glBindAttribLocation man page on Oracle
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GLBINDATTRIBLOCATION(3G) OpenGL Manual 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 © 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/.
AUTHORS
opengl.org
opengl.org 04/29/2014 GLBINDATTRIBLOCATION(3G)
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