| Name |
| |
| IBM_rasterpos_clip |
| |
| Name Strings |
| |
| GL_IBM_rasterpos_clip |
| |
| Version |
| |
| $Id: //depot/main/doc/registry/extensions/IBM/rasterpos_clip.spec#1 $ |
| |
| Number |
| |
| 110 |
| |
| Dependencies |
| |
| None |
| |
| Overview |
| |
| 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. |
| |
| Issues |
| |
| 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 |
| |
| New Tokens |
| |
| 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 |
| |
| GLX Protocol |
| |
| None (other than the new Enable target). |
| |
| Errors |
| |
| None |
| |
| New State |
| |
| Get Value Type Get Command Value Sec Attrib |
| ----------------------------- ---- ----------- ----- ---- ------- |
| RASTER_POSITION_UNCLIPPED_IBM B IsEnabled False 2.12 transform/ |
| enable |
| |
| New Implementation Dependent State |
| |
| None |