GLAPI/glGetActiveUniformBlock

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glGetActiveUniformBlock
Core in version 4.5
Core since version 3.1

glGetActiveUniformBlock: query information about an active uniform block

Function Definition

 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.

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 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_TESS_CONTROL_SHADER, GL_UNIFORM_BLOCK_REFERENCED_BY_TESS_EVALUATION_SHADER, GL_UNIFORM_BLOCK_REFERENCED_BY_GEOMETRY_SHADER, GL_UNIFORM_BLOCK_REFERENCED_BY_FRAGMENT_SHADER, or GL_UNIFORM_BLOCK_REFERENCED_BY_COMPUTE_SHADER then a boolean value indicating whether the uniform block identified by uniformBlockIndex​ is referenced by the vertex, tessellation control, tessellation evaluation, geometry, fragment or compute 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.

GL_UNIFORM_BLOCK_REFERENCED_BY_COMPUTE_SHADER is accepted only if the GL version is 4.3 or greater.

Associated Gets

glGetProgram with GL_ACTIVE_UNIFORM_BLOCKS

glGetProgramInterface with GL_UNIFORM_BLOCK and GL_ACTIVE_RESOURCES

glGetUniformBlockIndex

glGetProgramResourceIndex with GL_UNIFORM_BLOCK

See Also

glGetActiveUniformBlockName, glGetProgramResource, glGetProgramResourceName

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/.