Character Controller inconsistencies

[sooms]

I've now got my world running Bullet physics and it's looking pretty good (yay) but there is 1 issue that I am noticing - inconsistencies with the kinematic character controller. This has displayed itself in two ways.

1) Jump - the speed of the fall of the jump seems to be based on framerate. The higher my framerate the faster I drop back down. I have played around a little with the timestep stuff but haven't seen any change.

2) Character movement speed - for some reason the first world I log into seems to have an effect on the characters movement speed. If I log into world A first my character goes twice as fast as he should, but if I log into world B first the speed seems right. What is extra odd though is that if I teleport to the other world then my characters speed stays consistent with whatever world I logged into first. It's only when I first start up the client and initialise the physics system that the speed changes.

I can understand people may have trouble understanding this world idea, so to elaborate a bit: When changing worlds the physics system isn't changed, and neither is the character. All that occurs is that all the objects in the scene get cleared away then new ones are loaded. The character may be moved to a new position, and that is achieved by using the Warp() function.

There is a slight fps difference between the worlds when first logging in (one has more objects than the other) but that shouldn't make a difference should it?


Anyway I know it's always easier to see some code to go with it so here is my world initialisation code:

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            collisionShapes = new AlignedCollisionShapeArray();
            collisionObjects = new AlignedCollisionObjectArray();
            configuration = new DefaultCollisionConfiguration();
            dispatcher = new CollisionDispatcher(configuration);
            broadphase = new DbvtBroadphase();
            solver = new SequentialImpulseConstraintSolver();
            world = new DiscreteDynamicsWorld(dispatcher, broadphase, solver, configuration);
            ghostCallback = new GhostPairCallback();
            world.Broadphase.OverlappingPairCache.SetInternalGhostPairCallback(ghostCallback);
            //float timeStep = 1.0f / (3 * 20);
            //world.DispatchInfo.TimeStep = timeStep;
            world.DispatchInfo.AllowedCcdPenetration = 0.0001f;
            //world.Gravity = new Vector3(0, gravity, 0);
            mobControllers = new Dictionary<SceneNode, BulletSharpMobState>();
            initialized = true;

Character controller creation code:

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            ConvexShape capsule = new CapsuleShape(radius, modelHeight - radius * 2);
            ghostObject = new PairCachingGhostObject();
            Vector3 position = new Vector3(characterNode.Position.x / scaleFactor, (characterNode.Position.y.Ceiling() + 1500) / scaleFactor, characterNode.Position.z / scaleFactor);
            Matrix4 worldTransform = Matrix4.Compose(position, Vector3.UnitScale, Quaternion.Identity);
            ghostObject.WorldTransform = worldTransform;
            ghostObject.CollisionShape = capsule;
            ghostObject.CollisionFlags = CollisionFlags.CharacterObject;
            playerController = new KinematicCharacterController(ghostObject, capsule, 350f / scaleFactor, 1);
            //playerController.SetFallSpeed(0);
            playerController.SetJumpSpeed(8);
            playerController.SetMaxJumpHeight(1);
            characterToLoad = null;
            BulletSharpMobState mobMovementState = new BulletSharpMobState(playerController, mobNodePositionUpdate, modelHeight / 2, userData);
            mobMovementState.JumpEvent += jumpHandler;
            mobMovementState.FallEvent += fallHandler;
            mobControllers.Add(characterNode, mobMovementState);
            world.AddCollisionObject(ghostObject, CollisionFilterGroups.CharacterFilter, CollisionFilterGroups.StaticFilter | CollisionFilterGroups.DefaultFilter);
            world.AddAction(playerController);
            collisionShapes.Add(capsule);
            collisionObjects.Add(ghostObject);

And the code to handle movement requests and step the simulation (this is called each frame):

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playerController.SetWalkDirection(desiredDisplacement);
            float timeStep = 1.0f / (3 * 20);
            //world.StepSimulation(timeSinceLastFrame / 1000, 1, timeStep);
            world.StepSimulation(timeSinceLastFrame / 1000);
            // Check if player is on ground
            mobControllers[sceneNode].OnGround = playerController.OnGround;
            // Get the players current position
            Matrix4 worldTransform = (Matrix4)playerController.GhostObject.WorldTransform;
            pos = worldTransform.Translation;

The commented out parts show you things I have tried. Thanks in advance for any help getting this sorted.

Andrew.

[N_K]

I'm surprised I'm not the only one who experimented with the character controller. But as far as I managed to get, it seems to be incomplete, and not ready for pratical use at all.

So, I think, the best thing you could do right is not to use it at all, and make your own character controller from scracth. Or wait for the official one to be finished.

Expert opinions about these problems would be welcome, of course, but it seems that this forum is deserted.

[frank28_nfls]

1) Jump - the speed of the fall of the jump seems to be based on framerate. The higher my framerate the faster I drop back down. I have played around a little with the timestep stuff but haven't seen any change.

I also notice some problem when falling, however, not during jump, and the problem is not framerate related. I suggest to use "setVelocityForTimeInterval" instead of "setWalkDirection"(see below), and see if your problem still exists.

2) Character movement speed

And the code to handle movement requests and step the simulation (this is called each frame):

Code: Select all

playerController.SetWalkDirection(desiredDisplacement);
            float timeStep = 1.0f / (3 * 20);
            //world.StepSimulation(timeSinceLastFrame / 1000, 1, timeStep);
            world.StepSimulation(timeSinceLastFrame / 1000);
            // Check if player is on ground
            mobControllers[sceneNode].OnGround = playerController.OnGround;
            // Get the players current position
            Matrix4 worldTransform = (Matrix4)playerController.GhostObject.WorldTransform;
            pos = worldTransform.Translation;

The commented out parts show you things I have tried.

I see you comment out "//world.StepSimulation(timeSinceLastFrame / 1000, 1, timeStep);", and am curious that you still saw problem for movement? It should be fine to limit only one update for the simulation in every frame, with use of "setWalkDirection", according to my understanding of that code. However, I gave a suggestion in another post: http://bulletphysics.org/Bullet/phpBB3/ ... 254#p28333 to use "setVelocityForTimeInterval" instead. See if it works for you.

[lenti]

If the forum is deserted, where did everyone go?

[MaxDZ8]

I guess most people is busy and cannot afford frequent checks.
Back to the problem, I have also experienced the effects you roughly describe.
Odds are the default controller will never get finished, as it is application dependent and even context-dependent.

For example, in the game I'm doing now, I have full air control (which would be nonsense), a powerup to allow double-jump is planned as well as another one to climb up steep slopes.
I am still working on this - more advanced levels appear to be a consistent challenge - so I'm myself not well aware of the correctness of what I'm doing. But I look forward in some cooperation.