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Okey; to summarise the changes... We have converted Clutter and Cogl over to using floating point internally instead of 16.16 fixed, but we have maintained the cogl-fixed API as a utility to applications in case they want to implement their own optimizations. The Clutter API has not changed (though ClutterFixed and ClutterUnit are now internally floats) but all Cogl entry points have been changed to accept floats now instead of CoglFixed. To summarise the rationale... There have been a number of issues with using fixed point though out Clutter and Cogl including: lack of precision, lack of range, excessive format conversion (GPUs tend to work nativly with IEEE floats) and maintainability. One of the main arguments for fixed point - performance - hasn't shown itself to be serious in practice so far since we seem to be more limited by GPU performance and making improvements regarding how we submit data to OpenGL[ES]/the GPU has had a more significant impact. Ref: The recent multiple rectangle queuing changes + the cogl-texture-agressive-batching branch which show significant performance gains, and that recent tests on the ipodtouch (ARM + MBX) also showed no loss of performance running with floats. So finally; please forgive the inevitable fallout, this is a far reaching change. There are still a few known issues with the fixed to float conversion but enough works for all our conformance tests to pass, and the remaining issues hopefully wont be too tricky to solve. For reference two tags will be available either side of this change: "cogl-fixed-end" and "cogl-float-start" |
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