GLAPI/glGetUniformLocation: Difference between revisions
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== Function Definition == | == Function Definition == | ||
GLint '''glGetUniformLocation'''(GLuint | GLint '''glGetUniformLocation'''(GLuint {{param|program}}, const GLchar *{{param|name}}); | ||
; program | ; program | ||
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== Description == | == Description == | ||
'''glGetUniformLocation''' returns an integer that represents the location of a specific uniform variable within a program object. | '''glGetUniformLocation''' returns an integer that represents the location of a specific uniform variable within a program object. {{param|name}} must be a null terminated string that contains no white space. {{param|name}} must be an active uniform variable name in {{param|program}} that is not a structure, an array of structures, or a subcomponent of a vector or a matrix. This function returns -1 if {{param|name}} does not correspond to an active uniform variable in {{param|program}}, if {{param|name}} starts with the reserved prefix "gl_", or if {{param|name}} is associated with an atomic counter or a named uniform block. | ||
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 | 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 {{param|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 {{param|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 | 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 {{apifunc|glUniform}} to set the value of the uniform variable or to {{apifunc|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. | ||
== Errors == | == Errors == | ||
{{ | {{enum|GL_INVALID_VALUE}} is generated if {{param|program}} is not a value generated by OpenGL. | ||
{{ | {{enum|GL_INVALID_OPERATION}} is generated if {{param|program}} is not a program object. | ||
{{ | {{enum|GL_INVALID_OPERATION}} is generated if {{param|program}} has not been successfully linked. | ||
== Associated Gets == | == Associated Gets == | ||
{{apifunc|glGetActiveUniform}} with arguments {{param|program}} and the index of an active uniform variable | |||
{{apifunc|glGetProgram}} with arguments {{param|program}} and {{enum|GL_ACTIVE_UNIFORMS}} or {{enum|GL_ACTIVE_UNIFORM_MAX_LENGTH}} | |||
{{apifunc|glGetUniform}} with arguments {{param|program}} and the name of a uniform variable | |||
{{apifunc|glIsProgram}} | |||
== See Also == | == See Also == | ||
{{apifunc|glUniform}}, {{apifunc|glGetProgramResourceLocation}} | |||
== Copyright == | == Copyright == | ||
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Copyright © 2003-2005 3Dlabs Inc. Ltd. © 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/ http://opencontent.org/openpub/]. | Copyright © 2003-2005 3Dlabs Inc. Ltd. © 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/ http://opencontent.org/openpub/]. | ||
[[Category:API Reference | [[Category:Core API Ref Shader Program Query|GetUniformLocation]] | ||
[[Category:Core API Reference|GetUniformLocation]] | |||
[[Category:Program Object API State Functions|GetUniformLocation]] | |||
Latest revision as of 10:02, 15 August 2013
| Core in version | 4.6 | |
|---|---|---|
| Core since version | 2.0 | |
glGetUniformLocation: Returns the location of a uniform variable
Function Definition
GLint glGetUniformLocation(GLuint program, const GLchar *name);
- program
- Specifies the program object to be queried.
- name
- Points to a null terminated string containing the name of the uniform variable whose location is to be queried.
Description
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, if name starts with the reserved prefix "gl_", or if name is associated with an atomic counter or a named uniform block.
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.
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_OPERATION is generated if program has not been successfully linked.
Associated Gets
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
See Also
glUniform, glGetProgramResourceLocation
Copyright
Copyright © 2003-2005 3Dlabs Inc. Ltd. © 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/.