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GL_SGIX_interlace


Name


    SGIX_interlace

Name Strings


    GL_SGIX_interlace

Version


    $Date: 1995/02/22 20:58:22 $ $Revision: 1.2 $

Number


    45

Dependencies


    None.

Overview


    This extension provides a way to interlace rows of pixels when
rasterizing pixel rectangles, and loading texture images. In this
context, interlacing means skiping over rows of pixels or texels
in the destination. This is useful for dealing with video data
since a single frame of video is typically composed from two images
or fields: one image specifying the data for even rows of the frame
and the other image specifying the data for odd rows of the frame.

New Procedures and Functions


    None.

New Tokens


    Accepted by the <cap> parameter of of Enable, Disable, IsEnabled,
and by the <pname> parameter of GetBooleanv, GetIntegerv, GetFloatv,
GetDoublev:

INTERLACE_SGIX 0x8094

Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)


    None.

Additions to Chapter 3 of the 1.0 Specification (Rasterization)


    The specification of interlace operation is added the GL Specification
in section 3.6.3 "Rasterization of Pixel Rectangles", immediately
following the operations described by EXT_histogram, and immediately
prior to the subsection "Final Conversion".

The interlacing of rows of pixels is enabled or disabled with Enable or
Disable using the symbolic constant INTERLACE_SGIX. If INTERLACE_SGIX
is enabled, then all of the groups which belong to a row m are treated
as if they belonged to the row 2 * m. If the source image has a height
of h rows, this effectively expands the height of the image to 2 * h - 1
rows. After interlacing, only every other row of the image is defined.
If the interlaced pixel rectangle is rasterized to the framebuffer, then
only these rows are converted to fragments. If the interlaced pixel
rectangle is a texture image, then only these rows are written to texure
memory.

In cases where errors can result from the specification of invalid
image dimensions, it is the resulting dimensions that are tested, not
the dimensions of the source image. (A specific example is TexImage2D,
which specifies constraints for image dimensions. Even if TexImage2D
is called with a null pixel pointer, the dimensions of the resulting
texture image are those that would result from the effective expansion
of the specified image due to interlacing.)

Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations and the Frame Buffer)


    In section 4.3 "Drawing, Reading, and Copying Pixels"

INTERLACE_SGIX has no effect on the operation of ReadPixels.

Additions to Chapter 5 of the 1.0 Specification (Special Functions)


    None.

Additions to Chapter 6 of the 1.0 Specification (State and State Requests)


    None.

Additions to the GLX Specification


    None.

Errors


    None.

New State


    Get Value				Get Command			Type		Initial Value		Attribute
--------- ----------- ---- ------------- ---------
INTERLACE_SGIX IsEnabled B False pixel/enable

New Implementation Dependent State


    None.

Implementation Support


   List of OpenGL implementations supporting the GL_SGIX_interlace extension

Original File


   Original text file for the GL_SGIX_interlace extension


Page generated on Sun Nov 20 18:38:36 2005