glGetActiveAttrib — Returns information about an active attribute variable for the specified program object
void glGetActiveAttrib(
|
GLuint program, |
| GLuint index, | |
| GLsizei bufSize, | |
| GLsizei *length, | |
| GLint *size, | |
| GLenum *type, | |
GLchar *name); |
program
Specifies the program object to be queried.
index
Specifies the index of the attribute variable to be queried.
bufSize
Specifies the maximum number of characters
OpenGL is allowed to write in the character buffer
indicated by name.
length
Returns the number of characters actually
written by OpenGL in the string indicated by
name (excluding the null
terminator) if a value other than
NULL is passed.
size
Returns the size of the attribute variable.
type
Returns the data type of the attribute variable.
name
Returns a null terminated string containing the name of the attribute variable.
glGetActiveAttrib returns information
about an active attribute variable in the program object
specified by program. The number of
active attributes can be obtained by calling
glGetProgram
with the value GL_ACTIVE_ATTRIBUTES. A
value of 0 for index selects the first
active attribute variable. Permissible values for
index range from zero to the number of
active attribute variables minus one.
A vertex shader may use either built-in attribute
variables, user-defined attribute variables, or both. Built-in
attribute variables have a prefix of "gl_" and
reference conventional OpenGL vertex attribtes (e.g.,
gl_Vertex,
gl_Normal, etc., see the OpenGL Shading
Language specification for a complete list.) User-defined
attribute variables have arbitrary names and obtain their values
through numbered generic vertex attributes. An attribute
variable (either built-in or user-defined) is considered active
if it is determined during the link operation that it may be
accessed during program execution. Therefore,
program should have previously been the
target of a call to
glLinkProgram,
but it is not necessary for it to have been linked
successfully.
The size of the character buffer required to store the
longest attribute variable name in
program can be obtained by calling
glGetProgram
with the value
GL_ACTIVE_ATTRIBUTE_MAX_LENGTH. This value
should be used to allocate a buffer of sufficient size to store
the returned attribute name. The size of this character buffer
is passed in bufSize, and a pointer to
this character buffer is passed in
name.
glGetActiveAttrib returns the name of
the attribute variable indicated by
index, storing it in the character buffer
specified by name. The string returned
will be null terminated. The actual number of characters written
into this buffer is returned in length,
and this count does not include the null termination character.
If the length of the returned string is not required, a value of
NULL can be passed in the
length argument.
The type argument specifies a
pointer to a variable into which the attribute variable's data type
will be written. The symbolic
constants GL_FLOAT,
GL_FLOAT_VEC2,
GL_FLOAT_VEC3,
GL_FLOAT_VEC4,
GL_FLOAT_MAT2,
GL_FLOAT_MAT3,
GL_FLOAT_MAT4,
GL_FLOAT_MAT2x3,
GL_FLOAT_MAT2x4,
GL_FLOAT_MAT3x2,
GL_FLOAT_MAT3x4,
GL_FLOAT_MAT4x2,
GL_FLOAT_MAT4x3,
GL_INT,
GL_INT_VEC2,
GL_INT_VEC3,
GL_INT_VEC4,
GL_UNSIGNED_INT,
GL_UNSIGNED_INT_VEC2,
GL_UNSIGNED_INT_VEC3,
GL_UNSIGNED_INT_VEC4,
GL_DOUBLE,
GL_DOUBLE_VEC2,
GL_DOUBLE_VEC3,
GL_DOUBLE_VEC4,
GL_DOUBLE_MAT2,
GL_DOUBLE_MAT3,
GL_DOUBLE_MAT4,
GL_DOUBLE_MAT2x3,
GL_DOUBLE_MAT2x4,
GL_DOUBLE_MAT3x2,
GL_DOUBLE_MAT3x4,
GL_DOUBLE_MAT4x2, or
GL_DOUBLE_MAT4x3
may be returned. The
size argument will return the size of the
attribute, in units of the type returned in
type.
The list of active attribute variables may include both built-in attribute variables (which begin with the prefix "gl_") as well as user-defined attribute variable names.
This function will return as much information as it can
about the specified active attribute variable. If no information
is available, length will be 0, and
name will be an empty string. This
situation could occur if this function is called after a link
operation that failed. If an error occurs, the return values
length, size,
type, and name
will be unmodified.
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_VALUE is generated if
index is greater than or equal to the
number of active attribute variables in
program.
GL_INVALID_VALUE is generated if
bufSize is less than 0.
glGet
with argument GL_MAX_VERTEX_ATTRIBS.
glGetProgram
with argument GL_ACTIVE_ATTRIBUTES or
GL_ACTIVE_ATTRIBUTE_MAX_LENGTH.
| OpenGL Version | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5 |
glGetActiveAttrib
|
✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
Copyright © 2003-2005 3Dlabs Inc. Ltd. Copyright © 2010-2014 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/.