/// <summary>
/// Finds what vertices of the geometry that is inside the fluidcontainer
/// </summary>
/// <param name="geom">The geometry to check against</param>
private void FindVerticesInFluid(Geom geom)
{
_vertices.Clear();
for (int i = 0; i < geom.worldVertices.Count; i++)
{
_vert = geom.worldVertices[i];
if (_fluidContainer.Contains(ref _vert))
{
_vertices.Add(_vert);
}
}
}
public override void Update(float dt)
{
_fluidContainer.Update(dt);
for (int i = 0; i < _geomList.Count; i++)
{
Fixture fixture = _geomList[i];
Body body = fixture.Body;
Vertices localVertices = fixture.Shape.GetVertices();
_totalArea = fixture.Shape.Area;
//If the AABB of the geometry does not intersect the fluidcontainer
//continue to the next geometry
AABB aabb;
fixture.Shape.ComputeAABB(out aabb, ref fixture.Body._xf, 0);
if (!_fluidContainer.Intersect(ref aabb))
{
continue;
}
//Find the vertices contained in the fluidcontainer
_vertices.Clear();
for (int k = 0; k < localVertices.Count; k++)
{
_vert = fixture.Body.GetWorldPoint(localVertices[k]);
if (_fluidContainer.Contains(ref _vert))
{
_vertices.Add(_vert);
}
}
//The geometry is not in the fluid, up til a certain point.
if (_vertices.Count < localVertices.Count * 0.15f)
{
_geomInFluidList[fixture] = false;
}
_area = _vertices.GetArea();
if (_area < .0001)
{
continue;
}
_centroid = _vertices.GetCentroid();
//Calculate buoyancy force
_buoyancyForce = -_gravity * (_area * fixture.Shape.Density) * Density;
//Calculate linear and rotational drag
_centroidVelocity = fixture.Body.GetLinearVelocityFromWorldPoint(_centroid);
_axis.X = -_centroidVelocity.Y;
_axis.Y = _centroidVelocity.X;
//can't normalize a zero length vector
if (_axis.X != 0 || _axis.Y != 0)
{
_axis.Normalize();
}
_vertices.ProjectToAxis(ref _axis, out _min, out _max);
_dragArea = Math.Abs(_max - _min);
_partialMass = fixture.Body.Mass * (_area / _totalArea);
_linearDragForce = -.5f * Density * _dragArea * LinearDragCoefficient * _partialMass * _centroidVelocity;
_rotationalDragTorque = -fixture.Body.AngularVelocity * AngularDragCoefficient * _partialMass;
//Add the buoyancy force and lienar drag force
Vector2.Add(ref _buoyancyForce, ref _linearDragForce, out _totalForce);
//Apply total force to the body
body.ApplyForce(ref _totalForce);
//Apply rotational drag
body.ApplyTorque(_rotationalDragTorque);
if (_geomInFluidList[_geomList[i]] == false)
{
//The geometry is now in the water. Fire the Entry event
_geomInFluidList[_geomList[i]] = true;
if (Entry != null)
{
Entry(_geomList[i], _vertices);
}
}
}
}