Particles and shapes

Particles

About

• X represents the location of the particle
• R represents the rotation of the particle.
• V represents the linear velocity of the particle
• W represents the angular velocity of the particle.
• M represents the mass of the particle.

flowchart TD


    IPhysicsProxyBase --> TPhysicsProxy
    IPhysicsProxyBase --> FSingleParticlePhysicsProxy
    FPhysicsObject
    TPhysicsProxy --> FGeometryCollectionPhysicsProxy
    FSingleParticlePhysicsProxy --> TThreadedSingleParticlePhysicsProxyBase
    TParticleHandleBase --> FGeometryParticleHandle[FGeometryParticleHandle TGeometryParticleHandle, TGeometryParticleHandleImp]
    TPhysicsProxy --> FSkeletalMeshPhysicsProxy

FPhysicsActorHandle (FSingleParticlePhysicsProxy)

Each Body Instance has a reference to a FPhysicsActorHandle. See Body Instance. From the FSingleParticlePhysicsProxy you can get its internal (GetPhysicsThreadAPI) and external (GetGameThreadAPI) rigid body handle.

It holds an FParticleHandle, alias of FGeometryParticleHandle.

FPhysicsObjectHandle (FPhysicsObject)

The FPhysicsObject is effectively a reference to a single particle in the solver.
It maintains this reference indirectly via the physics proxy. This object is meant to be usable on both the game thread and physics thread.

It holds a ref to IPhysicsProxyBase* Proxy, int32 BodyIndex and FName BodyName. So for example you can have multiple FPhysicsObjects which has the same SKM proxy but have different body indexes and body names.

FGeometryParticleHandle (TGeometryParticleHandle, TGeometryParticleHandleImp)

TParticleHandleBase

IPhysicsProxyBase

TPhysicsProxy

Base object interface for solver objects. Defines the expected API for objects, uses CRTP for static dispatch, entire API considered “pure-virtual” and must be defined.
Forgetting to implement any of the interface functions will give errors regarding recursion on all control paths for TPhysicsProxy<T> where T will be the type that has not correctly implemented the API.

PersistentTask uses IPhysicsProxyBase, so when implementing a new specialized type it is necessary to include its header file in PersistentTask.cpp allowing the linker to properly resolve the new type.

TThreadedSingleParticlePhysicsProxyBase

Wrapper class that routes all reads and writes to the appropriate particle data. This is helpful for cases where we want to both write to a particle and a network buffer for example.

TThreadParticle (FGeometryParticle, FGeometryParticleHandle)

It is an alias of FGeometryParticle if the thread is external or of type FGeometryParticleHandle if the thread is internal.

Shapes

FShapeInstanceProxy

FShapeInstanceProxy is a Game-Thread object.

It contains the per-shape data associated with a single shape on a particle. This contains data like the collision / query filters, material properties etc.

Every particle holds one FShapeInstanceProxy object for each geometry they use.
If the particle has a Union of geometries there will be one FShapeInstanceProxy for each geometry in the union. (Except ClusteredUnions - these are not flattened because they contain their own query acceleration structure.)

FShapeInstance

FShapeInstance is a Physics-Thread object.

It contains the per-shape data associated with a single shape on a particle. This contains data like the collision / query filters, material properties etc.

Every particle holds one FShapeInstance object for each geometry they use. If the particle has a Union of geometries there will be one FShapeInstance for each geometry in the union. (Except ClusteredUnions - these are not flattened because they contain their own query acceleration structure.)

FPerShapeData

FPerShapeData is going to be deprecated. See FShapeInstance and FShapeInstanceProxy. This is still used in engine as 5.6