How to Define World Bound for PhysX in UE4?

Question

I am trying to use PxBroadPhaseType::eMBP alogrithm for my ue4 project.

As the document mentioned:

PxBroadPhaseType::eMBP is a new algorithm introduced in PhysX 3.3. It is an alternative broad-phase algorithm that does not suffer from the same performance issues as eSAP when all objects are moving or when inserting large numbers of objects. However its generic performance when many objects are sleeping might be inferior to eSAP, and it requires users to define world bounds in order to work.

But where can I define the world bounds? I cannot find such variable in PxSceneDesc or PxScene.

score 0 · Accepted Answer · answered Nov 21 '18 at 18:31

Folllowing this article : https://wessamfathi.com/2018/04/17/the-case-of-million-collision-bodies/ it seems to me that you need to define PxBroadPhaseRegion and add them to your scene.

 if (UPhysicsSettings::Get()->bEnableMBPForBroadphase)
{
    PSceneDesc.broadPhaseType = PxBroadPhaseType::eMBP;
}

bool bIsValid = PSceneDesc.isValid();
if (!bIsValid)
{
    UE_LOG(LogPhysics, Log, TEXT("Invalid PSceneDesc"));
}

// Create scene, and add to map
PxScene* PScene = GPhysXSDK->createScene(PSceneDesc);

if (UPhysicsSettings::Get()->bEnableMBPForBroadphase && PScene->getBroadPhaseType())
{
    TArray<PxBounds3> Regions;
    const uint32 SubDivs = UPhysicsSettings::Get()->MBPRegionSubdiv;
    Regions.SetNumUninitialized(SubDivs * SubDivs);

    const PxBounds3 LevelBounds = PxBounds3::centerExtents(PxVec3(PxZero), U2PVector(UPhysicsSettings::Get()->MBPWorldBounds));

    PxU32 Num = PxBroadPhaseExt::createRegionsFromWorldBounds(Regions.GetData(), LevelBounds, SubDivs, 2);
    check(Num == SubDivs * SubDivs);

    for (const PxBounds3& Bounds : Regions)
    {
        PxBroadPhaseRegion Region;
        Region.bounds = Bounds;
        Region.userData = nullptr;
        PScene->addBroadPhaseRegion(Region);
    }
}

How to Define World Bound for PhysX in UE4?

1 Answers1