Review planet physics

[DaloLorn]

This is technically only noticeable in mods that mess with galaxy scaling, but it's possible for a planet's hitbox to overlap with stations or other planets. This can theoretically allow them to become immune to any non-AoE attack (except maybe Disruptors), as all projectiles just collide with the planet instead.

To resolve this, objects inside a planet should be kicked out somehow. (Unless the planet has physics disabled, like Ringworlds.)

[DaloLorn]

• Planets cannot be closer than (combined planet radius + combined orbital radius) under any circumstance. (Unless their physics has been disabled, like Ringworlds.)
• Orbiting objects cannot be inside whatever they are orbiting.
• Certain objects (like Remnant Defense Stations) are treated as planets for the purposes of blocking planets. These objects cannot be bumped out of position, and will instead force-bump the incoming planet away. (If they have a support circle, its radius is used as a substitute for a planet's orbital radius.)
• Remnant Defense Stations cannot enter orbit of a planet (if this is not already the case).

[DaloLorn]

Mover component is responsible for all collision physics. Planets are traditionally exempt from collisions, but should be made subject to collisions with other stellar bodies. May require a new Collider component to cover all collidable objects without force-activating movers on planets that don't have them - seems safer that way.

Collider component could then handle everything in one neat package. LeaderAI.getFormationRadius() can be used to compute the orbital/support radius of any object that needed bumping. (All leader objects should try to be at least that far from planets, maybe? Objects without movers definitely should.)

• Objects whose Colliders have been flagged as immovable (NOTE: These should be actually immovable objects, like stars, Remnant Defense Stations, etc., lest they become unstoppable forces instead!) cannot be bumped by anything.
• Planets are only bumped by other planets and immovable objects. When this happens, they are bumped out to the planet's orbital radius plus the bumping object's support radius (if any).
• As a general rule, larger objects bump smaller objects. This is only overruled by immovable objects (which bump everything) and planet-nonplanet interactions (planet bumps all other movable objects).
• In collisions with planets and immovables, objects without movers (not the same as immovable objects!) are bumped out to their support radius.
• All other collisions are as normal.

[Skeletonxf]

Have you had any ideas regarding detecting collisions? It would be possible to place a station/orbital/ship just within the acceptable min distances such that it doesn't need bumping, and then retrofit/upgrade said object so that it has a bigger formation radius. I presume we cannot afford to recheck all objects with all others on every tick, so most likely we'd want to do these bump checks after an object finishes moving (but what about never ending motion? In CE playing as battleworlders it would be quite easy to order two planets to endlessly move around each other in a loop), but also we may need some kind of delta that rare things like retrofits could trigger so we catch cases where an object becomes bigger without moving.

[DaloLorn]

The existing collision code (currently running on mover tick) seems adequate, it just needs to be expanded with a few new rules regarding bumpability. (Planets, for instance, don't currently make any collision checks of their own when they're normally orbiting, which is one of the rules that needs to change.)