protected override Vector3d CalculateDesiredVelocity()
{
Vector3d nrml = environment.ClosestNormal(particle.Position3D);
Vector3d drainVec = Vector3d.CrossProduct(nrml, Vector3d.ZAxis);
drainVec.Unitize();
drainVec.Transform(Transform.Rotation(Math.PI * angle, nrml, particle.Position3D));
drainVec = drainVec * stepDistance;
if (environment.GetType() == typeof(SurfaceEnvironmentType))
{
Point3d pt2D = particle.Position3D;
pt2D.Transform(Transform.Translation(drainVec));
pt2D = environment.MapTo2D(pt2D);
drainVec = Util.Vector.Vector2Point(particle.Position, pt2D);
}
return(drainVec);
}
