/// <summary>
/// Precomputes the transform to bring triangles from their native local space to the local space of the convex.
/// </summary>
/// <param name="convexInverseWorldTransform">Inverse of the world transform of the convex shape.</param>
/// <param name="fromMeshLocalToConvexLocal">Transform to apply to native local triangles to bring them into the local space of the convex.</param>
protected override void PrecomputeTriangleTransform(ref AffineTransform convexInverseWorldTransform, out AffineTransform fromMeshLocalToConvexLocal)
{
//MobileMeshes only have TransformableMeshData sources.
var data = ((TransformableMeshData)mesh.Shape.TriangleMesh.Data);
//The mobile mesh has a shape-based transform followed by the rigid body transform.
AffineTransform mobileMeshWorldTransform;
AffineTransform.CreateFromRigidTransform(ref mesh.worldTransform, out mobileMeshWorldTransform);
AffineTransform combinedMobileMeshWorldTransform;
AffineTransform.Multiply(ref data.worldTransform, ref mobileMeshWorldTransform, out combinedMobileMeshWorldTransform);
AffineTransform.Multiply(ref combinedMobileMeshWorldTransform, ref convexInverseWorldTransform, out fromMeshLocalToConvexLocal);
}
///<summary>
/// Updates the manifold.
///</summary>
///<param name="dt">Timestep duration.</param>
public override void Update(float dt)
{
//First, refresh all existing contacts. This is an incremental manifold.
var transform = MeshTransform;
ContactRefresher.ContactRefresh(contacts, supplementData, ref convex.worldTransform, ref transform, contactIndicesToRemove);
RemoveQueuedContacts();
CleanUpOverlappingTriangles();
//Get all the overlapped triangle indices.
//Note that the collection of triangles is left up to the child implementation.
//We're basically treating the child class like an indexable collection.
//A little gross to have it organized this way instead of an explicit collection to separate the logic up. Would be nice to improve someday!
int triangleCount = FindOverlappingTriangles(dt);
//Just use 32 elements for all the lists and sets in this system.
const int bufferPoolSizePower = 5;
BoundarySets boundarySets;
if (UseImprovedBoundaryHandling)
{
boundarySets = new BoundarySets(bufferPoolSizePower);
}
else
{
boundarySets = new BoundarySets();
}
var candidatesToAdd = new QuickList <ContactData>(BufferPools <ContactData> .Thread, bufferPoolSizePower);
//A single triangle shape will be reused for all operations. It's pulled from a thread local pool to avoid holding a TriangleShape around for every single contact manifold or pair tester.
var localTriangleShape = PhysicsThreadResources.GetTriangle();
//Precompute the transform to take triangles from their native local space to the convex's local space.
RigidTransform inverseConvexWorldTransform;
RigidTransform.Invert(ref convex.worldTransform, out inverseConvexWorldTransform);
AffineTransform convexInverseWorldTransform;
AffineTransform.CreateFromRigidTransform(ref inverseConvexWorldTransform, out convexInverseWorldTransform);
AffineTransform fromMeshLocalToConvexLocal;
PrecomputeTriangleTransform(ref convexInverseWorldTransform, out fromMeshLocalToConvexLocal);
//Grab the convex's local space bounding box up front. This will be used for a secondary pruning step.
BoundingBox convexLocalBoundingBox;
convex.Shape.GetBoundingBox(ref Toolbox.RigidIdentity, out convexLocalBoundingBox);
Matrix3x3 orientation;
Matrix3x3.CreateFromQuaternion(ref convex.worldTransform.Orientation, out orientation);
var guaranteedContacts = 0;
for (int i = 0; i < triangleCount; i++)
{
//Initialize the local triangle.
TriangleIndices indices;
if (ConfigureLocalTriangle(i, localTriangleShape, out indices))
{
//Put the triangle into the local space of the convex.
AffineTransform.Transform(ref localTriangleShape.vA, ref fromMeshLocalToConvexLocal, out localTriangleShape.vA);
AffineTransform.Transform(ref localTriangleShape.vB, ref fromMeshLocalToConvexLocal, out localTriangleShape.vB);
AffineTransform.Transform(ref localTriangleShape.vC, ref fromMeshLocalToConvexLocal, out localTriangleShape.vC);
//Do one last AABB test between the convex and triangle in the convex's local space.
