1Name 2 3 IBM_rasterpos_clip 4 5Name Strings 6 7 GL_IBM_rasterpos_clip 8 9Version 10 11 $Id: //depot/main/doc/registry/extensions/IBM/rasterpos_clip.spec#1 $ 12 13Number 14 15 110 16 17Dependencies 18 19 None 20 21Overview 22 23 IBM_rasterpos_clip extends the semantics of the RasterPos functions. It 24 provides an enable that allows a raster position that would normally be 25 clipped to be treated as a valid (albeit out-of-viewport) position. 26 27 This extension allows applications to specify geometry-aligned pixel 28 primitives that may be partially off-screen. These primitives are 29 tested on a pixel-by-pixel basis without being rejected completely 30 because of an invalid raster position. 31 32Issues 33 34 Currently, clipping is disabled only in X and Y. If disabling Z 35 clipping is required, the behavior needs to be specified. 36 37New Procedures and Functions 38 39 None 40 41New Tokens 42 43 Accepted by the <target> parameter of Enable and Disable and the <value> 44 parameter of IsEnabled, GetBooleanv, GetIntegerv, GetFloatv, GetDoublev: 45 46 RASTER_POSITION_UNCLIPPED_IBM 103010 47 48 The enum is subject to change if this proposal attracts interest from 49 other vendors and becomes an EXT extension. 50 51Additions to Chapter 2 of the GL Specification (OpenGL Operation) 52 53 In Section 2.12, the behavior of valid bit of the raster position with 54 respect to vertex clipping is defined. 55 56 The transformed coordinates are passed to clipping as if they 57 represented a point. If the "point" is not culled, then the 58 projection to window coordinates is computed (section 2.10) and 59 saved as the current raster position, and the valid bit is set. If 60 the "point" is culled, ... the valid bit is cleared. 61 62 The specification is modified to read: 63 64 The transformed coordinates are passed to clipping as if they 65 represented a point. If (1) the "point" is not culled, or (2) 66 RASTER_POSITION_UNCLIPPED_IBM is enabled and the "point" is not culled 67 except by the x and y components of the clip volume, then the 68 projection to window coordinates is computed (section 2.10) and saved 69 as the current raster position, and the valid bit is set. Otherwise, 70 ... the valid bit is cleared. 71 72 73Additions to Chapter 3 of the GL Specification (Rasterization) 74 75 None 76 77Additions to Chapter 4 of the GL Specification (Per-Fragment Operations 78and the Framebuffer) 79 80 None 81 82Additions to Chapter 5 of the GL Specification (Special Functions) 83 84 None 85 86Additions to Chapter 6 of the GL Specification (State and State Requests) 87 88 None 89 90Additions to the GLX Specification 91 92 None 93 94GLX Protocol 95 96 None (other than the new Enable target). 97 98Errors 99 100 None 101 102New State 103 104 Get Value Type Get Command Value Sec Attrib 105 ----------------------------- ---- ----------- ----- ---- ------- 106 RASTER_POSITION_UNCLIPPED_IBM B IsEnabled False 2.12 transform/ 107 enable 108 109New Implementation Dependent State 110 111 None 112