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GLSL Conformance proposal

GLSL Conformance proposal. December 2004. Overview. GLSL is a complex part of OpenGL 2.0 Portability of shaders across vendors is a concern What is shader portability? 1. Well-formed source code compiles on any system ISVs can write shaders knowing they will compile

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GLSL Conformance proposal

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  1. GLSL Conformance proposal December 2004

  2. Overview • GLSL is a complex part of OpenGL 2.0 • Portability of shaders across vendors is a concern • What is shader portability? • 1. Well-formed source code compiles on any system • ISVs can write shaders knowing they will compile • 2. Compiled source code runs in a reasonably similar manner on any system. • Implementation of the language is similar across systems • 3. The GLSL object API behaves as expected on any system • Loading source code, error behavior, compile or link success and failures, attribute handling etc etc

  3. Well-formed source code compiles on any system • GLSL spec states: Compilers are required to return messages regarding lexically, grammatically or semantically incorrect shaders. • GLSL is a language in development => extensions are possible. • Extensions guided by the GLSL Extension Conventions document in the registry. • Avoids name-space collisions between vendors, between extensions and core • Extensions that alter existing behavior must be explicitly enabled in a shader • Extensions that alter semantics or syntax must be explicitly enabled in a shader This ensures ISVs get early warnings of possible non-portable code.

  4. GLSL front-end • 3Dlabs provides open-source BSD license GLSL front-end. • Front-end consists of pre-processor, lexical analyzer, parser, tree builder and semantic analyzer. • Uses code from NVIDIA for pre-processing, flex, bison and C++. • This front-end helps IHVs comply with the GLSL specification • Compilers are required to return messages regarding lexically, grammatically or semantically incorrect shaders • This front-end is used by multiple vendors. • This front-end is well tested and scrutinized. => high quality. • Bugs reported by those vendors as well as individual hobbyists. • Free support • Questions / suggestions / bug reports get prompt attention • Why do we do this? • To lessen interpretation confusion of a GLSL front-end. • To promote the use by IHVs, which will increase shader portability.

  5. GLSL parser test • 3Dlabs wrote utility to test adherence to the rule: • Compilers are required to return messages regarding lexically, grammatically or semantically incorrect shaders • BSD Open Source license • http://developer.3dlabs.com/openGL2/index.htm • Compiles 170+ shaders each aimed at testing a particular language construct. Compares compilation result to what is expected. • Some tests should compile, some should fail. • Easy to add new tests • Returns info log for each test • Reports a percentage compliance, number of passed, failed and crashed tests

  6. Results • ATI Radeon X800-PRO • Driver Catalyst 4.11 OpenGL 1.5.4707 • Passed 176 • Failed 7 • Score 96% • NVIDIA 6800 Ultra • Driver 66.93 OpenGL 1.5.2 • Passed 86 • Failed 97 • Score 47% • 3Dlabs Wildcat Realizm 100 • Driver 4.03-0199 • Passed 182 • Failed 1 • Score 99%

  7. Wrap up • Shader portability is in the best interest of ISVs and IHVs • Lexical, Syntax and Semantic compliance is the least the ARB should guideto promote shader portability. • 3Dlabs Proposes that the ARB adopts GLSL Parser Test for OpenGL 2.0 compliance.

  8. Questions?

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