glRasterPos4f function
Specifies the raster position for pixel operations.
Syntax
void WINAPI glRasterPos4f(
GLfloat x,
GLfloat y,
GLfloat z,
GLfloat w
);
Parameters
-
x
-
Specifies the x-coordinate for the current raster position.
-
y
-
Specifies the y-coordinate for the current raster position.
-
z
-
Specifies the z-coordinate for the current raster position.
-
w
-
The w-coordinate for the current raster position.
Return value
This function does not return a value.
Remarks
OpenGL maintains a 3-D position in window coordinates. This position, called the raster position, is maintained with subpixel accuracy. It is used to position pixel and bitmap write operations. See glBitmap, glDrawPixels, and glCopyPixels.
The current raster position consists of three window coordinates (x, y, z), a clip coordinate w value, 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. The glRasterPos4 function specifies object coordinates x, y, z, and w explicitly. The glRasterPos3 function specifies object coordinates x, y, and z explicitly, while w is implicitly set to one. The glRasterPos2 function uses the argument values for x and y while implicitly setting z and w to zero and one.
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 the 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.
Note
The raster position is modified both by glRasterPos and by glBitmap.
Note
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 the OpenGL state).
The following functions retrieve information related to glRasterPos:
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
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows 2000 Professional [desktop apps only] |
| Minimum supported server |
Windows 2000 Server [desktop apps only] |
| Header |
|
| Library |
|
| DLL |
|