# GLAPI/glGetActiveUniforms

Core in version | 4.4 | |
---|---|---|

Core since version | 2.0 |

**glGetActiveUniforms:** Returns information about several active uniform variables for the specified program object

## Contents

## Function Definition

voidglGetActiveUniformsiv(GLuint program, GLsizei uniformCount, const GLuint *uniformIndices, GLenum pname, GLint *params);

- program
- Specifies the program object to be queried.
- uniformCount
- Specifies both the number of elements in the array of indices uniformIndices and the number of parameters written to params upon successful return.
- uniformIndices
- Specifies the address of an array of uniformCount integers containing the indices of uniforms within program whose parameter pname pname.
- pname
- Specifies the property of the each uniform in uniformIndices that should be written into the corresponding element of params.
- params
- Specifies the address of an array of uniformCount integers which are to receive the value of pname for each uniform in uniformIndices.

## Description

**glGetActiveUniformsiv** queries the value of the parameter named pname for each of the uniforms within program whose indices are specified in the array of uniformCount unsigned integers uniformIndices. Upon success, the value of the parameter for each uniform is written into the corresponding entry in the array whose address is given in params. If an error is generated, nothing is written into params.

If pname is GL_UNIFORM_TYPE, then an array identifying the types of uniforms specified by the corresponding array of uniformIndices is returned. The returned types can be any of the values from the following table:

