glVertexPointerEXT(3G) OpenGL Reference glVertexPointerEXT(3G)
glVertexPointerEXT - define an array of vertex data
void glVertexPointerEXT( GLint size,
GLenum type,
GLsizei stride,
GLsizei count,
const GLvoid *pointer )
size Specifies the number of coordinates per vertex, must be 2,3, or
4.
type Specifies the data type of each coordinate in the array.
Symbolic constants GL_SHORT, GL_INT, GL_FLOAT, or GL_DOUBLE_EXT
are accepted.
stride Specifies the byte offset between consecutive vertices. If
stride is 0 the vertices are understood to be tightly packed in
the array.
count Specifies the number of vertices, counting from the first, that
are static.
pointer Specifies a pointer to the first coordinate of the first vertex
in the array.
glVertexPointerEXT specifies the location and data format of an array of
vertex coordinates to use when rendering using the vertex array
extension. size specifies the number of coordinates per vertex and type
the data type of the coordinates. stride gives 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.) count indicates the number of
array elements (counting from the first) that are static. Static elements
may be modified by the application, but once they are modified, the
application must explicitly respecify the array before using it for any
rendering. When a vertex array is specified, size, type, stride, count,
and pointer are saved as client-side state, and static array elements may
be cached by the implementation.
The vertex array is enabled and disabled using glEnable and glDisable
with the argument GL_VERTEX_ARRAY_EXT. If enabled, the vertex array is
used when glDrawArraysEXT or glArrayElementEXT is called.
Use glDrawArraysEXT to define a sequence of primitives (all of the same
type) from pre-specified vertex and vertex attribute arrays. Use
glArrayElementEXT to specify primitives by indexing vertices and vertex
Page 1
glVertexPointerEXT(3G) OpenGL Reference glVertexPointerEXT(3G)
attributes.
Non-static array elements are not accessed until glArrayElementEXT or
glDrawArraysEXT is executed.
By default the vertex array is disabled and it won't be accessed when
glArrayElementEXT or glDrawArraysEXT is called.
Although it is not an error to call glVertexPointerEXT between the
execution of glBegin and the corresponding execution of glEnd, the
results are undefined.
glVertexPointerEXT will typically be implemented on the client side with
no protocol.
Since the vertex array parameters are client side state, they are not
saved or restored by glPushAttrib and glPopAttrib.
glVertexPointerEXT commands are not entered into display lists.
glVertexPointerEXT is part of the EXT_vertex_array extension, not part of
the core GL command set. If GL_EXT_vertex_array is included in the string
returned by glGetString, when called with argument GL_EXTENSIONS,
extension EXT_vertex_array is supported.
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 or count is negative.
glIsEnabled with argument GL_VERTEX_ARRAY_EXT
glGet with argument GL_VERTEX_ARRAY_SIZE_EXT
glGet with argument GL_VERTEX_ARRAY_TYPE_EXT
glGet with argument GL_VERTEX_ARRAY_STRIDE_EXT
glGet with argument GL_VERTEX_ARRAY_COUNT_EXT
glGetPointervEXT with argument GL_VERTEX_ARRAY_POINTER_EXT
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,
Page 2
glVertexPointerEXT(3G) OpenGL Reference glVertexPointerEXT(3G)
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];}
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 singleprecision
floating point.
Page 3
glVertexPointerEXT(3G) OpenGL Reference glVertexPointerEXT(3G)
SEE ALSO
glArrayElementEXT, glColorPointerEXT, glDrawArraysEXT,
glEdgeFlagPointerEXT, glEnable, glGetPointervEXT, glIndexPointerEXT,
glNormalPointerEXT, glTexCoordPointerEXT
PPPPaaaaggggeeee 4444 [ Back ]
|
