fglNormalPointer(3G) OpenGL Reference fglNormalPointer(3G)NAMEfglNormalPointer - define an array of normals
FORTRAN SPECIFICATION
SUBROUTINE fglNormalPointer( INTEGER*4 type,
INTEGER*4 stride,
CHARACTER*8 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.
DESCRIPTIONfglNormalPointer 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 fglInterleavedArrays.) When a
normal array is specified, type, stride, and pointer are saved as
client-side state.
To enable and disable the normal array, call fglEnableClientState and
fglDisableClientState with the argument GL_NORMAL_ARRAY. If enabled, the
normal array is used when fglDrawArrays, fglDrawElements, or
fglArrayElement is called.
Use fglDrawArrays to construct a sequence of primitives (all of the same
type) from prespecified vertex and vertex attribute arrays. Use
fglArrayElement to specify primitives by indexing vertices and vertex
attributes and fglDrawElements to construct a sequence of primitives by
indexing vertices and vertex attributes.
NOTESfglNormalPointer is available only if the GL version is 1.1 or greater.
The normal array is initially disabled and isn't accessed when
fglArrayElement, fglDrawElements, or fglDrawArrays is called.
Execution of fglNormalPointer is not allowed between fglBegin and the
corresponding fglEnd, but an error may or may not be generated. If an
error is not generated, the operation is undefined.
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fglNormalPointer(3G) OpenGL Reference fglNormalPointer(3G)fglNormalPointer is typically implemented on the client side.
Since the normal array parameters are client-side state, they are not
saved or restored by fglPushAttrib and fglPopAttrib. Use
fglPushClientAttrib and fglPopClientAttrib 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
fglIsEnabled with argument GL_NORMAL_ARRAY
fglGet with argument GL_NORMAL_ARRAY_TYPE
fglGet with argument GL_NORMAL_ARRAY_STRIDE
fglGetPointerv 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 fglNewList and the corresponding call to fglEndList.
Instead, enable or disable before the call to fglNewList.
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
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fglNormalPointer(3G) OpenGL Reference fglNormalPointer(3G)
that all the fields described above retain their relative order and word
alignment.
An additional constraint applies when fglTexGen 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
fglArrayElement, fglColorPointer, fglDrawArrays, fglDrawElements,
fglEdgeFlagPointer, fglEnable, fglGetPointerv, fglIndexPointer,
fglInterleavedArrays, fglPopClientAttrib, fglPushClientAttrib,
fglTexCoordPointer, fglVertexPointer
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