//This can prune out a lot of triangles when dealing with larger objects, and it's pretty cheap to do.
BoundingBox triangleBoundingBox;
Toolbox.GetTriangleBoundingBox(ref localTriangleShape.vA, ref localTriangleShape.vB, ref localTriangleShape.vC, out triangleBoundingBox);
bool intersecting;
triangleBoundingBox.Intersects(ref convexLocalBoundingBox, out intersecting);
if (!intersecting)
{
continue;
}
//Find a pairtester for the triangle.
TrianglePairTester pairTester;
if (!activePairTesters.TryGetValue(indices, out pairTester))
{
pairTester = GetTester();
pairTester.Initialize(convex.Shape);
activePairTesters.Add(indices, pairTester);
}
pairTester.Updated = true;
//Now, generate a contact between the two shapes.
TinyStructList <ContactData> contactList;
if (pairTester.GenerateContactCandidates(localTriangleShape, out contactList))
{
for (int j = 0; j < contactList.Count; j++)
{
ContactData contact;
contactList.Get(j, out contact);
if (UseImprovedBoundaryHandling)
{
if (AnalyzeCandidate(ref indices, localTriangleShape, pairTester, ref contact, ref boundarySets))
{
//This is let through if there's a face contact. Face contacts cannot be blocked.
guaranteedContacts++;
AddLocalContact(ref contact, ref orientation, ref candidatesToAdd);
}
}
else
{
AddLocalContact(ref contact, ref orientation, ref candidatesToAdd);
}
}
}
//Get the voronoi region from the contact candidate generation. Possibly just recalculate, since most of the systems don't calculate it.
//Depending on which voronoi region it is in (Switch on enumeration), identify the indices composing that region. For face contacts, don't bother- just add it if unique.
//For AB, AC, or BC, add an Edge to the blockedEdgeRegions set with the corresponding indices.
//For A, B, or C, add the index of the vertex to the blockedVertexRegions set.
//If the edge/vertex is already present in the set, then DO NOT add the contact.
//When adding a contact, add ALL other voronoi regions to the blocked sets.
}
}
if (UseImprovedBoundaryHandling)
{
//If there were no face contacts that absolutely must be included, we may get into a very rare situation
//where absolutely no contacts get created. For example, a sphere falling directly on top of a vertex in a flat terrain.
//It will generally get locked out of usage by belonging only to restricted regions (numerical issues make it visible by both edges and vertices).
//In some cases, the contacts will be ignored instead of corrected (e.g. spheres).
//To prevent objects from just falling through the ground in such a situation, force-correct the contacts regardless of the pair tester's desires.
//Sure, it might not be necessary under normal circumstances, but it's a better option than having no contacts.
//TODO: There is another option: Changing restricted regions so that a vertex only restricts the other two vertices and the far edge,
//and an edge only restricts the far vertex and other two edges. This introduces an occasional bump though...
//It's possible, in very specific instances, for an object to wedge itself between two adjacent triangles.
//For this state to continue beyond a brief instant generally requires the object be orientation locked and slender.
//However, some characters fit this description, so it can't be ignored!
//Conceptually, this issue can occur at either a vertex junction or a shared edge (usually on extremely flat surfaces only).
//However, an object stuck between multiple triangles is not in a stable state. In the edge case, the object gets shoved to one side
//as one contact 'wins' the solver war. That's not enough to escape, unfortunately.
//The vertex case, on the other hand, is degenerate and decays into an edge case rapidly thanks to this lack of stability.
//So, we don't have to explicitly handle the somewhat more annoying and computationally expensive vertex unstucking case, because the edge case handles both! :)
//This isn't a completely free operation, but it's guarded behind pretty rare conditions.
//Essentially, we will check to see if there's just edge contacts fighting against each other.
