| Name |
| |
| SGIX_interlace |
| |
| Name Strings |
| |
| GL_SGIX_interlace |
| |
| Version |
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| $Date: 1995/02/22 20:58:22 $ $Revision: 1.2 $ |
| |
| Number |
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| 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. |