Fix math cross-platform determinism #145
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johanhelsing
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Sep 3, 2023
Jondolf
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RJ
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Sep 25, 2023
Enables the libm feature for glam to support cross-platform deterministic math when enhanced-determinism is enabled. This makes the snapshots produced by the cross-platform determinism test consistent across operating systems. The test is very simple however, so there might still be other determinism issues.
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Enables the
libmfeature for glam to support cross-platform deterministic math whenenhanced-determinismis enabled.Without the
libmfeature, our determinism test produces different snapshots across Windows, Ubuntu and MacOS. This can be seen as the CI failing in the second commit. Enablinglibmmakes the snapshots consistent across operating systems.Our test is quite straightforward however, as it just spawns a stack of cubes that falls to the ground. It doesn't test if joints, spatial queries, sleeping etc. are deterministic. We should make the test more complex to cover these different cases and verify proper determinism.
Note that even if this does fix determinism for bevy_xpbd, it's still up to the users to make sure their own code is deterministic. We should add proper documentation and tips on determinism once it's verified to work for the engine itself.