//If they are, then we will correct any stuck-contributing normals to the triangle normal.
if (boundarySets.VertexContacts.Count == 0 && guaranteedContacts == 0 && boundarySets.EdgeContacts.Count > 1)
{
//There are only edge contacts, check to see if:
//all normals are coplanar, and
//at least one normal faces against the other normals (meaning it's probably stuck, as opposed to just colliding on a corner).
bool allNormalsInSamePlane = true;
bool atLeastOneNormalAgainst = false;
var firstNormal = boundarySets.EdgeContacts.Elements[0].ContactData.Normal;
boundarySets.EdgeContacts.Elements[0].CorrectedNormal.Normalize();
float dot;
Vector3.Dot(ref firstNormal, ref boundarySets.EdgeContacts.Elements[0].CorrectedNormal, out dot);
if (Math.Abs(dot) > .01f)
{
//Go ahead and test the first contact separately, since we're using its contact normal to determine coplanarity.
allNormalsInSamePlane = false;
}
else
{
//TODO: Note that we're only checking the new edge contacts, not the existing contacts.
//It's possible that some existing contacts could interfere and cause issues, but for the sake of simplicity and due to rarity
//we'll ignore that possibility for now.
for (int i = 1; i < boundarySets.EdgeContacts.Count; i++)
{
Vector3.Dot(ref boundarySets.EdgeContacts.Elements[i].ContactData.Normal, ref firstNormal, out dot);
if (dot < 0)
{
atLeastOneNormalAgainst = true;
}
//Check to see if the normal is outside the plane.
Vector3.Dot(ref boundarySets.EdgeContacts.Elements[i].ContactData.Normal, ref boundarySets.EdgeContacts.Elements[0].CorrectedNormal, out dot);
if (Math.Abs(dot) > .01f)
{
//We are not stuck!
allNormalsInSamePlane = false;
break;
}
}
}
if (allNormalsInSamePlane && atLeastOneNormalAgainst)
{
//Uh oh! all the normals are parallel... The object is probably in a weird situation.
//Let's correct the normals!
//Already normalized the first contact above.
//We don't need to perform the perpendicularity test here- we did that before! We know it's perpendicular already.
boundarySets.EdgeContacts.Elements[0].ContactData.Normal = boundarySets.EdgeContacts.Elements[0].CorrectedNormal;
boundarySets.EdgeContacts.Elements[0].ShouldCorrect = true;
for (int i = 1; i < boundarySets.EdgeContacts.Count; i++)
{
//Must normalize the corrected normal before using it.
boundarySets.EdgeContacts.Elements[i].CorrectedNormal.Normalize();
Vector3.Dot(ref boundarySets.EdgeContacts.Elements[i].CorrectedNormal, ref boundarySets.EdgeContacts.Elements[i].ContactData.Normal, out dot);
if (dot < .01)
{
//Only bother doing the correction if the normal appears to be pointing nearly horizontally- implying that it's a contributor to the stuckness!
//If it's blocked, the next section will use the corrected normal- if it's not blocked, the next section will use the direct normal.
//Make them the same thing :)
boundarySets.EdgeContacts.Elements[i].ContactData.Normal = boundarySets.EdgeContacts.Elements[i].CorrectedNormal;
boundarySets.EdgeContacts.Elements[i].ShouldCorrect = true;
//Note that the penetration depth is NOT corrected. The contact's depth no longer represents the true depth.
//However, we only need to have some penetration depth to get the object to escape the rut.
//Furthermore, the depth computed from the horizontal opposing contacts is known to be less than the depth in the perpendicular direction.
//If the current depth was NOT less than the true depth along the corrected normal, then the collision detection system
//would have picked a different depth, as it finds a reasonable approximation of the minimum penetration!
//As a consequence, this contact will not be active beyond the object's destuckification, because its contact depth will be negative (or very close to it).
}
}
}
}
for (int i = 0; i < boundarySets.EdgeContacts.Count; i++)
{
//Only correct if it's allowed AND it's blocked.
//If it's not blocked, the contact being created is necessary!
//The normal generated by the triangle-convex tester is already known not to
//violate the triangle sidedness.
if (!boundarySets.BlockedEdgeRegions.Contains(boundarySets.EdgeContacts.Elements[i].Edge))
{
//If it's not blocked, use the contact as-is without correcting it.
