Finer grained expressions instead of modifiers

[djeedai]

Describe the solution you'd like

As discussed on Discord having things like SetPositionSphereModifier and SetVelocitySphereModifier is restrictive, compared to having a "sphere" expression that you can plug into SetAttribute.

Describe why you want that solution. Is this related to a problem?

This reduces the maintenance burden and opens up new customizing, at the expense of a bit more setup complexity. But the Expression API is not particularly concise nor high level, and the goal is eventually for the Graph API to be the higher level entry point anyway.

Describe alternatives you've considered

• More modifiers with more customizing options; this is a maintenance burden.
• Manually building the expression; this requires a bit of math that not all users are necessarily comfortable with (and opens up to errors).