1991-2006
Silicon Graphics, Inc.
glRasterPos
3G

# glRasterPos

specify the raster position for pixel operations

## C Specification

                    void glRasterPos2s
                    GLshort x
                    GLshort y

                    void glRasterPos2i
                    GLint x
                    GLint y

                    void glRasterPos2f
                    GLfloat x
                    GLfloat y

                    void glRasterPos2d
                    GLdouble x
                    GLdouble y

                    void glRasterPos3s
                    GLshort x
                    GLshort y
                    GLshort z

                    void glRasterPos3i
                    GLint x
                    GLint y
                    GLint z

                    void glRasterPos3f
                    GLfloat x
                    GLfloat y
                    GLfloat z

                    void glRasterPos3d
                    GLdouble x
                    GLdouble y
                    GLdouble z

                    void glRasterPos4s
                    GLshort x
                    GLshort y
                    GLshort z
                    GLshort w

                    void glRasterPos4i
                    GLint x
                    GLint y
                    GLint z
                    GLint w

                    void glRasterPos4f
                    GLfloat x
                    GLfloat y
                    GLfloat z
                    GLfloat w

                    void glRasterPos4d
                    GLdouble x
                    GLdouble y
                    GLdouble z
                    GLdouble w

## Parameters

`x`
`y`
`z`
`w`

  Specify the x, y, z, and w object coordinates (if present) for the raster position.

## C Specification

                    void glRasterPos2sv
                    const GLshort * v

                    void glRasterPos2iv
                    const GLint * v

                    void glRasterPos2fv
                    const GLfloat * v

                    void glRasterPos2dv
                    const GLdouble * v

                    void glRasterPos3sv
                    const GLshort * v

                    void glRasterPos3iv
                    const GLint * v

                    void glRasterPos3fv
                    const GLfloat * v

                    void glRasterPos3dv
                    const GLdouble * v

                    void glRasterPos4sv
                    const GLshort * v

                    void glRasterPos4iv
                    const GLint * v

                    void glRasterPos4fv
                    const GLfloat * v

                    void glRasterPos4dv
                    const GLdouble * 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. `GL_CURRENT_RASTER_SECONDARY_COLOR` (in RGBA mode) is likewise updated.

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 by `glRasterPos`, glBitmap, and glWindowPos.

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 `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_SECONDARY_COLOR`

glGet with argument `GL_CURRENT_RASTER_INDEX`

glGet with argument `GL_CURRENT_RASTER_TEXTURE_COORDS`

## See Also

glBitmap, glCopyPixels, glDrawArrays, glDrawElements, glDrawRangeElements, glDrawPixels, glMultiTexCoord, glTexCoord, glTexGen, glVertex, glWindowPos

## Copyright

Copyright 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.