public RollingSphereSample(Microsoft.Xna.Framework.Game game)
: base(game)
{
// To demonstrate the problems with triangle meshes we increase the gravity and let a
// sphere roll over a curved surface.
// Add basic force effects.
Simulation.ForceEffects.Add(new Gravity { Acceleration = new Vector3F(0, -30, 0) }); // Higher gravity to make the problem more visible.
Simulation.ForceEffects.Add(new Damping());
// Use the custom contact filter to improve sphere contacts.
_sphereContactFilter = new SphereContactFilter();
Simulation.CollisionDomain.CollisionDetection.ContactFilter = _sphereContactFilter;
// The triangle mesh could be loaded from a file, such as an XNA Model.
// In this example will create a height field and convert the height field into a triangle mesh.
var numberOfSamplesX = 60;
var numberOfSamplesZ = 10;
var samples = new float[numberOfSamplesX * numberOfSamplesZ];
for (int z = 0; z < numberOfSamplesZ; z++)
for (int x = 0; x < numberOfSamplesX; x++)
samples[z * numberOfSamplesX + x] = (float)(Math.Sin(x / 6f) * 10f + 5f);
var heightField = new HeightField(0, 0, 70, 30, samples, numberOfSamplesX, numberOfSamplesZ);
// Convert the height field to a triangle mesh.
ITriangleMesh mesh = heightField.GetMesh(0.01f, 3);
// Create a shape for the triangle mesh.
_triangleMeshShape = new TriangleMeshShape(mesh);
// Enable contact welding. And set the welding limit to 1 for maximal effect.
_triangleMeshShape.EnableContactWelding = true;
_originalWeldingLimit = TriangleMeshAlgorithm.WeldingLimit;
TriangleMeshAlgorithm.WeldingLimit = 1;
// Optional: Assign a spatial partitioning scheme to the triangle mesh. (A spatial partition
// adds an additional memory overhead, but it improves collision detection speed tremendously!)
_triangleMeshShape.Partition = new CompressedAabbTree() { BottomUpBuildThreshold = 0 };
// Create a static rigid body using the shape and add it to the simulation.
// We explicitly specify a mass frame. We can use any mass frame for static bodies (because
// static bodies are effectively treated as if they have infinite mass). If we do not specify
// a mass frame in the rigid body constructor, the constructor will automatically compute an
// approximate mass frame (which can take some time for large meshes).
var ground = new RigidBody(_triangleMeshShape, new MassFrame(), null)
{
Pose = new Pose(new Vector3F(-34, 0, -40f)),
MotionType = MotionType.Static,
};
Simulation.RigidBodies.Add(ground);
SphereShape sphereShape = new SphereShape(0.5f);
_sphere = new RigidBody(sphereShape);
Simulation.RigidBodies.Add(_sphere);
_enableSmoothMovement = true;
_timeUntilReset = TimeSpan.Zero;
}
public TriangleMeshSample(Microsoft.Xna.Framework.Game game)
: base(game)
{
// Add basic force effects.
Simulation.ForceEffects.Add(new Gravity());
Simulation.ForceEffects.Add(new Damping());
// The triangle mesh could be loaded from a file, such as an XNA Model.
// In this example will use the same height field as in Sample11 and convert
// the shape into a triangle mesh.
var numberOfSamplesX = 20;
var numberOfSamplesZ = 20;
var heights = new float[numberOfSamplesX * numberOfSamplesZ];
for (int z = 0; z < numberOfSamplesZ; z++)
for (int x = 0; x < numberOfSamplesX; x++)
heights[z * numberOfSamplesX + x] = (float)(Math.Cos(z / 2f) * Math.Sin(x / 2f) * 5f + 5f);
HeightField heightField = new HeightField(0, 0, 100, 100, heights, numberOfSamplesX, numberOfSamplesZ);
// Convert the height field to a triangle mesh.
ITriangleMesh mesh = heightField.GetMesh(0.01f, 3);
// Create a shape for the triangle mesh.
TriangleMeshShape triangleMeshShape = new TriangleMeshShape(mesh);
// Optional: We can enable "contact welding". When this flag is enabled, the triangle shape
// precomputes additional internal information for the mesh. The collision detection will
// be able to compute better contacts (e.g. better normal vectors at triangle edges).
// Pro: Collision detection can compute better contact information.
// Con: Contact welding information needs a bit of memory. And the collision detection is
// a bit slower.
triangleMeshShape.EnableContactWelding = true;
// Optional: Assign a spatial partitioning scheme to the triangle mesh. (A spatial partition
// adds an additional memory overhead, but it improves collision detection speed tremendously!)
triangleMeshShape.Partition = new CompressedAabbTree
{
// The tree is automatically built using a mixed top-down/bottom-up approach. Bottom-up
// building is slower but produces better trees. If the tree building takes too long,
// we can lower the BottomUpBuildThreshold (default is 128).
BottomUpBuildThreshold = 0,
};
// Optional: The partition will be automatically built when needed. For static meshes it is
// built only once when it is needed for the first time. Building the AABB tree can take a
// few seconds for very large meshes.
// By calling Update() manually we can force the partition to be built right now:
//triangleMeshShape.Partition.Update(false);
// We could also call this method in a background thread while the level is loading. Or,
// we can build the triangle mesh and the AABB tree in the XNA content pipeline and avoid the
// building of the tree at runtime (see Sample 33).
// Create a static rigid body using the shape and add it to the simulation.
// We explicitly specify a mass frame. We can use any mass frame for static bodies (because
// static bodies are effectively treated as if they have infinite mass). If we do not specify
// a mass frame in the rigid body constructor, the constructor will automatically compute an
// approximate mass frame (which can take some time for large meshes).
var ground = new RigidBody(triangleMeshShape, new MassFrame(), null)
{
Pose = new Pose(new Vector3F(-50, 0, -50f)),
MotionType = MotionType.Static,
};
Simulation.RigidBodies.Add(ground);
// Distribute a few spheres and boxes across the landscape.
SphereShape sphereShape = new SphereShape(0.5f);
for (int i = 0; i < 30; i++)
{
Vector3F position = RandomHelper.Random.NextVector3F(-30, 30);
position.Y = 20;
RigidBody body = new RigidBody(sphereShape)
{
Pose = new Pose(position),
};
Simulation.RigidBodies.Add(body);
}
BoxShape boxShape = new BoxShape(1, 1, 1);
for (int i = 0; i < 30; i++)
{
Vector3F position = RandomHelper.Random.NextVector3F(-30, 30);
position.Y = 20;
RigidBody body = new RigidBody(boxShape)
{
Pose = new Pose(position),
};
Simulation.RigidBodies.Add(body);
}
}