VSE: make Gamma Cross effect 4x faster #115801

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Aras Pranckevicius merged 1 commits from aras_p/blender:vse-gammacross-opt into main 2023-12-06 19:37:11 +01:00

Gamma Cross code seems to be coming from year 2005 or earlier, with complex table based machinery to approximate "raise to power" calculations. Which, for Gamma Cross, have always been hardcoded to 2.0 "since forever". So simplify all that, i.e. replace all the table lookup/interpolation things with just x*x and sqrt(x).

Applying Gamma Cross on 4K UHD resolution, Windows Ryzen 5950X machine: 36.2ms -> 8.1ms

Gamma Cross code seems to be coming from year 2005 or earlier, with complex table based machinery to approximate "raise to power" calculations. Which, for Gamma Cross, have always been hardcoded to 2.0 "since forever". So simplify all that, i.e. replace all the table lookup/interpolation things with just `x*x` and `sqrt(x)`. Applying Gamma Cross on 4K UHD resolution, Windows Ryzen 5950X machine: 36.2ms -> 8.1ms
Aras Pranckevicius added 1 commit 2023-12-05 14:42:48 +01:00
buildbot/vexp-code-patch-coordinator Build done. Details
8a5bbb7967
VSE: speedup Gamma Cross effect
Gamma Cross code seems to be coming from year 2005 or earlier, with
complex table based machinery to approximate "raise to power"
calculations. Which, for Gamma Cross, have always been hardcoded to
2.0 "since forever". Which is either just "x*x" or "sqrt(x)".

So just do that. Applying Gamma Cross on 4K UHD resolution, Windows
Ryzen 5950X machine: 36.2ms -> 8.1ms
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@blender-bot build

@blender-bot build
Aras Pranckevicius requested review from Richard Antalik 2023-12-05 16:29:42 +01:00
Aras Pranckevicius added this to the Video Sequencer project 2023-12-05 16:30:15 +01:00
Aras Pranckevicius changed title from VSE: speedup Gamma Cross effect to VSE: make Gamma Cross effect 4x faster 2023-12-06 08:52:19 +01:00
Richard Antalik approved these changes 2023-12-06 18:56:57 +01:00
Richard Antalik left a comment
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Nice simplification! I have hard time imagining the original code was faster even in 2005.

Nice simplification! I have hard time imagining the original code was faster even in 2005.
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I have hard time imagining the original code was faster even in 2005

Around 2005 it was seemingly re-added from some other place. If it was written in 1999 or so, back when doing a square root was "unimaginable cost", then I could imagine an interpolating table lookup being faster :)

> I have hard time imagining the original code was faster even in 2005 Around 2005 it was seemingly re-added from some other place. If it was written in 1999 or so, back when doing a square root was "unimaginable cost", then I could imagine an interpolating table lookup being faster :)
Aras Pranckevicius merged commit 9cbc96194e into main 2023-12-06 19:37:11 +01:00
Aras Pranckevicius deleted branch vse-gammacross-opt 2023-12-06 19:37:13 +01:00
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