|
|
@@ -411,6 +411,26 @@ Fast rotating long objects are also to be avoided, as the LinearCast motion qual
|
|
|
|
|
|
|
|
|
|
|
|
+# Character Controllers {#character-controllers}
|
|
|
+
|
|
|
+The [Character](@ref Character) and [CharacterVirtual](@ref CharacterVirtual) classes can be used to create a character controller. These are usually used to represent the player as a simple capsule or tall box and perform collision detection while the character navigates through the world.
|
|
|
+
|
|
|
+The Character class is the simplest controller and is essentially a rigid body that has been configured to only allow translation (and no rotation so it stays upright). It is simulated together with the other rigid bodies so it properly reacts to them. Because it is simulated, it is usually not the best solution for a player as the player usually requires a lot of behavior that is non-physical. This character controller is cheap so it is recommended for e.g. simple AI characters. After every PhysicsSystem::Update call you must call Character::PostSimulation to update the ground contacts.
|
|
|
+
|
|
|
+The CharacterVirtual class is much more advanced. It is implemented using collision detection functionality only (through NarrowPhaseQuery) and is simulated when CharacterVirtual::Update is called. Since the character is not 'added' to the world, it is not visible to rigid bodies and it only interacts with them during the CharacterVirtual::Update function by applying impulses. This does mean there can be some update order artifacts, like the character slightly hovering above an elevator going down, because the characters moves at a different time than the other rigid bodies. Separating it has the benefit that the update can happen at the appropriate moment in the game code. Multiple CharacterVirtuals can update concurrently, so it is not an issue if the game code is parallelized.
|
|
|
+
|
|
|
+CharacterVirtual has the following extra functionality:
|
|
|
+* Sliding along walls
|
|
|
+* Interaction with elevators and moving platforms
|
|
|
+* Enhanced steep slope detection (standing in a funnel whose sides are too steep to stand on will not be considered as too steep)
|
|
|
+* Stair stepping through the CharacterVirtual::ExtendedUpdate call
|
|
|
+* Sticking to the ground when walking down a slope through the CharacterVirtual::ExtendedUpdate call
|
|
|
+* Support for specifying a local coordinate system that allows e.g. [walking around in a flying space ship](https://github.com/jrouwe/JoltPhysics/blob/master/Samples/Tests/Character/CharacterSpaceShipTest.cpp) that is equipped with 'inertial dampers' (a sci-fi concept often used in games).
|
|
|
+
|
|
|
+If you want CharacterVirtual to have presence in the world, it is recommended to pair it with a slightly smaller [Kinematic](@ref EMotionType) body (or Character). After each update, move this body using BodyInterface::MoveKinematic to the new location. This ensures that standard collision tests like ray casts are able to find the character in the world and that fast moving objects with motion quality [LinearCast](@ref EMotionQuality) will not pass through the character in 1 update. As an alternative to a Kinematic body, you can also use a regular Dynamic body with a [gravity factor](@ref BodyCreationSettings::mGravityFactor) of 0. Ensure that the character only collides with dynamic objects in this case. The advantage of this approach is that the paired body doesn't have infinite mass so is less strong.
|
|
|
+
|
|
|
+To get started take a look at the [Character](https://github.com/jrouwe/JoltPhysics/blob/master/Samples/Tests/Character/CharacterTest.cpp) and [CharacterVirtual](https://github.com/jrouwe/JoltPhysics/blob/master/Samples/Tests/Character/CharacterVirtualTest.cpp) examples.
|
|
|
+
|
|
|
# The Simulation Step {#the-simulation-step}
|
|
|
|
|
|
The simulation step [PhysicsSystem::Update](@ref PhysicsSystem::Update) uses jobs ([JobSystem](@ref JobSystem)) to perform the needed work. This allows spreading the workload across multiple CPU's. We use a Sequential Impulse solver with warm starting as described in [Modeling and Solving Constraints - Erin Catto](https://box2d.org/files/ErinCatto_ModelingAndSolvingConstraints_GDC2009.pdf)
|
Jorrit Rouwe