/// <summary>
/// Constructs a compound collidable containing only the specified subset of children.
/// </summary>
/// <param name="shape">Shape to base the compound collidable on.</param>
/// <param name="childIndices">Indices of child shapes from the CompoundShape to include in the compound collidable.</param>
/// <returns>Compound collidable containing only the specified subset of children.</returns>
public static CompoundCollidable CreatePartialCompoundCollidable(CompoundShape shape, IList <int> childIndices)
{
if (childIndices.Count == 0)
{
throw new ArgumentException("Cannot create a compound from zero shapes.");
}
CompoundCollidable compound = new CompoundCollidable();
Vector3 center = new Vector3();
float totalWeight = 0;
for (int i = 0; i < childIndices.Count; i++)
{
//Create and add the child object itself.
var entry = shape.shapes[childIndices[i]];
compound.children.Add(new CompoundChild(shape, entry.Shape.GetCollidableInstance(), childIndices[i]));
//Grab its entry to compute the center of mass of this subset.
Vector3 toAdd;
Vector3.Multiply(ref entry.LocalTransform.Position, entry.Weight, out toAdd);
Vector3.Add(ref center, ref toAdd, out center);
totalWeight += entry.Weight;
}
if (totalWeight <= 0)
{
throw new ArgumentException("Compound has zero total weight; invalid configuration.");
}
Vector3.Divide(ref center, totalWeight, out center);
//Our subset of the compound is not necessarily aligned with the shape's origin.
//By default, an object will rotate around the center of the collision shape.
//We can't modify the shape data itself since it could be shared, which leaves
//modifying the local position of the collidable.
//We have the subset position in shape space, so pull the collidable back into alignment
//with the origin.
//This approach matches the rest of the CompoundHelper's treatment of subsets.
compound.LocalPosition = -center;
//Recompute the hierarchy for the compound.
compound.hierarchy.Tree.Reconstruct(compound.children);
compound.Shape = shape;
return(compound);
}
/// <summary>
/// Splits a single compound collidable into two separate compound collidables and computes information needed by the simulation.
/// </summary>
/// <param name="splitPredicate">Delegate which determines if a child in the original compound should be moved to the new compound.</param>
/// <param name="a">Original compound to be split. Children in this compound will be removed and added to the other compound.</param>
/// <param name="b">Compound to receive children removed from the original compound.</param>
/// <param name="distributionInfoA">Volume, volume distribution, and center information about the new form of the original compound collidable.</param>
/// <param name="distributionInfoB">Volume, volume distribution, and center information about the new compound collidable.</param>
/// <returns>Whether or not the predicate returned true for any element in the original compound and split the compound.</returns>
public static bool SplitCompound(Func <CompoundChild, bool> splitPredicate,
Entity <CompoundCollidable> a, out Entity <CompoundCollidable> b,
out ShapeDistributionInformation distributionInfoA, out ShapeDistributionInformation distributionInfoB)
{
var bCollidable = new CompoundCollidable {
Shape = a.CollisionInformation.Shape
};
b = null;
float weightA, weightB;
if (SplitCompound(splitPredicate, a.CollisionInformation, bCollidable, out distributionInfoA, out distributionInfoB, out weightA, out weightB))
{
//Reconfigure the entities using the data computed in the split.
float originalMass = a.mass;
if (a.CollisionInformation.children.Count > 0)
{
float newMassA = (weightA / (weightA + weightB)) * originalMass;
Matrix3x3.Multiply(ref distributionInfoA.VolumeDistribution, newMassA * InertiaHelper.InertiaTensorScale, out distributionInfoA.VolumeDistribution);
a.Initialize(a.CollisionInformation, newMassA, distributionInfoA.VolumeDistribution);
}
if (bCollidable.children.Count > 0)
{
float newMassB = (weightB / (weightA + weightB)) * originalMass;
Matrix3x3.Multiply(ref distributionInfoB.VolumeDistribution, newMassB * InertiaHelper.InertiaTensorScale, out distributionInfoB.VolumeDistribution);
b = new Entity <CompoundCollidable>();
b.Initialize(bCollidable, newMassB, distributionInfoB.VolumeDistribution);
}
SplitReposition(a, b, ref distributionInfoA, ref distributionInfoB, weightA, weightB);
return(true);
}
return(false);
}
/// <summary>
/// Removes a child from a compound collidable.
/// </summary>
/// <param name="compound">Compound collidable to remove a child from.</param>
/// <param name="removalPredicate">Callback which analyzes a child and determines if it should be removed from the compound.</param>
/// <param name="childContributions">Distribution contributions from all shapes in the compound shape. This can include shapes which are not represented in the compound.</param>
/// <param name="distributionInfo">Distribution information of the new compound.</param>
/// <param name="weight">Total weight of the new compound.</param>
/// <param name="removedWeight">Weight removed from the compound.</param>
/// <param name="removedCenter">Center of the chunk removed from the compound.</param>
/// <returns>Whether or not any removal took place.</returns>
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);
Quaternion.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);
}
/// <summary>
/// Splits a single compound collidable into two separate compound collidables and computes information needed by the simulation.
