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 parameter of Enable and Disable and the 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