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GLGETACTIVEUNIFORMBL(3G)                         OpenGL 3.3                         GLGETACTIVEUNIFORMBL(3G)



NAME
       glGetActiveUniformBlock - query information about an active uniform block

C SPECIFICATION
       void glGetActiveUniformBlockiv(GLuint program, GLuint uniformBlockIndex, GLenum pname, GLint params);

PARAMETERS
       program
           Specifies the name of a program containing the uniform block.

       uniformBlockIndex
           Specifies the index of the uniform block within program.

       pname
           Specifies the name of the parameter to query.

       params
           Specifies the address of a variable to receive the result of the query.

DESCRIPTION
       glGetActiveUniformBlockiv retrieves information about an active 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.


       uniformBlockIndex is an active uniform block index of program, and must be less than the value of
       GL_ACTIVE_UNIFORM_BLOCKS.

       Upon success, the uniform block parameter(s) specified by pname are returned in params. If an error
       occurs, nothing will be written to params.

       If pname is GL_UNIFORM_BLOCK_BINDING, then the index of the uniform buffer binding point last
       selected by the uniform block specified by uniformBlockIndex for program is returned. If no uniform
       block has been previously specified, zero is returned.

       If pname is GL_UNIFORM_BLOCK_DATA_SIZE, then the implementation-dependent minimum total buffer object
       size, in basic machine units, required to hold all active uniforms in the uniform block identified by
       uniformBlockIndex is returned. It is neither guaranteed nor expected that a given implementation will
       arrange uniform values as tightly packed in a buffer object. The exception to this is the std14_
       uniform block layout, which guarantees specific packing behavior and does not require the application
       to query for offsets and strides. In this case the minimum size may still be queried, even though it
       is determined in advance based only on the uniform block declaration.

       If pname is GL_UNIFORM_BLOCK_NAME_LENGTH, then the total length (including the nul terminator) of the
       name of the uniform block identified by uniformBlockIndex is returned.

       If pname is GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS, then the number of active uniforms in the uniform block
       identified by uniformBlockIndex is returned.

       If pname is GL_UNIFORM_BLOCK_ACTIVE_UNIFORM_INDICES, then a list of the active uniform indices for
       the uniform block identified by uniformBlockIndex is returned. The number of elements that will be
       written to params is the value of GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS for uniformBlockIndex.

       If pname is GL_UNIFORM_BLOCK_REFERENCED_BY_VERTEX_SHADER,
       GL_UNIFORM_BLOCK_REFERENCED_BY_GEOMETRY_SHADER, or GL_UNIFORM_BLOCK_REFERENCED_BY_FRAGMENT_SHADER,
       then a boolean value indicating whether the uniform block identified by uniformBlockIndex is
       referenced by the vertex, geometry, or fragment programming stages of program, respectively, is
       returned.

ERRORS
       GL_INVALID_VALUE is generated if uniformBlockIndex is greater than or equal to the value of
       GL_ACTIVE_UNIFORM_BLOCKS or is not the index of an active uniform block in program.


       GL_INVALID_ENUM is generated if pname is not one of the accepted tokens.


       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
       glGetActiveUniformBlockiv is available only if the GL version is 3.1 or greater.

SEE ALSO
       glGetActiveUniformBlockName(), glGetUniformBlockIndex(), glLinkProgram()


COPYRIGHT
       Copyright (C) 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/.



OpenGL 3.3                                       03/08/2011                         GLGETACTIVEUNIFORMBL(3G)