private void OnFrameCallback(object sender, EventArgs e)
{
if (_timeTracker != null)
{
_timeTracker.Update();
InvalidateVisual();
}
}
private void UpdateChildren(object sender, EventArgs e)
{
//update time delta
_timeTracker.Update();
foreach (UIElement child in LogicalTreeHelper.GetChildren(this))
{
Vector velocity;
if (_childrenVelocities.ContainsKey(child))
{
//get the velocity that we previously stored
velocity = _childrenVelocities[child];
}
else
{
//setup the initial velocity randomly
velocity = new Vector(0, 0);
}
//compute velocity dampening
velocity = velocity * _drag;
Point truePosition = GetTruePosition(child);
Rect childRect = new Rect(truePosition, child.RenderSize);
//accumulate forces
Vector forces = new Vector(0, 0);
//add wall repulsion
forces.X += _borderforce / Math.Max(1, childRect.Left);
forces.X -= _borderforce / Math.Max(1, this.RenderSize.Width - childRect.Right);
forces.Y += _borderforce / Math.Max(1, childRect.Top);
forces.Y -= _borderforce / Math.Max(1, this.RenderSize.Height - childRect.Bottom);
//each other child pushes away based on the square distance
foreach (UIElement otherchild in LogicalTreeHelper.GetChildren(this))
{
//dont push against itself
if (otherchild == child)
{
continue;
}
Point otherchildtruePosition = GetTruePosition(otherchild);
Rect otherchildRect = new Rect(otherchildtruePosition, otherchild.RenderSize);
//make sure rects aren't the same
if (otherchildRect == childRect)
{
continue;
}
//ignore children with a size of 0,0
if (otherchildRect.Width == 0 && otherchildRect.Height == 0 || childRect.Width == 0 && childRect.Height == 0)
{
continue;
}
//vector from current other child to current child
Vector toChild;
double length;
//are they overlapping? if so, distance is 0
if (AreRectsOverlapping(childRect, otherchildRect))
{
toChild = new Vector(0, 0);
}
else
{
toChild = VectorBetweenRects(childRect, otherchildRect);
}
length = toChild.Length;
if (length < 1)
{
length = 1;
Point childCenter = GetCenter(childRect);
Point otherchildCenter = GetCenter(otherchildRect);
//compute toChild from the center of both rects
toChild = childCenter - otherchildCenter;
}
double childpush = _childforce / length;
toChild.Normalize();
forces += toChild * childpush;
}
//add forces to velocity and store it for next iteration
velocity += forces;
_childrenVelocities[child] = velocity;
//move the object based on it's velocity
SetTruePosition(child, truePosition + _timeTracker.DeltaSeconds * velocity);
}
}
protected void OnFrameCallback(object sender, EventArgs e)
{
UpdateParticles(_timeTracker.Update());
}
