2010 Khronos Group
glGetUniformBlockIndex 3G
glGetUniformBlockIndex retrieve the index of a named uniform block

## C Specification

GLuint `glGetUniformBlockIndex` GLuint program const GLchar *uniformBlockName

## Parameters

program

  Specifies the name of a program containing the uniform block.

uniformBlockName

  Specifies the address an array of characters to containing the name of the uniform block whose index to retrieve.

## Description

`glGetUniformBlockIndex` retrieves the index of a uniform block within program.

program must be the name of a program object for which the command glLinkProgram must have been called in the past, although it is not required that glLinkProgram must have succeeded. The link could have failed because the number of active uniforms exceeded the limit.

uniformBlockName must contain a nul-terminated string specifying the name of the uniform block.

`glGetUniformBlockIndex` returns the uniform block index for the uniform block named uniformBlockName of program. If uniformBlockName does not identify an active uniform block of program, `glGetUniformBlockIndex` returns the special identifier, `GL_INVALID_INDEX`. Indices of the active uniform blocks of a program are assigned in consecutive order, beginning with zero.

## Errors

`GL_INVALID_OPERATION` is generated if program is not the name of a program object for which glLinkProgram has been called in the past.

## Notes

`glGetUniformBlockIndex` is available only if the GL version is 3.1 or greater.

## See Also

glGetActiveUniformBlockName, glGetActiveUniformBlock, glLinkProgram

## Copyright

Copyright 2010 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/.