glGetActiveUniformBlock — query information about an active uniform block
void glGetActiveUniformBlockiv( | GLuint | program, |
GLuint | uniformBlockIndex, | |
GLenum | pname, | |
GLint * | params) ; |
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.
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 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.
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.
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.
Copyright © 2010-2013 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/.