glDrawBuffers - OpenGL ES 3 Reference Pages

## Name

glDrawBuffers — Specifies a list of color buffers to be drawn into

## C Specification

`void glDrawBuffers(` | GLsizei n,
| const GLenum *bufs`)`;

## Parameters

`n`

  Specifies the number of buffers in `bufs`.

`bufs`

  Points to an array of symbolic constants specifying the buffers into which fragment colors or data values will be written.

## Description

`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` must be one of the following, depending on whether GL is bound to the default framebuffer or not:

`GL_NONE`

  The fragment shader output value is not written into any color buffer.

`GL_BACK`

  The fragment shader output value is written into the back color buffer.

`GL_COLOR_ATTACHMENT` n

  The fragment shader output value is written into the nth color attachment of the current framebuffer. n may range from zero 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`.

## Notes

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`.

## Errors

`GL_INVALID_ENUM` is generated if one of the values in `bufs` is not an accepted value.

`GL_INVALID_OPERATION` is generated if the GL is bound to the default framebuffer and `n` is not 1, or if the value in `bufs` is one of the `GL_COLOR_ATTACHMENT`n tokens.

`GL_INVALID_OPERATION` is generated if the GL is bound to a framebuffer object and the ith buffer listed in `bufs` is anything other than `GL_NONE` or `GL_COLOR_ATTACHMENTS`i.

`GL_INVALID_VALUE` is generated if `n` is less than 0 or greater than `GL_MAX_DRAW_BUFFERS`.

## Associated Gets

glGet with argument `GL_MAX_DRAW_BUFFERS`

glGet with argument `GL_DRAW_BUFFER`i where i indicates the number of the draw buffer whose value is to be queried.

## API Version Support

| OpenGL ES API Version
--- | ---
Function Name | 2.0 | 3.0
glDrawBuffers | - | ✔

## See Also

glReadBuffer

## Copyright

Copyright © 2003-2005 3Dlabs Inc. Ltd. Copyright © 2010-2014 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/.