glNormalPointer(3G)

NAME
     glNormalPointer - define an array of normals


C SPECIFICATION
     void glNormalPointer( GLenum type,
                           GLsizei stride,
                           const GLvoid *pointer )


PARAMETERS
     type     Specifies the data type of each coordinate in the array.
              Symbolic constants GL_BYTE, GL_SHORT, GL_INT, GL_FLOAT, and
              GL_DOUBLE are accepted. The initial value is GL_FLOAT.

     stride   Specifies the byte offset between consecutive normals. If stride
              is 0- the initial value-the normals 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 normal
              in the array. The initial value is 0.

DESCRIPTION
     glNormalPointer specifies the location and data format of an array of
     normals to use when rendering.  type specifies the data type of the
     normal coordinates and stride gives the byte stride from one normal 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
     normal array is specified, type, stride, and pointer are saved as
     client-side state.

     To enable and disable the normal array, call glEnableClientState and
     glDisableClientState with the argument GL_NORMAL_ARRAY. If enabled, the
     normal 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
     glNormalPointer is available only if the GL version is 1.1 or greater.

     The normal array is initially disabled and isn't accessed when
     glArrayElement, glDrawElements, or glDrawArrays is called.

     Execution of glNormalPointer is not allowed between glBegin and the
     corresponding glEnd, but an error may or may not be generated. If an
     error is not generated, the operation is undefined.
     glNormalPointer is typically implemented on the client side.

     Since the normal array parameters are client-side state, they are not
     saved or restored by glPushAttrib and glPopAttrib.  Use
     glPushClientAttrib and glPopClientAttrib instead.

ERRORS
     GL_INVALID_ENUM is generated if type is not an accepted value.

     GL_INVALID_VALUE is generated if stride is negative.

ASSOCIATED GETS
     glIsEnabled with argument GL_NORMAL_ARRAY
     glGet with argument GL_NORMAL_ARRAY_TYPE
     glGet with argument GL_NORMAL_ARRAY_STRIDE
     glGetPointerv with argument GL_NORMAL_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];}
          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,
     glEdgeFlagPointer, glEnable, glGetPointerv, glIndexPointer,
     glInterleavedArrays, glPopClientAttrib, glPushClientAttrib,
     glTexCoordPointer, glVertexPointer