glVertexPointer(3G) OpenGL Reference glVertexPointer(3G)NAME
glVertexPointer - define an array of vertex data
C SPECIFICATION
void glVertexPointer( GLint size,
GLenum type,
GLsizei stride,
const GLvoid *pointer )
PARAMETERS
size Specifies the number of coordinates per vertex; must be 2, 3, or
4. The initial value is 4.
type Specifies the data type of each coordinate in the array.
Symbolic constants GL_SHORT, GL_INT, GL_FLOAT, and GL_DOUBLE are
accepted. The initial value is GL_FLOAT.
stride Specifies the byte offset between consecutive vertices. If
stride is 0, the vertices are understood to be tightly packed in
the array. The initial value is 0.
pointer Specifies a pointer to the first coordinate of the first vertex
in the array. The initial value is 0.
DESCRIPTION
glVertexPointer specifies the location and data format of an array of
vertex coordinates to use when rendering. size specifies the number of
coordinates per vertex and type the data type of the coordinates. stride
specifies the byte stride from one vertex to the next allowing vertices
and attributes to be packed into a single array or stored in separate
arrays. (Single-array storage may be more efficient on some
implementations; see glInterleavedArrays.) When a vertex array is
specified, size, type, stride, and pointer are saved as client-side
state.
To enable and disable the vertex array, call glEnableClientState and
glDisableClientState with the argument GL_VERTEX_ARRAY. If enabled, the
vertex array is used when glDrawArrays, glDrawElements, or glArrayElement
is called.
Use glDrawArrays to construct a sequence of primitives (all of the same
type) from prespecified vertex and vertex attribute arrays. Use
glArrayElement to specify primitives by indexing vertices and vertex
attributes and glDrawElements to construct a sequence of primitives by
indexing vertices and vertex attributes.
NOTES
glVertexPointer is available only if the GL version is 1.1 or greater.
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glVertexPointer(3G) OpenGL Reference glVertexPointer(3G)
The vertex array is initially disabled and isn't accessed when
glArrayElement, glDrawElements or glDrawArrays is called.
Execution of glVertexPointer is not allowed between the execution of
glBegin and the corresponding execution of glEnd, but an error may or may
not be generated. If no error is generated, the operation is undefined.
glVertexPointer is typically implemented on the client side.
Vertex array parameters are client-side state and are therefore not saved
or restored by glPushAttrib and glPopAttrib. Use glPushClientAttrib and
glPopClientAttrib instead.
ERRORS
GL_INVALID_VALUE is generated if size is not 2, 3, or 4.
GL_INVALID_ENUM is generated if type is is not an accepted value.
GL_INVALID_VALUE is generated if stride is negative.
ASSOCIATED GETS
glIsEnabled with argument GL_VERTEX_ARRAY
glGet with argument GL_VERTEX_ARRAY_SIZE
glGet with argument GL_VERTEX_ARRAY_TYPE
glGet with argument GL_VERTEX_ARRAY_STRIDE
glGetPointerv with argument GL_VERTEX_ARRAY_POINTER
MACHINE DEPENDENCIES
On RealityEngine, RealityEngine2, and VTX systems, do not enable or
disable GL_VERTEX_ARRAY, GL_VERTEX_ARRAY_EXT, GL_NORMAL_ARRAY,
GL_NORMAL_ARRAY_EXT, GL_COLOR_ARRAY, GL_COLOR_ARRAY_EXT,
GL_INDEX_ARRAY,GL_INDEX_ARRAY_EXT, GL_TEXTURE_COORD_ARRAY,
GL_TEXTURE_COORD_ARRAY_EXT, GL_EDGE_FLAG_ARRAY or GL_EDGE_FLAG_ARRAY_EXT
between a call to glNewList and the corresponding call to glEndList.
Instead, enable or disable before the call to glNewList.
On InfiniteReality systems it is particularly important to minimize the
amount of data transferred from the application to the graphics pipe,
since the host-to-pipe bandwidth limit can cause a performance
bottleneck. One way to reduce the amount of data transferred per vertex
is to use properly-aligned byte and short data types whenever possible.
Accordingly, the EXT_vertex_array extension on InfiniteReality systems
has been optimized for vertex information packed into the following data
structures. (Note: v represents vertex coordinates, c represents color
components, n represents normal coordinates, and t represents texture
coordinates. Normals must have unit length.)
struct {GLfloat v[3];}
struct {GLubyte c[4]; GLfloat v[3];}
struct {GLshort n[3]; GLfloat v[3];}
struct {GLubyte c[4]; GLshort n[3]; GLfloat v[3];}
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glVertexPointer(3G) OpenGL Reference glVertexPointer(3G)
struct {GLshort t[2]; GLfloat v[3];}
struct {GLshort t[2]; GLubyte c[4]; GLfloat v[3];}
struct {GLshort t[2]; GLshort n[3]; GLfloat v[3];}
struct {GLshort t[2]; GLubyte c[4]; GLshort n[3]; GLfloat v[3];}
struct {GLfloat t[2]; GLfloat v[3];}
struct {GLfloat t[2]; GLubyte c[4]; GLfloat v[3];}
struct {GLfloat t[2]; GLshort n[3]; GLfloat v[3];}
struct {GLfloat t[2]; GLubyte c[4]; GLshort n[3]; GLfloat v[3];}
Application-specific fields may be added to these structures, provided
that all the fields described above retain their relative order and word
alignment.
An additional constraint applies when glTexGen is being used. The
implementation normally generates all four texture coordinates in
parallel, and must take special action to generate just a subset of the
four coordinates. Therefore performance is best when none of the texture
coordinates are being generated, or when all of them are being generated.
For example, when using 2D texturing (generating s and t coordinates) it
will be faster to enable texture coordinate generation for the r and q
coordinates as well as s and t. Choose a texture generation mode of
GL_OBJECT_LINEAR and use the plane equations (0,0,0,0) and (0,0,0,1) for
r and q, respectively.
Using these structures on InfiniteReality systems can improve performance
considerably, compared to structures in which all values are single-
precision floating point.
SEE ALSO
glArrayElement, glColorPointer, glDrawArrays, glDrawElements,
glDrawRangeElements, glEdgeFlagPointer, glEnable, glGetPointerv,
glIndexPointer, glInterleavedArrays, glNormalPointer, glPopClientAttrib,
glPushClientAttrib, glTexCoordPointer
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