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  3. FCollisionConstraintAllocator

FCollisionConstraintAllocator

An allocator and container of collision constraints that supports reuse of constraints from the previous tick.

Unreal Engine C++ API Reference > Runtime > Chaos > Chaos > Collision

References

   
Module Chaos
Header /Engine/Source/Runtime/Experimental/Chaos/Public/Chaos/Collision/CollisionConstraintAllocator.h
Include #include "Chaos/Collision/CollisionConstraintAllocator.h"

Syntax

class FCollisionConstraintAllocator

Remarks

All constraint pointers are persistent in memory until Destroy() is called, or until they are pruned.

This allocator maintains the set of all overlapping particle pairs, with each overlapping particle pair managed by a FParticlePairMidPhase object. the MidPhase object is what actually calls the Narrow Phase and maintains the set of collision constraints for all the shape pairs on the particles.

Constraints are allocated during the collision detection phase and retained between ticks. An attempt to create a constraint for the same shape pair as seen on the previous tick will return the existing collision constraint with all of its data intact.

The allocator also keeps a list of Standard and Swept collision constraints that are active for the current tick. This list gets reset and rebuilt every frame during collision detection. It may get added to by the IslandManager if some islands are woken following collision detection.

The allocators Epoch counter is used to determine whether a constraint (or midphase object) generated any contacts for the current frame. When a midphase creates or updates a constraint, it copies the current Epoch counter.

The Midphase list is pruned at the end of each tick so if particles are destroyed or a particle pair is no longer overlapping, the collisions will be destroyed.

When particles are destroyed, we do not immediately destroy the MidPhases (or Collisions) that are associoated with the particle. Instead, we clear the particle pointer from them, but leave their destruction to the pruning process. This avoids the need to parse collision and midphase lists whenever a particle is disabled.

NOTE: To reduce RBAN memory use, we do not create any collision blocks until the first call to CreateCollisionConstraint (see ConstraintPool initialization)

Constructors

  Type Name Description
Public function    
Public function    
Public function  

FCollisionConstraintAllocator ( const int32 InNumCollisionsPerBlock
)

  

Destructors

  Type Name Description
Public function    

Functions

  Type Name Description
Public function void

AddResimConstraints ( const TArray< FPBDCollisionConstraint >& InConstraints,
const FCollisionContext Context
)

 Add a set of pre-built constraints and build required internal mapping data This is used by the resim cache when restoring constraints after a desync.
Public function void Called at the start of the tick to prepare for collision detection. Resets the list of active contacts.
Public function void Called at the start of the frame to clear the frame's active collision list.
Public function void Called after collision detection to clean up Prunes unused contacts.
Public function Const TArrayView< FPBDCollisionConstraint *const > The set of sweep collision constraints for the current tick (created or reinstated)
Public function Const TArrayView< const FPBDCollisionConstraint *const > The set of collision constraints for the current tick (created or reinstated)
Public function Const TArrayView< FPBDCollisionConstraint *const > The set of collision constraints for the current tick (created or reinstated)
Public function FCollisionContextAllocator *

GetContextAllocator ( const int32 Index
)

  
Public function Const int32  
Public function bool Has the constraint expired.
Public function void If we add new constraints after collision detection, do what needs to be done to add them to the system.
Public function void Collect all the midphases created on the context allocators (probably on multiple threads) and register them
Public function void Called each tick after the graph is updated to remove unused collisions.
Public function void Destroy all collision and caches involving the particle Called when a particle is destroyed or disabled (not sleeping).
Public function void

Reset ()

 Destroy all constraints.
Public function void  
Public function void

SetMaxContexts ( const int32 MaxContexts
)

  
Public function void Sort all the constraints for better solver stability.
Public function Const void

VisitCollisions ( const TLambda& Visitor
)

 Iterate over all collisions (write-enabled), including sleeping ones Visitor signature: ECollisionVisitorResult(FPBDCollisionConstraint&)
Public function Const void

VisitConstCollisions ( const TLambda& Visitor
)

 Iterate over all collisions (read-only), including sleeping ones Visitor signature: ECollisionVisitorResult(const FPBDCollisionConstraint&)
Public function void

VisitMidPhases ( const TLambda& Visitor
)

 Iterate over all midphases Visitor signature: ECollisionVisitorResult(FParticlePairMidPhase&)

Operators

  Type Name Description
Public function FCollisionConstraintAllocator &  
Public function FCollisionConstraintAllocator &  

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