glGetActiveUniformBlock — query information about an active uniform block
Specifies the name of a program containing the uniform block.
Specifies the index of the uniform block within
Specifies the name of the parameter to query.
Specifies the address of a variable to receive the result of the query.
glGetActiveUniformBlockiv retrieves information about an active uniform block within
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
Upon success, the uniform block parameter(s) specified by
pname are returned in
params. If an error
occurs, nothing will be written to
GL_UNIFORM_BLOCK_BINDING, then the index of the uniform buffer binding point
last selected by the uniform block specified by
program is returned. If
no uniform block has been previously specified, zero is returned.
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
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 std140 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.
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.
GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS, then the number of active uniforms in the uniform
block identified by
uniformBlockIndex is returned.
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_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.
GL_INVALID_VALUE is generated if
uniformBlockIndex is greater than or equal to the value
GL_ACTIVE_UNIFORM_BLOCKS or is not the index of an active uniform block in
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.
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