IBM_rasterpos_clip
GL_IBM_rasterpos_clip
$Id: //depot/main/doc/registry/extensions/IBM/rasterpos_clip.spec#1 $
110
None
IBM_rasterpos_clip extends the semantics of the RasterPos functions. It
provides an enable that allows a raster position that would normally be
clipped to be treated as a valid (albeit out-of-viewport) position.
This extension allows applications to specify geometry-aligned pixel
primitives that may be partially off-screen. These primitives are
tested on a pixel-by-pixel basis without being rejected completely
because of an invalid raster position.
Currently, clipping is disabled only in X and Y. If disabling Z
clipping is required, the behavior needs to be specified.
   New Procedures and Functions |
None
Accepted by the <target> parameter of Enable and Disable and the <value>
parameter of IsEnabled, GetBooleanv, GetIntegerv, GetFloatv, GetDoublev:
RASTER_POSITION_UNCLIPPED_IBM 103010
The enum is subject to change if this proposal attracts interest from
other vendors and becomes an EXT extension.
| Additions to Chapter 2 of the GL Specification (OpenGL Operation) |
In Section 2.12, the behavior of valid bit of the raster position with
respect to vertex clipping is defined.
The transformed coordinates are passed to clipping as if they
represented a point. If the "point" is not culled, then the
projection to window coordinates is computed (section 2.10) and
saved as the current raster position, and the valid bit is set. If
the "point" is culled, ... the valid bit is cleared.
The specification is modified to read:
The transformed coordinates are passed to clipping as if they
represented a point. If (1) the "point" is not culled, or (2)
RASTER_POSITION_UNCLIPPED_IBM is enabled and the "point" is not culled
except by the x and y components of the clip volume, then the
projection to window coordinates is computed (section 2.10) and saved
as the current raster position, and the valid bit is set. Otherwise,
... the valid bit is cleared.
| Additions to Chapter 3 of the GL Specification (Rasterization) |
None
| Additions to Chapter 4 of the GL Specification (Per-Fragment Operations and the Framebuffer) |
None
| Additions to Chapter 5 of the GL Specification (Special Functions) |
None
| Additions to Chapter 6 of the GL Specification (State and State Requests) |
None
| Additions to the GLX Specification |
None
None (other than the new Enable target).
None
Get Value Type Get Command Value Sec Attrib
----------------------------- ---- ----------- ----- ---- -------
RASTER_POSITION_UNCLIPPED_IBM B IsEnabled False 2.12 transform/
enable
| New Implementation Dependent State |
None
None
 |  | Last update: November 14, 2006.
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