list of color buffers to be drawn into
void glDrawBuffers( | GLsizei n, |
const GLenum *bufs); |
nSpecifies the number of buffers in
bufs.
bufsPoints to an array of symbolic constants specifying the buffers into which fragment colors or data values will be written.
glDrawBuffers defines an array of
buffers into which outputs from the fragment shader data will
be written. If a fragment shader writes a value
to one or more user defined output
variables, then the value of each variable will be written into the
buffer specified at a location within bufs
corresponding to the location assigned to that user defined output.
The draw buffer used for user defined outputs assigned to locations
greater than or equal to n is implicitly set
to GL_NONE and any data written to such an output
is discarded.
The symbolic constants contained in
bufs may be any of the following:
GL_NONEThe fragment shader output value is not written into any color buffer.
GL_FRONT_LEFTThe fragment shader output value is written into the front left color buffer.
GL_FRONT_RIGHTThe fragment shader output value is written into the front right color buffer.
GL_BACK_LEFTThe fragment shader output value is written into the back left color buffer.
GL_BACK_RIGHTThe fragment shader output value is written into the back right color buffer.
GL_COLOR_ATTACHMENTnThe fragment shader output value is written into the
nth color attachment of the current framebuffer.
n may range from 0 to the value of
GL_MAX_COLOR_ATTACHMENTS.
Except for GL_NONE, the preceding
symbolic constants may not appear more than once in
bufs. The maximum number of draw buffers
supported is implementation dependent and can be queried by
calling
glGet
with the argument GL_MAX_DRAW_BUFFERS.
The symbolic constants GL_FRONT,
GL_BACK, GL_LEFT,
GL_RIGHT, and
GL_FRONT_AND_BACK are not allowed in the
bufs array since they may refer to
multiple buffers.
If a fragment shader does not write to a user defined output variable,
the values of the fragment
colors following shader execution are undefined. For each
fragment generated in this situation, a different value may be
written into each of the buffers specified by
bufs.
GL_INVALID_ENUM is generated if one of the
values in bufs is not an accepted
value.
GL_INVALID_ENUM is generated if the GL is bound
to the default framebuffer and one or more of the values in
bufs is one of the GL_COLOR_ATTACHMENTn
tokens.
GL_INVALID_ENUM is generated if the GL is bound
to a framebuffer object and one or more of the values in bufs
is anything other than GL_NONE or one of the
GL_COLOR_ATTACHMENTn tokens.
GL_INVALID_ENUM is generated if
n is less than 0.
GL_INVALID_OPERATION is generated if a
symbolic constant other than GL_NONE
appears more than once in bufs.
GL_INVALID_OPERATION is generated if any of
the entries in bufs (other than
GL_NONE ) indicates a color buffer that
does not exist in the current GL context.
GL_INVALID_VALUE is generated if
n is greater than
GL_MAX_DRAW_BUFFERS.
glGet
with argument GL_MAX_DRAW_BUFFERS
glGet
with argument GL_DRAW_BUFFERi where
i indicates the number of the draw buffer
whose value is to be queried
Copyright © 2003-2005 3Dlabs Inc. Ltd. 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/.