Previous MR change the meaning of mPositionOffset: it is now just a log
of relative movement that were already applied to allow the physics
simulation to catch up, instead of changes that needs to be applied. As
such, after a teleport we need to reset it. Also, since mWorldPosition
is already with the offset we should not update its value in
applyPositionOffset().
Instead of registering the desired change of position and rely on
physics simulation to apply it to the world, immediately change the
position in the world without reset the simulation.
When a script calls SetPos for x,y,z in sequence on an actor, we need to make sure
that the actor will not spawn under ground at x,y coordinates.
Now that change of coordinates are cumulated and applied all at once, we
need to account for the whole offset.
To this end move the terrain height check inside of Actor class.
To make SetPos works with async physics, it was modified to register a
position offset that would be applied to the real position during the
simulation.
A common pattern to teleport NPC in scripts is a sequence of SetPos/Disable/Enable in the same frame.
Since Disable/Enable creates a new physics actor using last known
RefData::Position, the registered offset never get a chance to be applied.
Modify disable() to call moveObject with the offset applied, so that the newly created physics actor will have up-to-date position
When a position is forced, the actor position in physics subsystem is
overriden. The background physics thread is not made aware of this,
its result are simply discarded.
There is a short window where this doesn't work (in this
example, actor is at A and script moves it to B)
1) actor position is set to B. (among others, Actor::mPosition is set to B)
2) physics thread reset Actor::mPosition with stale value (around A)
3) main thread read simulation result, reset Actor::mSkipSimulation flag => actor is at B
4) physics thread fetch latest Actor::mPosition value, which is around A
5) main thread read simulation result, actor is around A
To avoid this situation, do not perform 2) until after 3) occurs. This
way, at 4) starts the simulation with up-to-date Actor::mPosition
One of the issue since the introduction of async physics is the quirky
handling of scripted moves. Previous attempt to account for them was
based on detecting changes in actor position while the physics thread is
running. To this end, semantics of Actor::updatePosition() (which is
responsible for set the absolute position of an actor in the world) was
toned down to merely store the desired position, with the physics system
actually responsible for moving the actor. For the cases were complete
override of the physics simulation was needed, I introduced
Actor::resetPosition(), which actually have same semantics as
original updatePosition(). This in turn introduced a loads of new bugs
when the weakened semantics broke key assumptions inside the engine
(spawning, summoning, teleport, etc).
Instead of tracking them down, count on the newly introduced support for
object relative movements in the engine (World::moveObjectBy) to
register relative movements and restore original handling of absolute positionning.
Changes are relatively small:
- move resetPosition() content into updatePosition()
- call updatePosition() everywhere it was called before
- remove all added calls to the now non-existing resetPosition()
tldr; ditch last month worth of bug introduction and eradication and redo
it properly
This gives finer control over reseting positions (switch off tcl is no
longer glitchy) and solve most of the erroneous usage of stale World::Ptr
indicated by:
"Error in frame: moveTo: object is not in this cell"
its current position.
Use it in relevant MWScripts opcode (move and moveworld).
Remove the fragile detection of scripted translation from PhysicsTaskScheduler.
No user visible change, just a more robust mechanism.
be sure the simulation is over. Otherwise, if the simulation is too slow
the position is wrong, and the actors would jump back and forth between
old and new position instead of actually moving.
Before this change, if an actor position was changed while the physics
simulation was running, the simulation result would be discarded. It is
fine in case of one off event such as teleport, but in the case of
scripts making use of this functionality to make lifts or conveyor (such
as Sotha Sil Expanded mod) it broke actor movement.
To alleviate this issue, at the end of the simulation, the position of the Actor
in the world is compared to the position it had at the beginning of the
simulation. A difference indicate a force move occured. In this case,
the Actor mPosition and mPreviousPosition are translated by the difference of position.
Since the Actor position will be really set while the next simulation runs, we
save it in the mNextPosition field.
Before movement calculation, the main thread prepare a
vector of ActorFrameData, which contains all data necessary to perform
the simulation, and feed it to the solver. At the same time it fetches
the result from the previous background simulation, which in turn is
used by the game mechanics.
Other functions of the physics system (weapon hit for instance)
interrupt the background simulation, with some exceptions described
below.
The number of threads is controlled by the numeric setting
[Physics]
async num threads
In case 'async num threads' > 1 and Bullet doesn't support multiple threads,
1 async thread will be used. 0 means synchronous solver.
Additional settings (will be silently switched off if async num threads = 0)
[Physics]
defer aabb update
Update AABBs of actors and objects in the background thread(s). It is not an especially
costly operation, but it needs exclusive access to the collision world, which blocks
other operations. Since AABB needs to be updated for collision detection, one can queue
them to defer update before start of the movement solver. Extensive tests on as much
as one installation (mine) show no drawback having that switched on.
[Physics]
lineofsight keep inactive cache
Control for how long (how many frames) the line of sight (LOS) request will be kept updated.
When a request for LOS is made for the first time, the background threads are stopped to
service it. From now on, the LOS will be refreshed preemptively as part of the background
routine until it is not required for lineofsight keep inactive cache frames. This mean
that subsequent request will not interrupt the background computation.
The cylinder base is no longer appropriate as of the change to capsules.
This also works around a bug when tracing a small cylinder/box shape apparently introduced with bullet 2.86.
Previously we were handling 'on slope' synonymously with 'in air' which caused some odd effects.
Practical changes:
- Sliding down a slope no longer applies fall damage.
- Fixed a climbing exploit that would allow climbing steep slopes with repeated use of the Jump function.
