[Bf-committers] parsing Blender and math expressions?

[Benjamin Tolputt]

Campbell Barton wrote:
> While not against this (in general), keeping them fast is very
> important since they can be evaluated 100's (even 1000's) of times a
> second when running an animation on a complex rig.
> Since 2.4x, drivers compile their expressions giving ~15-25x, As well
> as caching the namespace (also gives some speedup), so I'd not accept
> a solution that is significantly slower.

This was part of the reason I thought a "nodes to Python subset" (& it's
inverse) would be beneficial. A Python subset can still be compiled by
the Python runtime and run just as fast as previously but, being a
subset with known limitations, it removes the need to try drastic
solutions such as hacking the runtime or replacing Python completely.

Obviously any subset would need to be simple yet expressive enough to
make it useful. I reckon simple conditionals, mathematical expressions
and built-in functions (for math & scene/property access) would suffice.
I don't think we need the ability to create new functions nor advanced
data types like dictionaries, lists, or objects.

The idea would need some buy in from the "decision makers" (as they
shall henceforth be known *grin*), but being able to access properties
in the scene and have basic conditionals (if not loops) would alleviate,
I think, issues about a lack of expressiveness.