Sometimes .blend files have compatibility issues between Blender versions,
because .blend files depended on the specific order of geometry elements
generated by some nodes/modifiers (#112746, #113018). While we make
guarantees about the order in some places, that is relatively rare, because it
makes future improvements much harder. The functionality in this patch
makes it easier for users to notice when they depend on things that are not
expected to be stable between Blender builds.
This is achieved by adding a new global flag which indicates whether some
algorithms should randomize their output. The functionality can be toggled
on or off by searching for `Set Geometry Randomization`. If there are no
differences (or acceptable minor ones) when the flag is on or off, one can
be reasonably sure that one does not on unspecified behavior (can't be 100%
sure though, because randomization might be missing in some places). If
there are big differences, one should consider fixing the file before it comes
to an actual breakage in the next Blender version.
Currently, the setting is only available when `Developer Extras` is turned on,
because the setting is in no menu.
With this patch, if we get bug reports with compatibility issues caused by
depending on indices, one of the following three cases should always apply:
* We actually accidentally broke something, which requires a fix commit.
* Turning on geometry randomization shows that the .blend file depends on
things it shouldn't depend on. In this case the user has to fix the file.
* We are missing geometry randomization somewhere, which requires a fix
commit.
Pull Request: https://projects.blender.org/blender/blender/pulls/113030
