glGetUniformfv, glGetUniformiv - Returns the value of a uniform variable

glGetActiveUniform() with arguments program and the index of an active uniform variable

       glGetProgram() with arguments program and GL_ACTIVE_UNIFORMS or GL_ACTIVE_UNIFORM_MAX_LENGTHglGetUniformLocation() with arguments program and the name of a uniform variable

       glIsProgram()

voidglGetUniformfv(GLuintprogram,GLintlocation,GLfloat*params);voidglGetUniformiv(GLuintprogram,GLintlocation,GLint*params);voidglGetUniformuiv(GLuintprogram,GLintlocation,GLuint*params);voidglGetUniformdv(GLuintprogram,GLintlocation,GLdouble*params);voidglGetnUniformfv(GLuintprogram,GLintlocation,GLsizeibufSize,GLfloat*params);voidglGetnUniformiv(GLuintprogram,GLintlocation,GLsizeibufSize,GLint*params);voidglGetnUniformuiv(GLuintprogram,GLintlocation,GLsizeibufSize,GLuint*params);voidglGetnUniformdv(GLuintprogram,GLintlocation,GLsizeibufSize,GLdouble*params);

       Copyright © 2003-2005 3Dlabs Inc. Ltd.
       Copyright © 2010-2014 Khronos Group

[FIXME: source]                                    11/18/2024                                   GLGETUNIFORM(3G)

glGetUniform and glGetnUniform return in params the value(s) of the specified uniform variable. The type
       of the uniform variable specified by location determines the number of values returned. If the uniform
       variable is defined in the shader as a boolean, int, or float, a single value will be returned. If it is
       defined as a vec2, ivec2, or bvec2, two values will be returned. If it is defined as a vec3, ivec3, or
       bvec3, three values will be returned, and so on. To query values stored in uniform variables declared as
       arrays, call glGetUniform for each element of the array. To query values stored in uniform variables
       declared as structures, call glGetUniform for each field in the structure. The values for uniform
       variables declared as a matrix will be returned in column major order.

       The locations assigned to uniform variables are not known until the program object is linked. After
       linking has occurred, the command glGetUniformLocation() can be used to obtain the location of a uniform
       variable. This location value can then be passed to glGetUniform or glGetnUniform in order to query the
       current value of the uniform variable. After a program object has been linked successfully, the index
       values for uniform variables remain fixed until the next link command occurs. The uniform variable values
       can only be queried after a link if the link was successful.

       The only difference between glGetUniform and glGetnUniform is that glGetnUniform will generate an error
       if size of the params buffer,as described by bufSize, is not large enough to hold the result data.

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_OPERATION is generated if program has not been successfully linked.

       GL_INVALID_OPERATION is generated if location does not correspond to a valid uniform variable location
       for the specified program object.

       GL_INVALID_OPERATION is generated by glGetnUniform if the buffer size required to store the requested
       data is greater than bufSize.

       glGetUniformfv, glGetUniformiv - Returns the value of a uniform variable

       If an error is generated, no change is made to the contents of params.

program
           Specifies the program object to be queried.

       location
           Specifies the location of the uniform variable to be queried.

       bufSize
           Specifies the size of the buffer params.

       params
           Returns the value of the specified uniform variable.

glCreateProgram(), glLinkProgram(), glUniform()

       ┌──────────────────┬───────────────────────────────────────────────────────────────────────┐
       │                  │                OpenGLVersion                                         │
       ├──────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
       │ Function         │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
       │ /                │     │     │     │     │     │     │     │     │     │     │     │     │
       │ Feature          │     │     │     │     │     │     │     │     │     │     │     │     │
       │ Name             │     │     │     │     │     │     │     │     │     │     │     │     │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetUniformdv   │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetUniformfv   │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetUniformiv   │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetUniformuiv  │  -  │  -  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetnUniformdv  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetnUniformfv  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetnUniformiv  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │
       ├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetnUniformuiv │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │
       └──────────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