Skipping the simulation, switching off collisions, and other approaches were not correct as they either broke some mods, or some core mechanics of the engine such as teleportation or waterwalking. As it turns out, the way to go is to simply do _nothing_ (modulo some gymnastics to account for the 1 frame difference in case of async).
Scripted movement and the unstucking logic tends to collide. Early out of unstuck in case the actor doesn't attempt to move. This means there is no AI package for NPC, which are the case for some boats and striders, or the player is content with their position.
1) As much as I dislike it, upping the collision margin from 0.1 to 0.2
fixes bugs, particularly involving walking into upwards-slanted walls.
2) There were still some problems involving acute crevices/seams; they
were using the adjusted instead of unadjusted normal, and also they need
to bypass the don't-slide-upwards check to prevent (see #6379)
3) The move-away-from-what-we-just-hit code needs to run always, not
just on non-initial iterations. No idea why I did it this way before.
4) Force bullet to give actor boxes a tiny collision margin of 0.001
instead of the default 0.04. I can't tell whether this is actually
working or not, but it should reduce unexplained weirdness.
5) A piece of code that was meant to prevent bugs by short-circuiting
the movement solver if its direction changed more than 180 degrees
actually caused problems instead of preventing them, so I deleted it.
MWWorld::Ptr:
- they are equivalent
- btCollisionObject* is readily available from the simulation, it saves
a call to a mutex
- btCollisionObject* is smaller
- compute the swimming state instead of storing it, it changes as part of the simulation and was not updated, so it was wrong anyway.
- store the swim level in ActorFrameData, it is constant per Actor so no need to compute it inside the simulation
ActActorFrameData structure. It makes it easier to reason about the
simulation (and hopefully simplify it).
Remove atomics from Actor class as a side effect.
Rename mFloatToSurface to mInert to make is explicit what it represent, not what it is used for
Store the Actor rotation (1 Vec2) instead of the whole ESM::Position (2 Vec3)
projectile collision shape.
A side effect of moving actors outside of projectile collision shape is that if both the actor and the projectile are
near a wall, the actor could get moved outside of the world.
Change order of traversal simulation step to make it rare enough to be parallelizable
Before:
for actor in actors:
repeat numstep:
solve(actor)
After:
repeat numstep:
for actor in actors:
solve(actor)
Introduce struct ActorFrameData to pack all data that is necessary for
the solver
