Node affectors

[ohlidalp]

Affectors are actuators which apply force to nodes. Applying forces from script or GUI is not trivial because physics runs at 2000FPS while Script/GUI are updated once per frame (roughly 100FPS). Until now there was 1 "slot" for a mouse-cursor grab force. Affectors are an extension of this system - you can add multiple forces this way and control them in various ways. The mouse grab system was remade using affectors. Planned features (general status: alpha version):

• uniform force affector - applies constant force in constant direction to nodes. Status: stub, no scripting.
• pinned force affector - pulls nodes towards a given point. Status: working (used in mouse grab), scripting not tested.
• thruster affector - applies force within a frame of reference given by nodes noderef/nodex/nodey, like aeroengines/screwprops. Status: stub.
• live editing - use MSG_EDI_ADD/REMOVE_AFFECTOR_REQUESTED with arguments-struct. This works (used in mouse grab).
• script editing - call game.pushMessage(MSG_EDI_ADD/REMOVE_AFFECTOR_REQUESTED, {}) with a dictionary of params. Status: ADD is coded but not tested, REMOVE isn't coded yet.
• force pinning with INSERT - an extension to grab mode. Use right mouse button to unpin again. This works, see GIF below.
• theme editor UI - because the debug views get more complex and color definitions are hardcoded all over the place. And while I'm consolidating it, it's a small job to do a theme editor. Status: stub, not usable yet.

[ohlidalp]

Closing this in favor of the superior FreeForces: #3159.

I will create a separate PR for the mouse-grab node highlight, that feature deserves another chance.