public void TestLaw2()
{
var context = new PhysicalContext <int>(1, 2);
context.AddEntity(0, new PointMass(1, 1, 1, 0));
context.AddEntity(1, new PointMass(1, 1, 2, 0));
var law = HookesLaw.GetLaw(1, 0, undeformedDistance: 0, elasticityCoefficient: 1);
AreEqual(new Force(0, 0, -1), law(context));
law = HookesLaw.GetLaw(1, 0, undeformedDistance: 3, elasticityCoefficient: 2);
AreEqual(new Force(0, 0, 4), law(context));
law = HookesLaw.GetLaw(1, 0, undeformedDistance: 12, elasticityCoefficient: 0);
AreEqual(new Force(0, 0, 0), law(context));
}
public void TestLaw1()
{
var context = new PhysicalContext <int>(1, 2);
context.AddEntity(0, new PointMass(0, 0, 0, 0));
context.AddEntity(1, new PointMass(3, 4, 0, 0));
var law = HookesLaw.GetLaw(1, 0, undeformedDistance: 5, elasticityCoefficient: 1);
AreEqual(new Force(0, 0, 0), law(context));
law = HookesLaw.GetLaw(1, 0, undeformedDistance: 10, elasticityCoefficient: 1);
AreEqual(new Force(3, 4, 0), law(context));
law = HookesLaw.GetLaw(1, 0, undeformedDistance: 10, elasticityCoefficient: 2);
AreEqual(new Force(6, 8, 0), law(context));
law = HookesLaw.GetLaw(1, 0, undeformedDistance: 0, elasticityCoefficient: 0.1);
AreEqual(new Force(-0.3, -0.4, 0), law(context));
}
static void Main(string[] args)
{
//PhysicalContext is the core class represents set of entities and
//set of force evaluation laws binded to it.
//Type parameter represents the type of keys used to adding and retrieving entities.
var context = new PhysicalContext <string>
(
timePerTick: dt, //The time, that is considered to be as small, as force values are uniform.
//The smaller timePerTick is, the better precision we get.
//Be aware, time for evaluating state of entities after certain period of time
//is proportional to (timePerTick)^-1.
capacity: 1 //Number of entities required to be added to context.
);
//Adding entity
var freeFallEntity = new PointMass
(
x: new AxisStatus(3.4), //Position = 3.4, zero velocity
y: new AxisStatus(0, 10), //Zero position, velocity = 10
z: new AxisStatus(1.1, 2), //Position = 1.1, Velocity = 2
mass: 77.7
);
context.AddEntity
(
"freeFallEntity", //key
freeFallEntity, //entity
c => //Only force that have impact on this entity
- new Force
(
xComponent: 0,
yComponent: c["freeFallEntity"].Mass * freeFallAcceleration,
zComponent: 0
)
//This force is always vertical and equal to mass of entity multiplied
//by free fall acceleration.
);
Console.WriteLine($"Start state is \n{context["freeFallEntity"]}");
//Evaluating the state of context after 1 second.
context.Tick(timeSpan: 1);
Console.WriteLine($"\nState of entity after 1 second is \n{context["freeFallEntity"]}");
//If you want to record some data while context is updating,
//you may subscribe to OnTick event or better use class derived from ContextObserver.
var yPositionTracker = new ContextTracker <string, double>
(
context,
c => c["freeFallEntity"].Y.Position
);
context.Tick(1);
//Context tracker implements IReadonlyDictionary.
Console.WriteLine($"\nOn tick 10345 y position is {yPositionTracker[10345]}");
Console.WriteLine($"\nOn time 1.27 y position is {yPositionTracker.GetApproximately(1.27)}");
//Throws exception because tracker has started recording when time is context
//was already 1.00.
//Console.WriteLine($"On time 0.4 y position is {yPositionTracker.GetApproximately(0.4)}");
//Throws exception because tracker hasn't record data yet because time in context is 2.00.
//Console.WriteLine($"On time 2.7 y position is {yPositionTracker.GetApproximately(2.7)}");
//Don't forget to dispose tracker when you don't need it anymore.
//It will increase performance because tracker doesn't record data anymore.
yPositionTracker.Dispose();
context.Tick(1);
//Time is context is 3.0, but tracker is already disposed and doesn't record data anymore.
Console.WriteLine
(
$"\nTracker records data during time span {yPositionTracker.ObservationBeginTime} - {yPositionTracker.LastObservationTime}" +
$"\nAverage y position is {yPositionTracker.Sum(record => record.Value) / yPositionTracker.Count}"
);
//However, if you want to record only max, min, average value etc,
//better use ContextDependentValue, because it doesn't use a lot of memory
//to record value in each tick.
var maxYVelocity = new ContextDependentValue <string, double>
(
startValue: context["freeFallEntity"].Y.Velocity,
observableContext: context,
newValueFunc: (c, oldValue) =>
c["freeFallEntity"].Velocity > oldValue ? new double?(c["freeFallEntity"].Velocity) : null
//null value means that there is no reason to change value
);
context.Tick(1);
Console.WriteLine
(
$"\nMax y velocity in time span {maxYVelocity.ObservationBeginTime} - " +
$"{maxYVelocity.LastObservationTime} is {maxYVelocity.Value}"
);
//So, lets create something more complex.
//What about the spring pendulum with air resistance?
var pendulumContext = new PhysicalContext <PendulumEntities>(dt, 2);
var axis = new PointMass(0, 0, 0, 0);
var mass = new PointMass(1, 0, 0, 0);
pendulumContext.AddEntity(PendulumEntities.Axis, axis);
pendulumContext.AddEntity
(
PendulumEntities.Mass,
mass,
c => new Force(0, c[PendulumEntities.Mass].Mass * freeFallAcceleration, 0), //Gravity
HookesLaw.GetLaw //Mechanix.Laws contains amount of static classes to help force evaluating.
(
PendulumEntities.Mass,
PendulumEntities.Axis,
1, //undeformed length of spring
10 //elasticity coefficient
)
);
//Or set of elastic balls.
var ballsContext = new PhysicalContext <int>(dt, 100);
var random = new Random();
const double radius = 1;
const double elasticity = 100;
for (int i = 0; i < 100; ++i)
{
var ball = new PointMass
(
new AxisStatus(random.NextDouble(), random.NextDouble()),
new AxisStatus(random.NextDouble(), random.NextDouble()),
new AxisStatus(random.NextDouble(), random.NextDouble()),
random.NextDouble()
);
ballsContext.AddEntity
(
i,
ball,
c =>
{
var force = Force.Zero;
foreach (var pair in c)
{
if (pair.Key != i)
{
force += RadialCollisionLaw.Eval
(
c[i],
pair.Value,
radius,
elasticity
);
}
}
return(force);
}
);
}
}
