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:
┌──────────────────────────────────────────────┬──────────────────────┐
│ ReturnedSymbolicContant │ ShaderUniformType │
├──────────────────────────────────────────────┼──────────────────────┤
│ 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 │ unsignedint │
├──────────────────────────────────────────────┼──────────────────────┤
│ 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.
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