glNormalPointerEXT(3G) OpenGL Reference glNormalPointerEXT(3G)
NAME
glNormalPointerEXT - define a array of normals
C SPECIFICATION
void glNormalPointerEXT( GLenum type,
GLsizei stride,
GLsizei count,
const GLvoid *pointer )
PARAMETERS
type Specifies the the data type of each coordinate in the array.
Symbolic constants GLBYTE, GLSHORT, GLINT, GLFLOAT, or
GLDOUBLEEXT are accepted.
stride Specifies the byte offset between consecutive normals.
count Specifies the number of normals, counting from the first, that
are static.
pointer Specifies a pointer to the first coordinate of the first normal
in the array.
DESCRIPTION
glNormalPointerEXT specifies the location and data format of an array of
normals to use when rendering using the vertex array extension. type
specifies the data type of the normal coordinates and stride gives the
byte stride from one normal to the next allowing vertexes 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 normal array is specified, type,
stride, count and pointer are saved as client-side state, and static
array elements may be cached by the implementation.
The normal array is enabled and disabled using glEnable and glDisable
with the argument GLNORMALARRAYEXT. If enabled, the normal 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 vertexes and vertex
attributes.
NOTES
Non-static array elements are not accessed until glArrayElementEXT or
glDrawArraysEXT is executed.
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glNormalPointerEXT(3G) OpenGL Reference glNormalPointerEXT(3G)
By default the normal array is disabled and it won't be accessed when
glArrayElementEXT or glDrawArraysEXT is called.
Although it is not an error to call glNormalPointerEXT between the
execution of glBegin and the corresponding execution of glEnd, the
results are undefined.
glNormalPointerEXT will typically be implemented on the client side with
no protocol.
Since the normal array parameters are client side state, they are not
saved or restored by glPushAttrib and glPopAttrib.
glNormalPointerEXT commands are not entered into display lists.
glNormalPointerEXT is part of the EXTvertexarray extension, not part of
the core GL command set. If GLEXTvertexarray is included in the string
returned by glGetString, when called with argument GLEXTENSIONS,
extension EXTvertexarray is supported.
ERRORS
GLINVALIDENUM is generated if type is not an accepted value.
GLINVALIDVALUE is generated if stride or count is negative.
ASSOCIATED GETS
glIsEnabled with argument GLNORMALARRAYEXT
glGet with argument GLNORMALARRAYTYPEEXT
glGet with argument GLNORMALARRAYSTRIDEEXT
glGet with argument GLNORMALARRAYCOUNTEXT
glGetPointervEXT with argument GLNORMALARRAYPOINTEREXT
MACHINE DEPENDENCIES
On RealityEngine, RealityEngine2, and VTX systems, do not enable or
disable GLVERTEXARRAY, GLVERTEXARRAYEXT, GLNORMALARRAY,
GLNORMALARRAYEXT, GLCOLORARRAY, GLCOLORARRAYEXT,
GLINDEXARRAY,GLINDEXARRAYEXT, GLTEXTURECOORDARRAY,
GLTEXTURECOORDARRAYEXT, GLEDGEFLAGARRAY or GLEDGEFLAGARRAYEXT
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
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glNormalPointerEXT(3G) OpenGL Reference glNormalPointerEXT(3G)
is to use properly-aligned byte and short data types whenever possible.
Accordingly, the EXTvertexarray 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
GLOBJECTLINEAR 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
glArrayElementEXT, glColorPointerEXT, glDrawArraysEXT,
glEdgeFlagPointerEXT, glEnable, glGetPointervEXT, glIndexPointerEXT,
glTexCoordPointerEXT, glVertexPointerEXT
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