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GLBINDATTRIBLOCATION(3G)                         OpenGL 3.3                         GLBINDATTRIBLOCATION(3G)



NAME
       glBindAttribLocation - Associates a generic vertex attribute index with a named attribute variable

C SPECIFICATION
       void glBindAttribLocation(GLuint program, GLuint index, const GLchar *name);

PARAMETERS
       program
           Specifies the handle of the program object in which the association is to be made.

       index
           Specifies the index of the generic vertex attribute to be bound.

       name
           Specifies a null terminated string containing the name of the vertex shader attribute variable to
           which index is to be bound.

DESCRIPTION
       glBindAttribLocation is used to associate a user-defined attribute variable in the program object
       specified by program with a generic vertex attribute index. The name of the user-defined attribute
       variable is passed as a null terminated string in name. The generic vertex attribute index to be
       bound to this variable is specified by index. When program is made part of current state, values
       provided via the generic vertex attribute index will modify the value of the user-defined attribute
       variable specified by name.

       If name refers to a matrix attribute variable, index refers to the first column of the matrix. Other
       matrix columns are then automatically bound to locations index+1 for a matrix of type mat2; index+1
       and index+2 for a matrix of type mat3; and index+1, index+2, and index+3 for a matrix of type mat4.

       This command makes it possible for vertex shaders to use descriptive names for attribute variables
       rather than generic variables that are numbered from 0 to GL_MAX_VERTEX_ATTRIBS -1. The values sent
       to each generic attribute index are part of current state. If a different program object is made
       current by calling glUseProgram(), the generic vertex attributes are tracked in such a way that the
       same values will be observed by attributes in the new program object that are also bound to index.

       Attribute variable name-to-generic attribute index bindings for a program object can be explicitly
       assigned at any time by calling glBindAttribLocation. Attribute bindings do not go into effect until
       glLinkProgram() is called. After a program object has been linked successfully, the index values for
       generic attributes remain fixed (and their values can be queried) until the next link command occurs.

       Any attribute binding that occurs after the program object has been linked will not take effect until
       the next time the program object is linked.

NOTES
       glBindAttribLocation can be called before any vertex shader objects are bound to the specified
       program object. It is also permissible to bind a generic attribute index to an attribute variable
       name that is never used in a vertex shader.

       If name was bound previously, that information is lost. Thus you cannot bind one user-defined
       attribute variable to multiple indices, but you can bind multiple user-defined attribute variables to
       the same index.

       Applications are allowed to bind more than one user-defined attribute variable to the same generic
       vertex attribute index. This is called aliasing, and it is allowed only if just one of the aliased
       attributes is active in the executable program, or if no path through the shader consumes more than
       one attribute of a set of attributes aliased to the same location. The compiler and linker are
       allowed to assume that no aliasing is done and are free to employ optimizations that work only in the
       absence of aliasing. OpenGL implementations are not required to do error checking to detect aliasing.

       Active attributes that are not explicitly bound will be bound by the linker when glLinkProgram() is
       called. The locations assigned can be queried by calling glGetAttribLocation().

       OpenGL copies the name string when glBindAttribLocation is called, so an application may free its
       copy of the name string immediately after the function returns.

       Generic attribute locations may be specified in the shader source text using a location layout
       qualifier. In this case, the location of the attribute specified in the shader's source takes
       precedence and may be queried by calling glGetAttribLocation().

ERRORS
       GL_INVALID_VALUE is generated if index is greater than or equal to GL_MAX_VERTEX_ATTRIBS.

       GL_INVALID_OPERATION is generated if name starts with the reserved prefix "gl_".

       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.

ASSOCIATED GETS
       glGet() with argument GL_MAX_VERTEX_ATTRIBS

       glGetActiveAttrib() with argument program

       glGetAttribLocation() with arguments program and name

       glIsProgram()

SEE ALSO
       glDisableVertexAttribArray(), glEnableVertexAttribArray(), glUseProgram(), glVertexAttrib(),
       glVertexAttribPointer()


COPYRIGHT
       Copyright (C) 2003-2005 3Dlabs Inc. Ltd. 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/.



OpenGL 3.3                                       03/08/2011                         GLBINDATTRIBLOCATION(3G)