1XXX - Not complete yet!!! 2 3Name 4 5 SGIX_occlusion_instrument 6 7Name Strings 8 9 GL_SGIX_occlusion_instrument 10 11Version 12 13 $Date: 1998/04/21 03:53:34 $ $Revision: 1.1 $ 14 15Number 16 17 151 18 19Dependencies 20 21 SGIX_intruments is required 22 23Overview 24 25 This extension defines an occlusion instrument that can be used by 26 applications to determine whether a set of fragments are completely 27 occluded (i.e., fail the depth test) by fragments already in the 28 frame buffer. 29 30Issues 31 32 * This extension is named like this so that developers have a better 33 idea of what the extension does instead of being obscured by a 34 device-specific name. The extension encompasses functionality that 35 is exposed by the bali_r_extension, but it does not try to address 36 the different mode of retrieving occlusion information. It's 37 possible that Bali may not be able to support this extension easily. 38 39 40New Procedures and Functions 41 42 None 43 44New Tokens 45 46 Accepted by the <cap> parameter of Enable, Disable and IsEnabled: 47 48 OCCLUSION_INSTRUMENT_SGIX 0x6060 49 50Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation) 51 52 None. 53 54Additions to Chapter 3 of the 1.1 Specification (Rasterization) 55 56 None. 57 58Additions to Chapter 4 of the 1.1 Specification (Per-Fragment Operations 59and the Frame Buffer) 60 61 Added to subsection 4.1.5 (Depth buffer test) at the end of the 62 paragraph which begins "If the depth buffer test fails...": 63 64 If OCCLUSION_INSTRUMENT_SGIX is enabled and instruments have been 65 started via a call to StartInstrumentSGIX, a flag is maintained 66 of whether fragments pass or fail the depth test. The flag's initial 67 state is TRUE and it is set to FALSE whenever a fragment generated 68 during rasterization passes the depth test. 69 70 The format of the measured occlusion instrument consists of four 71 words: the occlusion instrument enable enum (OCCLUSION_INSTRUMENT_SGIX); 72 the size of the measurement (4); the result of the measurement; and 73 the marker passed in with either StopInstrumentsSGIX or 74 ReadInstrumentsSGIX. 75 76Additions to Chapter 5 of the 1.1 Specification (Special Functions) 77 78Additions to Chapter 6 of the 1.1 Specification (State and State Requests) 79 80Additions to the GLX Specification 81 82 83Errors 84 85New State 86 87New Implementation Dependent State 88 89