public static bool RemoveChildFromCompound(CompoundCollidable compound, Func<CompoundChild, bool> removalPredicate, IList<ShapeDistributionInformation> childContributions,
out ShapeDistributionInformation distributionInfo, out float weight, out float removedWeight, out Vector3 removedCenter)
{
bool removalOccurred = false;
removedWeight = 0;
removedCenter = new Vector3();
for (int i = compound.children.Count - 1; i >= 0; i--)
{
//The shape doesn't change during this process. The entity could, though.
//All of the other collidable information, like the Tag, CollisionRules, Events, etc. all stay the same.
var child = compound.children.Elements[i];
if (removalPredicate(child))
{
removalOccurred = true;
var entry = child.Entry;
removedWeight += entry.Weight;
Vector3 toAdd;
Vector3.Multiply(ref entry.LocalTransform.Position, entry.Weight, out toAdd);
Vector3.Add(ref removedCenter, ref toAdd, out removedCenter);
//The child event handler must be unhooked from the compound.
child.CollisionInformation.events.Parent = null;
compound.children.FastRemoveAt(i);
}
}
if (!removalOccurred)
{
//No removal occurred, so we cannot proceed.
distributionInfo = new ShapeDistributionInformation();
weight = 0;
return false;
}
if (removedWeight > 0)
{
Vector3.Divide(ref removedCenter, removedWeight, out removedCenter);
}
//Compute the contributions from the original shape to the new form of the original collidable.
distributionInfo = new ShapeDistributionInformation();
weight = 0;
for (int i = compound.children.Count - 1; i >= 0; i--)
{
var child = compound.children.Elements[i];
var entry = child.Entry;
var contribution = childContributions[child.shapeIndex];
Vector3.Add(ref contribution.Center, ref entry.LocalTransform.Position, out contribution.Center);
Vector3.Multiply(ref contribution.Center, child.Entry.Weight, out contribution.Center);
Vector3.Add(ref contribution.Center, ref distributionInfo.Center, out distributionInfo.Center);
distributionInfo.Volume += contribution.Volume;
weight += entry.Weight;
}
//Average the center out.
Vector3.Divide(ref distributionInfo.Center, weight, out distributionInfo.Center);
//Note that the 'entry' is from the Shape, and so the translations are local to the shape's center.
//That is not technically the center of the new collidable- distributionInfo.Center is.
//Offset the child collidables by -distributionInfo.Center using their local offset.
Vector3 offset;
Vector3.Negate(ref distributionInfo.Center, out offset);
//Compute the unscaled inertia tensor.
for (int i = compound.children.Count - 1; i >= 0; i--)
{
var child = compound.children.Elements[i];
var entry = child.Entry;
Vector3 transformedOffset;
Quaternion conjugate;
Quaternion.Conjugate(ref entry.LocalTransform.Orientation, out conjugate);
Vector3.Transform(ref offset, ref conjugate, out transformedOffset);
child.CollisionInformation.localPosition = transformedOffset;
var contribution = childContributions[child.shapeIndex];
CompoundShape.TransformContribution(ref entry.LocalTransform, ref distributionInfo.Center, ref contribution.VolumeDistribution, entry.Weight, out contribution.VolumeDistribution);
//Vector3.Add(ref entry.LocalTransform.Position, ref offsetA, out entry.LocalTransform.Position);
Matrix3x3.Add(ref contribution.VolumeDistribution, ref distributionInfo.VolumeDistribution, out distributionInfo.VolumeDistribution);
}
//Normalize the volume distribution.
Matrix3x3.Multiply(ref distributionInfo.VolumeDistribution, 1 / weight, out distributionInfo.VolumeDistribution);
//Update the hierarchies of the compounds.
//TODO: Create a new method that does this quickly without garbage. Requires a new Reconstruct method which takes a pool which stores the appropriate node types.
compound.hierarchy.Tree.Reconstruct(compound.children);
return true;
}
