Name
glVertexAttrib — Specifies the value of a generic vertex attribute
C Specification
void glVertexAttrib1f( | GLuint | index, |
| GLfloat | v0) ; |
void glVertexAttrib1s( | GLuint | index, |
| GLshort | v0) ; |
void glVertexAttrib1d( | GLuint | index, |
| GLdouble | v0) ; |
void glVertexAttrib2f( | GLuint | index, |
| GLfloat | v0, |
| GLfloat | v1) ; |
void glVertexAttrib2s( | GLuint | index, |
| GLshort | v0, |
| GLshort | v1) ; |
void glVertexAttrib2d( | GLuint | index, |
| GLdouble | v0, |
| GLdouble | v1) ; |
void glVertexAttrib3f( | GLuint | index, |
| GLfloat | v0, |
| GLfloat | v1, |
| GLfloat | v2) ; |
void glVertexAttrib3s( | GLuint | index, |
| GLshort | v0, |
| GLshort | v1, |
| GLshort | v2) ; |
void glVertexAttrib3d( | GLuint | index, |
| GLdouble | v0, |
| GLdouble | v1, |
| GLdouble | v2) ; |
void glVertexAttrib4f( | GLuint | index, |
| GLfloat | v0, |
| GLfloat | v1, |
| GLfloat | v2, |
| GLfloat | v3) ; |
void glVertexAttrib4s( | GLuint | index, |
| GLshort | v0, |
| GLshort | v1, |
| GLshort | v2, |
| GLshort | v3) ; |
void glVertexAttrib4d( | GLuint | index, |
| GLdouble | v0, |
| GLdouble | v1, |
| GLdouble | v2, |
| GLdouble | v3) ; |
void glVertexAttrib4Nub( | GLuint | index, |
| GLubyte | v0, |
| GLubyte | v1, |
| GLubyte | v2, |
| GLubyte | v3) ; |
Parameters
index
Specifies the index of the generic vertex
attribute to be modified.
-
v0
,
v1
,
v2
,
v3
Specifies the new values to be used for the
specified vertex attribute.
C Specification
void glVertexAttrib1fv( | GLuint | index, |
| const GLfloat * | v) ; |
void glVertexAttrib1sv( | GLuint | index, |
| const GLshort * | v) ; |
void glVertexAttrib1dv( | GLuint | index, |
| const GLdouble * | v) ; |
void glVertexAttrib2fv( | GLuint | index, |
| const GLfloat * | v) ; |
void glVertexAttrib2sv( | GLuint | index, |
| const GLshort * | v) ; |
void glVertexAttrib2dv( | GLuint | index, |
| const GLdouble * | v) ; |
void glVertexAttrib3fv( | GLuint | index, |
| const GLfloat * | v) ; |
void glVertexAttrib3sv( | GLuint | index, |
| const GLshort * | v) ; |
void glVertexAttrib3dv( | GLuint | index, |
| const GLdouble * | v) ; |
void glVertexAttrib4fv( | GLuint | index, |
| const GLfloat * | v) ; |
void glVertexAttrib4sv( | GLuint | index, |
| const GLshort * | v) ; |
void glVertexAttrib4dv( | GLuint | index, |
| const GLdouble * | v) ; |
void glVertexAttrib4iv( | GLuint | index, |
| const GLint * | v) ; |
void glVertexAttrib4bv( | GLuint | index, |
| const GLbyte * | v) ; |
void glVertexAttrib4ubv( | GLuint | index, |
| const GLubyte * | v) ; |
void glVertexAttrib4usv( | GLuint | index, |
| const GLushort * | v) ; |
void glVertexAttrib4uiv( | GLuint | index, |
| const GLuint * | v) ; |
void glVertexAttrib4Nbv( | GLuint | index, |
| const GLbyte * | v) ; |
void glVertexAttrib4Nsv( | GLuint | index, |
| const GLshort * | v) ; |
void glVertexAttrib4Niv( | GLuint | index, |
| const GLint * | v) ; |
void glVertexAttrib4Nubv( | GLuint | index, |
| const GLubyte * | v) ; |
void glVertexAttrib4Nusv( | GLuint | index, |
| const GLushort * | v) ; |
void glVertexAttrib4Nuiv( | GLuint | index, |
| const GLuint * | v) ; |
Parameters
index
Specifies the index of the generic vertex
attribute to be modified.
v
Specifies a pointer to an array of values to
be used for the generic vertex attribute.