Returned Symbolic Contant |
Shader Uniform Type |
---|---|

GL_FLOAT | float |

GL_FLOAT_VEC2 | vec2 |

GL_FLOAT_VEC3 | vec3 |

GL_FLOAT_VEC4 | vec4 |

GL_DOUBLE | double |

GL_DOUBLE_VEC2 | dvec2 |

GL_DOUBLE_VEC3 | dvec3 |

GL_DOUBLE_VEC4 | dvec4 |

GL_INT | int |

GL_INT_VEC2 | ivec2 |

GL_INT_VEC3 | ivec3 |

GL_INT_VEC4 | ivec4 |

GL_UNSIGNED_INT | unsigned int |

GL_UNSIGNED_INT_VEC2 | uvec2 |

GL_UNSIGNED_INT_VEC3 | uvec3 |

GL_UNSIGNED_INT_VEC4 | uvec4 |

GL_BOOL | bool |

GL_BOOL_VEC2 | bvec2 |

GL_BOOL_VEC3 | bvec3 |

GL_BOOL_VEC4 | bvec4 |

GL_FLOAT_MAT2 | mat2 |

GL_FLOAT_MAT3 | mat3 |

GL_FLOAT_MAT4 | mat4 |

GL_FLOAT_MAT2x3 | mat2x3 |

GL_FLOAT_MAT2x4 | mat2x4 |

GL_FLOAT_MAT3x2 | mat3x2 |

GL_FLOAT_MAT3x4 | mat3x4 |

GL_FLOAT_MAT4x2 | mat4x2 |

GL_FLOAT_MAT4x3 | mat4x3 |

GL_DOUBLE_MAT2 | dmat2 |

GL_DOUBLE_MAT3 | dmat3 |

GL_DOUBLE_MAT4 | dmat4 |

GL_DOUBLE_MAT2x3 | dmat2x3 |

GL_DOUBLE_MAT2x4 | dmat2x4 |

GL_DOUBLE_MAT3x2 | dmat3x2 |

GL_DOUBLE_MAT3x4 | dmat3x4 |

GL_DOUBLE_MAT4x2 | dmat4x2 |

GL_DOUBLE_MAT4x3 | dmat4x3 |

GL_SAMPLER_1D | sampler1D |

GL_SAMPLER_2D | sampler2D |

GL_SAMPLER_3D | sampler3D |

GL_SAMPLER_CUBE | samplerCube |

GL_SAMPLER_1D_SHADOW | sampler1DShadow |

GL_SAMPLER_2D_SHADOW | sampler2DShadow |

GL_SAMPLER_1D_ARRAY | sampler1DArray |

GL_SAMPLER_2D_ARRAY | sampler2DArray |

GL_SAMPLER_1D_ARRAY_SHADOW | sampler1DArrayShadow |

GL_SAMPLER_2D_ARRAY_SHADOW | sampler2DArrayShadow |

GL_SAMPLER_2D_MULTISAMPLE | sampler2DMS |

GL_SAMPLER_2D_MULTISAMPLE_ARRAY | sampler2DMSArray |

GL_SAMPLER_CUBE_SHADOW | samplerCubeShadow |

GL_SAMPLER_BUFFER | samplerBuffer |

GL_SAMPLER_2D_RECT | sampler2DRect |

GL_SAMPLER_2D_RECT_SHADOW | sampler2DRectShadow |

GL_INT_SAMPLER_1D | isampler1D |

GL_INT_SAMPLER_2D | isampler2D |

GL_INT_SAMPLER_3D | isampler3D |

GL_INT_SAMPLER_CUBE | isamplerCube |

GL_INT_SAMPLER_1D_ARRAY | isampler1DArray |

GL_INT_SAMPLER_2D_ARRAY | isampler2DArray |

GL_INT_SAMPLER_2D_MULTISAMPLE | isampler2DMS |

GL_INT_SAMPLER_2D_MULTISAMPLE_ARRAY | isampler2DMSArray |

GL_INT_SAMPLER_BUFFER | isamplerBuffer |

GL_INT_SAMPLER_2D_RECT | isampler2DRect |

GL_UNSIGNED_INT_SAMPLER_1D | usampler1D |

GL_UNSIGNED_INT_SAMPLER_2D | usampler2D |

GL_UNSIGNED_INT_SAMPLER_3D | usampler3D |

GL_UNSIGNED_INT_SAMPLER_CUBE | usamplerCube |

GL_UNSIGNED_INT_SAMPLER_1D_ARRAY | usampler2DArray |

GL_UNSIGNED_INT_SAMPLER_2D_ARRAY | usampler2DArray |

GL_UNSIGNED_INT_SAMPLER_2D_MULTISAMPLE | usampler2DMS |

GL_UNSIGNED_INT_SAMPLER_2D_MULTISAMPLE_ARRAY | usampler2DMSArray |

GL_UNSIGNED_INT_SAMPLER_BUFFER | usamplerBuffer |

GL_UNSIGNED_INT_SAMPLER_2D_RECT | usampler2DRect |

If pname is GL_UNIFORM_SIZE, then an array identifying the size of the uniforms specified by the corresponding array of uniformIndices is returned. The sizes returned are in units of the type returned by a query of GL_UNIFORM_TYPE. For active uniforms that are arrays, the size is the number of active elements in the array; for all other uniforms, the size is one.

If pname is GL_UNIFORM_NAME_LENGTH, then an array identifying the length, including the terminating null character, of the uniform name strings specified by the corresponding array of uniformIndices is returned.

If pname is GL_UNIFORM_BLOCK_INDEX, then an array identifying the the uniform block index of each of the uniforms specified by the corresponding array of uniformIndices is returned. The uniform block index of a uniform associated with the default uniform block is -1.

If pname is GL_UNIFORM_OFFSET, then an array of uniform buffer offsets is returned. For uniforms in a named uniform block, the returned value will be its offset, in basic machine units, relative to the beginning of the uniform block in the buffer object data store. For atomic counter uniforms, the returned value will be its offset relative to the beginning of its active atomic counter buffer. For all other uniforms, -1 will be returned.

If pname is GL_UNIFORM_ARRAY_STRIDE, then an array identifying the stride between elements of each of the uniforms specified by the corresponding array of uniformIndices is returned. For uniforms in named uniform blocks and for uniforms declared as atomic counters, the stride is the difference, in basic machine units, of consecutive elements in an array, or zero for uniforms not declared as an array. For all other uniforms, a stride of -1 will be returned.

If pname is GL_UNIFORM_MATRIX_STRIDE, then an array identifying the stride between columns of a column-major matrix or rows of a row-major matrix, in basic machine units, of each of the uniforms specified by the corresponding array of uniformIndices is returned. The matrix stride of a uniform associated with the default uniform block is -1. Note that this information only makes sense for uniforms that are matrices. For uniforms that are not matrices, but are declared in a named uniform block, a matrix stride of zero is returned.

If pname is GL_UNIFORM_IS_ROW_MAJOR, then an array identifying whether each of the uniforms specified by the corresponding array of uniformIndices is a row-major matrix or not is returned. A value of one indicates a row-major matrix, and a value of zero indicates a column-major matrix, a matrix in the default uniform block, or a non-matrix.

If pname is GL_UNIFORM_ATOMIC_COUNTER_BUFFER_INDEX, then an array identifying the active atomic counter buffer index of each of the uniforms specified by the corresponding array of uniformIndices is returned. For uniforms other than atomic counters, the returned buffer index is -1. The returned indices may be passed to glGetActiveAtomicCounterBufferiv to query the properties of the associated buffer, and not necessarily the binding point specified in the uniform declaration.

## Notes

The double types, GL_DOUBLE, GL_DOUBLE_VEC2, GL_DOUBLE_VEC3, GL_DOUBLE_VEC4, GL_DOUBLE_MAT2, GL_DOUBLE_MAT3, GL_DOUBLE_MAT4, GL_DOUBLE_MAT2x3, GL_DOUBLE_MAT2x4, GL_DOUBLE_MAT3x2, GL_DOUBLE_MAT3x4, GL_DOUBLE_MAT4x2, and GL_DOUBLE_MAT4x3 are only available if the GL version is 4.1 or higher.

GL_UNIFORM_ATOMIC_COUNTER_BUFFER_INDEX is only accepted by pname if the GL version is 4.2 or higher.

## Errors

GL_INVALID_VALUE is generated if program is not a value generated by OpenGL.

GL_INVALID_OPERATION is generated if program is not a program object.

GL_INVALID_VALUE is generated if uniformCount is greater than or equal to the value of GL_ACTIVE_UNIFORMS for program.

GL_INVALID_ENUM is generated if pname is not an accepted token.

## Associated Gets

glGet with argument GL_MAX_VERTEX_UNIFORM_COMPONENTS, GL_MAX_TESS_CONTROL_UNIFORM_COMPONENTS, GL_MAX_TESS_EVALUATION_UNIFORM_COMPONENTS, GL_MAX_GEOMETRY_UNIFORM_COMPONENTS, GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, or GL_MAX_COMBINED_UNIFORM_COMPONENTS.

glGetProgram with argument GL_ACTIVE_UNIFORMS or GL_ACTIVE_UNIFORM_MAX_LENGTH.

glGetProgramInterface with GL_UNIFORM and either GL_ACTIVE_RESOURCES or GL_MAX_NAME_LENGTH

glGetProgramResourceIndex with GL_UNIFORM

## See Also

glGetActiveUniform, glGetActiveUniformName, glGetProgramResource, glGetProgramResourceName

## Copyright

Copyright © 2011 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/.