GLRASTERPOS() MachTen Programmer’s Manual GLRASTERPOS()

NAME
glRasterPos2d, glRasterPos2f, glRasterPos2i, glRaster-
Pos2s, glRasterPos3d, glRasterPos3f, glRasterPos3i,
glRasterPos3s, glRasterPos4d, glRasterPos4f, glRaster-
Pos4i, glRasterPos4s, glRasterPos2dv, glRasterPos2fv,
glRasterPos2iv, glRasterPos2sv, glRasterPos3dv, glRaster-
Pos3fv, glRasterPos3iv, glRasterPos3sv, glRasterPos4dv,
glRasterPos4fv, glRasterPos4iv, glRasterPos4sv - specify
the raster position for pixel operations

C SPECIFICATION
void glRasterPos2d( GLdouble x,
GLdouble y )
void glRasterPos2f( GLfloat x,
GLfloat y )
void glRasterPos2i( GLint x,
GLint y )
void glRasterPos2s( GLshort x,
GLshort y )
void glRasterPos3d( GLdouble x,
GLdouble y,
GLdouble z )
void glRasterPos3f( GLfloat x,
GLfloat y,
GLfloat z )
void glRasterPos3i( GLint x,
GLint y,
GLint z )
void glRasterPos3s( GLshort x,
GLshort y,
GLshort z )
void glRasterPos4d( GLdouble x,
GLdouble y,
GLdouble z,
GLdouble w )
void glRasterPos4f( GLfloat x,
GLfloat y,
GLfloat z,
GLfloat w )
void glRasterPos4i( GLint x,
GLint y,
GLint z,
GLint w )
void glRasterPos4s( GLshort x,
GLshort y,
GLshort z,
GLshort w )

delim $$

PARAMETERS
x, y, z, w
Specify the $x$, $y$, $z$, and $w$ object coordi-
nates (if present) for the raster position.

C SPECIFICATION
void glRasterPos2dv( const GLdouble *v )
void glRasterPos2fv( const GLfloat *v )
void glRasterPos2iv( const GLint *v )
void glRasterPos2sv( const GLshort *v )
void glRasterPos3dv( const GLdouble *v )
void glRasterPos3fv( const GLfloat *v )
void glRasterPos3iv( const GLint *v )
void glRasterPos3sv( const GLshort *v )
void glRasterPos4dv( const GLdouble *v )
void glRasterPos4fv( const GLfloat *v )
void glRasterPos4iv( const GLint *v )
void glRasterPos4sv( const GLshort *v )

PARAMETERS
v Specifies a pointer to an array of two, three, or
four elements, specifying $x$, $y$, $z$, and $w$
coordinates, respectively.

DESCRIPTION
The GL maintains a 3D position in window coordinates.
This position, called the raster position, is used to
position pixel and bitmap write operations. It is main-
tained with subpixel accuracy. See glBitmap, glDrawPix-
els, and glCopyPixels.

The current raster position consists of three window coor-
dinates ($x$, $y$, $z$), a clip coordinate value ($w$), an
eye coordinate distance, a valid bit, and associated color
data and texture coordinates. The $w$ coordinate is a
clip coordinate, because $w$ is not projected to window
coordinates. glRasterPos4 specifies object coordinates
$x$, $y$, $z$, and $w$ explicitly. glRasterPos3 specifies
object coordinate $x$, $y$, and $z$ explicitly, while $w$
is implicitly set to 1. glRasterPos2 uses the argument
values for $x$ and $y$ while implicitly setting $z$ and
$w$ to 0 and 1.

The object coordinates presented by glRasterPos are
treated just like those of a glVertex command: They are
transformed by the current modelview and projection matri-
ces and passed to the clipping stage. If the vertex is
not culled, then it is projected and scaled to window
coordinates, which become the new current raster position,
and the GL_CURRENT_RASTER_POSITION_VALID flag is set. If
the vertex is culled, then the valid bit is cleared and
the current raster position and associated color and tex-
ture coordinates are undefined.

The current raster position also includes some associated
color data and texture coordinates. If lighting is
enabled, then GL_CURRENT_RASTER_COLOR (in RGBA mode) or
GL_CURRENT_RASTER_INDEX (in color index mode) is set to
the color produced by the lighting calculation (see
glLight, glLightModel, and
glShadeModel). If lighting is disabled, current color (in
RGBA mode, state variable GL_CURRENT_COLOR) or color index
(in color index mode, state variable GL_CURRENT_INDEX) is
used to update the current raster color.

Likewise, GL_CURRENT_RASTER_TEXTURE_COORDS is updated as a
function of GL_CURRENT_TEXTURE_COORDS, based on the tex-
ture matrix and the texture generation functions (see
glTexGen). Finally, the distance from the origin of the
eye coordinate system to the vertex as transformed by only
the modelview matrix replaces GL_CURRENT_RASTER_DISTANCE.

Initially, the current raster position is (0, 0, 0, 1),
the current raster distance is 0, the valid bit is set,
the associated RGBA color is (1, 1, 1, 1), the associated
color index is 1, and the associated texture coordinates
are (0, 0, 0, 1). In RGBA mode, GL_CURRENT_RASTER_INDEX
is always 1; in color index mode, the current raster RGBA
color always maintains its initial value.

NOTES
The raster position is modified both by glRasterPos and by
glBitmap.

When the raster position coordinates are invalid, drawing
commands that are based on the raster position are ignored
(that is, they do not result in changes to GL state).

Calling glDrawElements may leave the current color or
index indeterminate. If glRasterPos is executed while the
current color or index is indeterminate, the current
raster color or current raster index remains indetermi-
nate.

To set a valid raster position outside the viewport, first
set a valid raster position, then call glBitmap with NULL
as the bitmap parameter.

ERRORS
GL_INVALID_OPERATION is generated if glRasterPos is exe-
cuted between the execution of glBegin and the correspond-
ing execution of glEnd.

ASSOCIATED GETS
glGet with argument GL_CURRENT_RASTER_POSITION
glGet with argument GL_CURRENT_RASTER_POSITION_VALID
glGet with argument GL_CURRENT_RASTER_DISTANCE
glGet with argument GL_CURRENT_RASTER_COLOR
glGet with argument GL_CURRENT_RASTER_INDEX
glGet with argument GL_CURRENT_RASTER_TEXTURE_COORDS

SEE ALSO
glBitmap, glCopyPixels, glDrawElements, glDrawPixels,
glLight, glLightModel, glShadeModel, glTexCoord, glTexGen,
glVertex

MachTen 3