BEPUphysics

a) I created a sphere (entity) holding my 3D ball (model) and cylinders that contain the 3d soccer goal. Why the ball collides with a cylinder only if kicked low shot (and not in air)?

I apply an arbitrary impulse (Is it right?) to the ball when kicked.

b) the ball trajectory after it slammed on the soccer ball pole is changed by BEPU automatically, right?

c) Should I create a goalkepper that dives: the animation is done in software modeling? How to manage collisions of an animated 3D model?

By the way, those cylinders are huge. The default scale interpretation likes objects to be somewhere in the range of 0.5 to 10 units. It's possible to go outside of this range, but if you go too far (thousands upon thousands of units), numerical issues can start to crop up. If you happen to see such issues, you can address them by either normalizing the scale of the simulation to the default scale interpretation or retuning BEPUphysics to understand the larger simulation. Examples of this retuning can be found in the ScaleDemo and ConfigurationHelper.ApplyScale of the BEPUphysicsDemos project in the main source download.

It would be a good idea to approximate the character; performing collision detection on every triangle in a character model would be a large waste of time. The movement of a character could be handled with something like the CharacterController from the BEPUphysicsDemos. The CharacterController is a single cylinder, so it would probably be a good idea to use CollisionRules to prevent the ball from hitting the character cylinder. This means the character cylinder is just used for the character's interaction with the environment and other players. To block the ball, you could position kinematic entities according to the current animation of the character; these entities could be made to only collide with the ball. This lets the pose of the character describe how it blocks incoming balls. On the other hand, this may be way too much detail for the game, and just using the CharacterController's main cylinder with perhaps an extra big blocker or something would be sufficient.
Norbo
Site Admin

Posts: 2970
Joined: Tue Jul 04, 2006 5:45 am

Is it ok?

And if goalkeeper dives left, cylinder moves automatically with animation play? Or do I have to move the cylinder through code?

I must see SimpleCharacterController or CharacterController?

CharacterController = new SphereCharacterController(new Vector3(0, 0, -11f), 1.5f,100f);
                bodyMover = new EntityMover( CharacterController.Body);
                CharacterController.Body.BecomeKinematic();
                
                space.Add(CharacterController);
                space.Add(bodyMover);
                modeldude = new EntityModel(CharacterController.Body, content.Load<Model>("GoalkeeperLeftAnim"), Matrix.Identity);
                CharacterController.Body.Tag = modeldude;
               
                SkinningData skinningData = modeldude.model.Tag as SkinningData;

                if (skinningData == null)
                    throw new InvalidOperationException
                        ("This model does not contain a SkinningData tag.");

                // Create an animation player, and start decoding an animation clip.
                animationPlayer = new AnimationPlayer(skinningData);

                AnimationClip clip = skinningData.AnimationClips["Take 001"];

                animationPlayer.StartClip(clip);

          animationPlayer.Update(gameTime.ElapsedGameTime, true, Matrix.Identity);

            bodyMover.TargetPosition = bodyMover.Entity.Position +new Vector3(-0.1f,0f,0f);

Norbo wrote:

Is it ok?

That's the rough outline, yup.

And if goalkeeper dives left, cylinder moves automatically with animation play? Or do I have to move the cylinder through code?

The entities must be controlled directly. The physics engine, by itself, has no concept of graphics; any association between graphics and physics must be directly handled.

The entities representing the body could be created in the 'bind pose' of the character and associated with certain animation bones by a transform. When the character moves, the entities would be moved according to the animation bones and the transform associated with the entity. So, if localTransform is the transform from the animation bone to the entity, the world space location of the entity would be the localTransform * animationBoneWorldTransform.

To actually move the entities, it would be a good idea to use velocities instead of teleportation alone. This allows collision response to work correctly. The EntityMover and EntityRotator are a couple of simple convenience classes which will compute the velocities to apply to a kinematic entity given a position/orientation goal for you.

I must see SimpleCharacterController or CharacterController?

The CharacterController and SphereCharacterController are substantially better than the SimpleCharacterController. The SphereCharacterController is a sphere and doesn't support stepping, but if the character body is only colliding with the environment, it might not matter that it's a sphere.

Finally, how can I associate sphere to a single bone? If my bone's name Tom, must I refer to "Tom"? And how can I capture Tom position (position change continuously in animation fbx)?

Why must I use SphereCharacterController? Can I create 5 simple sphere (body, legs and arms) to wrap my character? (Whereas my animations are preloaded in fbx files!)