private void Subdivide()
{
_subRegions = new BHRegion[8];
var midpoint = (Max + Min) / 2f;
float3 dimension = (Max - Min) / 2f;
float3 rightShift = new float3(dimension.x, 0f, 0f);
float3 upShift = new float3(0f, dimension.y, 0f);
float3 forwardShift = new float3(0f, 0f, dimension.z);
_subRegions[0] = new BHRegion(midpoint, Max);
_subRegions[1] = new BHRegion(midpoint - rightShift, Max - rightShift);
_subRegions[2] = new BHRegion(midpoint - rightShift - forwardShift, Max - rightShift - forwardShift);
_subRegions[3] = new BHRegion(midpoint - forwardShift, Max - forwardShift);
_subRegions[4] = new BHRegion(midpoint - upShift, Max - upShift);
_subRegions[5] = new BHRegion(midpoint - upShift - rightShift, Max - upShift - rightShift);
_subRegions[6] = new BHRegion(midpoint - upShift - rightShift - forwardShift, Max - upShift - rightShift - forwardShift);
_subRegions[7] = new BHRegion(midpoint - upShift - forwardShift, Max - upShift - forwardShift);
}
private void ForceWalkTraversal(BHRegion region, Entity entity, float mass, float3 position, ref float3 resultant)
{
if (region == null || region.IsEmpty)
{
return;
}
BHRegion currentRegion = region;
if (currentRegion.IsExternal)
{
if (currentRegion.CurrentRegionEntity.Value.entity != entity)
{
// TODO: Add gravitational stuff.
var diff = currentRegion.CurrentRegionEntity.Value.position - position;
var magnitude = GRAVITATIONAL_CONSTANT * (currentRegion.CurrentRegionEntity.Value.mass * mass) / math.pow(math.pow(diff.x, 2) + math.pow(diff.y, 2) + math.pow(diff.z, 2), 1.5f);
resultant += magnitude * math.normalize(diff);
}
}
else
{
var s = currentRegion.Dimension;
var d = math.length(position - currentRegion.CenterOfMass);
if (s / d < THETA)
{
// TODO: Add gravitational stuff; use currentRegion.TotalMass here.
var diff = currentRegion.CenterOfMass - position;
var magnitude = GRAVITATIONAL_CONSTANT * (currentRegion.TotalMass * mass) / math.pow(math.pow(diff.x, 2) + math.pow(diff.y, 2) + math.pow(diff.z, 2), 1.5f);
resultant += magnitude * math.normalize(diff);
}
else
{
for (int i = 0; i < 8; i++)
{
ForceWalkTraversal(region.Subregions[i], entity, mass, position, ref resultant);
}
}
}
}
public void PreOrderTraverseTree(Action <BHRegion> action, BHRegion startRegion)
{
if (startRegion == null)
{
return;
}
BHRegion currentRegion = startRegion;
action(currentRegion);
if (currentRegion.IsExternal)
{
return;
}
else if (currentRegion.IsInternal)
{
for (int i = 0; i < 8; i++)
{
PreOrderTraverseTree(action, currentRegion.Subregions[i]);
}
}
}
public BarnesHutTree(float3 min, float3 max)
{
_root = new BHRegion(min, max);
}