/// </summary>
/// <param name="splitPredicate">Delegate which determines if a child in the original compound should be moved to the new compound.</param>
/// <param name="a">Original compound to be split. Children in this compound will be removed and added to the other compound.</param>
/// <param name="b">Compound to receive children removed from the original compound.</param>
/// <param name="distributionInfoA">Volume, volume distribution, and center information about the new form of the original compound collidable.</param>
/// <param name="distributionInfoB">Volume, volume distribution, and center information about the new compound collidable.</param>
/// <param name="weightA">Total weight associated with the new form of the original compound collidable.</param>
/// <param name="weightB">Total weight associated with the new compound collidable.</param>
/// <returns>Whether or not the predicate returned true for any element in the original compound and split the compound.</returns>
public static bool SplitCompound(Func <CompoundChild, bool> splitPredicate,
CompoundCollidable a, CompoundCollidable b,
out ShapeDistributionInformation distributionInfoA, out ShapeDistributionInformation distributionInfoB,
out float weightA, out float weightB)
{
bool splitOccurred = false;
for (int i = a.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 = a.children.Elements[i];
if (splitPredicate(child))
{
splitOccurred = true;
a.children.FastRemoveAt(i);
b.children.Add(child);
//The child event handler must be unhooked from the old compound and given to the new one.
child.CollisionInformation.events.Parent = b.Events;
}
}
if (!splitOccurred)
{
//No split occurred, so we cannot proceed.
distributionInfoA = new ShapeDistributionInformation();
distributionInfoB = new ShapeDistributionInformation();
weightA = 0;
weightB = 0;
return(false);
}
//Compute the contributions from the original shape to the new form of the original collidable.
distributionInfoA = new ShapeDistributionInformation();
weightA = 0;
distributionInfoB = new ShapeDistributionInformation();
weightB = 0;
for (int i = a.children.Count - 1; i >= 0; i--)
{
var child = a.children.Elements[i];
var entry = child.Entry;
Vector3 weightedCenter;
Vector3.Multiply(ref entry.LocalTransform.Position, entry.Weight, out weightedCenter);
Vector3.Add(ref weightedCenter, ref distributionInfoA.Center, out distributionInfoA.Center);
distributionInfoA.Volume += entry.Shape.Volume;
weightA += entry.Weight;
}
for (int i = b.children.Count - 1; i >= 0; i--)
{
var child = b.children.Elements[i];
var entry = child.Entry;
Vector3 weightedCenter;
Vector3.Multiply(ref entry.LocalTransform.Position, entry.Weight, out weightedCenter);
Vector3.Add(ref weightedCenter, ref distributionInfoB.Center, out distributionInfoB.Center);
distributionInfoB.Volume += entry.Shape.Volume;
weightB += entry.Weight;
}
//Average the center out.
if (weightA > 0)
{
Vector3.Divide(ref distributionInfoA.Center, weightA, out distributionInfoA.Center);
}
if (weightB > 0)
{
Vector3.Divide(ref distributionInfoB.Center, weightB, out distributionInfoB.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- distributionInfoA.Center is.
//Offset the child collidables by -distributionInfoA.Center using their local offset.
Vector3 offsetA;
Vector3.Negate(ref distributionInfoA.Center, out offsetA);
Vector3 offsetB;
Vector3.Negate(ref distributionInfoB.Center, out offsetB);
//Compute the unscaled inertia tensor.
for (int i = a.children.Count - 1; i >= 0; i--)
{
var child = a.children.Elements[i];
var entry = child.Entry;
Vector3 transformedOffset;
Quaternion conjugate;
Quaternion.Conjugate(ref entry.LocalTransform.Orientation, out conjugate);
Quaternion.Transform(ref offsetA, ref conjugate, out transformedOffset);
child.CollisionInformation.localPosition = transformedOffset;
Matrix3x3 contribution;
CompoundShape.TransformContribution(ref entry.LocalTransform, ref distributionInfoA.Center, ref entry.Shape.volumeDistribution, entry.Weight, out contribution);
Matrix3x3.Add(ref contribution, ref distributionInfoA.VolumeDistribution, out distributionInfoA.VolumeDistribution);
}
for (int i = b.children.Count - 1; i >= 0; i--)
{
var child = b.children.Elements[i];
var entry = child.Entry;
Vector3 transformedOffset;
Quaternion conjugate;
Quaternion.Conjugate(ref entry.LocalTransform.Orientation, out conjugate);
Quaternion.Transform(ref offsetB, ref conjugate, out transformedOffset);
child.CollisionInformation.localPosition = transformedOffset;
Matrix3x3 contribution;
CompoundShape.TransformContribution(ref entry.LocalTransform, ref distributionInfoB.Center, ref entry.Shape.volumeDistribution, entry.Weight, out contribution);
Matrix3x3.Add(ref contribution, ref distributionInfoB.VolumeDistribution, out distributionInfoB.VolumeDistribution);
}
//Normalize the volume distribution.
Matrix3x3.Multiply(ref distributionInfoA.VolumeDistribution, 1 / weightA, out distributionInfoA.VolumeDistribution);
Matrix3x3.Multiply(ref distributionInfoB.VolumeDistribution, 1 / weightB, out distributionInfoB.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.
a.hierarchy.Tree.Reconstruct(a.children);
b.hierarchy.Tree.Reconstruct(b.children);
return(true);
}