glGetUniformLocation — Returns the location of a uniform variable
GLint glGetUniformLocation( | GLuint | program, |
| const GLchar * | name); |
programSpecifies the program object to be queried.
namePoints to a null terminated string containing the name of the uniform variable whose location is to be queried.
glGetUniformLocation returns an
integer that represents the location of a specific uniform
variable within a program object. name
must be a null terminated string that contains no white space.
name must be an active uniform variable
name in program that is not a structure,
an array of structures, or a subcomponent of a vector or a
matrix. This function returns -1 if name
does not correspond to an active uniform variable in
program or if name
starts with the reserved prefix "gl_".
Uniform variables that are structures or arrays of
structures may be queried by calling
glGetUniformLocation for each field within
the structure. The array element operator "[]" and the
structure field operator "." may be used in
name in order to select elements within
an array or fields within a structure. The result of using these
operators is not allowed to be another structure, an array of
structures, or a subcomponent of a vector or a matrix. Except if
the last part of name indicates a uniform
variable array, the location of the first element of an array
can be retrieved by using the name of the array, or by using the
name appended by "[0]".
The actual locations assigned to uniform variables are not
known until the program object is linked successfully. 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
glUniform
to set the value of the uniform variable or to
glGetUniform
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. Uniform variable locations and values can only
be queried after a link if the link was successful.
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
glGetUniformLocation is executed between
the execution of
glBegin
and the corresponding execution of
glEnd.
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_LENGTH
glGetUniform
with arguments program and the name of a
uniform variable
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