Description
OpenGL defines a number of standard vertex attributes that
applications can modify with standard API entry points (color,
normal, texture coordinates, etc.). The
glVertexAttrib
family of entry points
allows an application to pass generic vertex attributes in
numbered locations.
Generic attributes are defined as four-component values
that are organized into an array. The first entry of this array
is numbered 0, and the size of the array is specified by the
implementation-dependent constant
GL_MAX_VERTEX_ATTRIBS
. Individual elements
of this array can be modified with a
glVertexAttrib
call that specifies the
index of the element to be modified and a value for that
element.
These commands can be used to specify one, two, three, or
all four components of the generic vertex attribute specified by
index
. A 1
in the
name of the command indicates that only one value is passed, and
it will be used to modify the first component of the generic
vertex attribute. The second and third components will be set to
0, and the fourth component will be set to 1. Similarly, a
2
in the name of the command indicates that
values are provided for the first two components, the third
component will be set to 0, and the fourth component will be set
to 1. A 3
in the name of the command
indicates that values are provided for the first three
components and the fourth component will be set to 1, whereas a
4
in the name indicates that values are
provided for all four components.
The letters s
,
f
, i
,
d
, ub
,
us
, and ui
indicate
whether the arguments are of type short, float, int, double,
unsigned byte, unsigned short, or unsigned int. When
v
is appended to the name, the commands can
take a pointer to an array of such values. The commands
containing N
indicate that the arguments
will be passed as fixed-point values that are scaled to a
normalized range according to the component conversion rules
defined by the OpenGL specification. Signed values are
understood to represent fixed-point values in the range [-1,1],
and unsigned values are understood to represent fixed-point
values in the range [0,1].
OpenGL Shading Language attribute variables are allowed to
be of type mat2, mat3, or mat4. Attributes of these types may be
loaded using the glVertexAttrib
entry
points. Matrices must be loaded into successive generic
attribute slots in column major order, with one column of the
matrix in each generic attribute slot.
A user-defined attribute variable declared in a vertex
shader can be bound to a generic attribute index by calling
glBindAttribLocation.
This allows an application to use more descriptive variable
names in a vertex shader. A subsequent change to the specified
generic vertex attribute will be immediately reflected as a
change to the corresponding attribute variable in the vertex
shader.
The binding between a generic vertex attribute index and a
user-defined attribute variable in a vertex shader is part of
the state of a program object, but the current value of the
generic vertex attribute is not. The value of each generic
vertex attribute is part of current state, just like standard
vertex attributes, and it is maintained even if a different
program object is used.
An application may freely modify generic vertex attributes
that are not bound to a named vertex shader attribute variable.
These values are simply maintained as part of current state and
will not be accessed by the vertex shader. If a generic vertex
attribute bound to an attribute variable in a vertex shader is
not updated while the vertex shader is executing, the vertex
shader will repeatedly use the current value for the generic
vertex attribute.
The generic vertex attribute with index 0 is the same as
the vertex position attribute previously defined by OpenGL. A
glVertex2,
glVertex3,
or
glVertex4
command is completely equivalent to the corresponding
glVertexAttrib
command with an index
argument of 0. A vertex shader can access generic vertex
attribute 0 by using the built-in attribute variable
gl_Vertex
. There are no current values
for generic vertex attribute 0. This is the only generic vertex
attribute with this property; calls to set other standard vertex
attributes can be freely mixed with calls to set any of the
other generic vertex attributes.
Notes
glVertexAttrib
is available only if
the GL version is 2.0 or greater.
Generic vertex attributes can be updated at any time. In
particular, glVertexAttrib
can be called
between a call to
glBegin
and the corresponding call to
glEnd.
It is possible for an application to bind more than one
attribute name to the same generic vertex attribute index. This
is referred to as aliasing, and it is allowed only if just one
of the aliased attribute variables is active in the vertex
shader, or if no path through the vertex shader consumes more
than one of the attributes aliased to the same location. OpenGL
implementations are not required to do error checking to detect
aliasing, they are allowed to assume that aliasing will not
occur, and they are allowed to employ optimizations that work
only in the absence of aliasing.
There is no provision for binding standard vertex
attributes; therefore, it is not possible to alias generic
attributes with standard attributes.
Errors
GL_INVALID_VALUE
is generated if
index
is greater than or equal to
GL_MAX_VERTEX_ATTRIBS
.
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/.