GLRASTERPOS(3G)GLRASTERPOS(3G)NAME
glRasterPos2d, glRasterPos2f, glRasterPos2i, glRasterPos2s,
glRasterPos3d, glRasterPos3f, glRasterPos3i, glRasterPos3s,
glRasterPos4d, glRasterPos4f, glRasterPos4i, glRasterPos4s,
glRasterPos2dv, glRasterPos2fv, glRasterPos2iv, glRasterPos2sv,
glRasterPos3dv, glRasterPos3fv, 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 coordinates (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 maintained with subpixel accuracy. See glBitmap,
glDrawPixels, and glCopyPixels.
The current raster position consists of three window coordinates ($x$,
$y$, $z$), 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 matrices 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 texture 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 texture 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, or glDrawRangeElements 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 indeterminate.
To set a valid raster position outside the viewport, first set a valid
raster position, then call glBitmap with NULL as the bitmap parameter.
When the GL_ARB_imaging extension is supported, there are distinct
raster texture coordinates for each texture unit. Each texture unit's
current raster texture coordinates are updated by glRasterPos.
ERRORS
GL_INVALID_OPERATION is generated if glRasterPos is executed between
the execution of glBegin and the corresponding 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 ALSOglBitmap(3G), glCopyPixels(3G), glDrawArrays(3G), glDrawElements(3G),
glDrawRangeElements(3G), glDrawPixels(3G), glTexCoord(3G),
glTexGen(3G), glVertex(3G)
March 1, 2011