AddLocalContact(ref boundarySets.EdgeContacts.Elements[i].ContactData, ref orientation, ref candidatesToAdd);
}
else if (boundarySets.EdgeContacts.Elements[i].ShouldCorrect || guaranteedContacts == 0)
{
//If it is blocked, we can still make use of the contact. But first, we need to change the contact normal to ensure that
//it will not interfere (and cause a bump or something).
float dot;
boundarySets.EdgeContacts.Elements[i].CorrectedNormal.Normalize();
Vector3.Dot(ref boundarySets.EdgeContacts.Elements[i].CorrectedNormal, ref boundarySets.EdgeContacts.Elements[i].ContactData.Normal, out dot);
boundarySets.EdgeContacts.Elements[i].ContactData.Normal = boundarySets.EdgeContacts.Elements[i].CorrectedNormal;
boundarySets.EdgeContacts.Elements[i].ContactData.PenetrationDepth *= MathHelper.Max(0, dot); //Never cause a negative penetration depth.
AddLocalContact(ref boundarySets.EdgeContacts.Elements[i].ContactData, ref orientation, ref candidatesToAdd);
}
//If it's blocked AND it doesn't allow correction, ignore its existence.
}
for (int i = 0; i < boundarySets.VertexContacts.Count; i++)
{
if (!boundarySets.BlockedVertexRegions.Contains(boundarySets.VertexContacts.Elements[i].Vertex))
{
//If it's not blocked, use the contact as-is without correcting it.
AddLocalContact(ref boundarySets.VertexContacts.Elements[i].ContactData, ref orientation, ref candidatesToAdd);
}
else if (boundarySets.VertexContacts.Elements[i].ShouldCorrect || guaranteedContacts == 0)
{
//If it is blocked, we can still make use of the contact. But first, we need to change the contact normal to ensure that
//it will not interfere (and cause a bump or something).
float dot;
boundarySets.VertexContacts.Elements[i].CorrectedNormal.Normalize();
Vector3.Dot(ref boundarySets.VertexContacts.Elements[i].CorrectedNormal, ref boundarySets.VertexContacts.Elements[i].ContactData.Normal, out dot);
boundarySets.VertexContacts.Elements[i].ContactData.Normal = boundarySets.VertexContacts.Elements[i].CorrectedNormal;
boundarySets.VertexContacts.Elements[i].ContactData.PenetrationDepth *= MathHelper.Max(0, dot); //Never cause a negative penetration depth.
AddLocalContact(ref boundarySets.VertexContacts.Elements[i].ContactData, ref orientation, ref candidatesToAdd);
}
//If it's blocked AND it doesn't allow correction, ignore its existence.
}
boundarySets.Dispose();
}
//Remove stale pair testers.
for (int i = activePairTesters.Count - 1; i >= 0; --i)
{
var tester = activePairTesters.Values[i];
if (!tester.Updated)
{
tester.CleanUp();
GiveBackTester(tester);
activePairTesters.FastRemove(activePairTesters.Keys[i]);
}
else
{
tester.Updated = false;
}
}
//Some child types will want to do some extra post processing on the manifold.
ProcessCandidates(ref candidatesToAdd);
//Check if adding the new contacts would overflow the manifold.
if (contacts.Count + candidatesToAdd.Count > 4)
{
//Adding all the contacts would overflow the manifold. Reduce to the best subset.
var reducedCandidates = new QuickList <ContactData>(BufferPools <ContactData> .Thread, bufferPoolSizePower);
ContactReducer.ReduceContacts(contacts, ref candidatesToAdd, contactIndicesToRemove, ref reducedCandidates);
RemoveQueuedContacts();
for (int i = reducedCandidates.Count - 1; i >= 0; i--)
{
Add(ref reducedCandidates.Elements[i]);
reducedCandidates.RemoveAt(i);
}
reducedCandidates.Dispose();
}
else if (candidatesToAdd.Count > 0)
{
//Won't overflow the manifold, so just toss it in PROVIDED that it isn't too close to something else.
for (int i = 0; i < candidatesToAdd.Count; i++)
{
Add(ref candidatesToAdd.Elements[i]);
}
}
PhysicsThreadResources.GiveBack(localTriangleShape);
candidatesToAdd.Dispose();
}