public static List <Vector2> ElectricFieldLineFast(IEnumerable <PhysicalObject> system, Vector2 initPos, Func <float, Vector2, bool> endFunc, bool startFromNegative, float delta = 1e-3f)
{
Vector2 f(float t, Vector2 v)
{
var e = PSystem.GetElectricFieldAt(system, v);
return(e / e.Length() * 100f);
}
var result = new List <Vector2>();
float num1 = 0f;
result.Add(initPos);
while (!endFunc(num1, result.Last()) || Single.IsNaN(result.Last().X))
{
var vec = f(num1, initPos);
result.Add(initPos + delta * vec);
if (TryFindMatch(
system,
(p) => p.Charge != 0 && DistFromPointToSegment(result[result.Count - 2], result.Last(), p.Position) < 0.1f,
out PhysicalObject obj))
{
result.RemoveAt(result.Count - 1);
result.Add(obj.Position);
break;
}
num1 += delta;
initPos = result.Last();
}
return(result);
}
/// <summary>
/// Calculate the electric field line
/// </summary>
/// <param name="system">List of physical objects in the system</param>
/// <param name="initPos">Starting position of the electric field line</param>
/// <param name="endFunc">stop calculating the line if true</param>
/// <param name="startFromNegative">whether or not starting from negative charged object</param>
/// <param name="delta">small step of calculation, the smaller, the better</param>
/// <returns>the list of points that represent the electric field line</returns>
public static List <Vector2> ElectricFieldLine(IEnumerable <PhysicalObject> system, Vector2 initPos, Func <float, Vector2, bool> endFunc, bool startFromNegative, float delta = 1e-3f)
{
Func <Vector2, Vector2> electric_field = PSystem.GetElectricFieldFunc(system);
Vector2 f(float t, Vector2 v)
{
// get electriv field at v
var e = electric_field(v);
// fix the length with 100
return(e / e.Length() * 100f);
}
List <Vector2> vectorArrays = new List <Vector2>();
float num1 = 0f;
vectorArrays.Add(initPos);
while (!endFunc(num1, vectorArrays.Last()))
{
Vector2 nums = f(num1, initPos);
Vector2 nums1 = f(num1, initPos + (nums * delta));
vectorArrays.Add(initPos + (delta * 0.5f * (nums + nums1)));
// if the line reached an charge very closely
if (TryFindMatch(
system,
(p) => p.Charge != 0 && DistFromPointToSegment(vectorArrays[vectorArrays.Count - 2], vectorArrays.Last(), p.Position) < 0.1f,
out PhysicalObject obj))
{
// remove the last element
vectorArrays.RemoveAt(vectorArrays.Count - 1);
// add the position of the object that this line is approaching
vectorArrays.Add(obj.Position);
// break this loop
break;
}
num1 += delta;
initPos = vectorArrays.Last();
}
return(vectorArrays);
}
