Method createIslands

src/engine/PhysicsWorld.cpp:695–869

Compute the islands using potential contacts and joints We compute the islands before creating the actual contacts here because we want all the contact manifolds and contact points of the same island to be packed together into linear arrays of manifolds and contacts for better caching. An island is an isolated group of rigid bodies that have constraints (joints or contacts) between each other. Thi

/// find all the bodies that are connected with it (the bodies that share joints or contacts with
/// it). Then, we create an island with this group of connected bodies.
void PhysicsWorld::createIslands() {

    RP3D_PROFILE("PhysicsWorld::createIslands()", mProfiler);

    assert(mProcessContactPairsOrderIslands.size() == 0);

    // Reset all the isAlreadyInIsland variables of bodies and joints
    const uint32 nbRigidBodyComponents = mRigidBodyComponents.getNbComponents();
    for (uint32 b=0; b < nbRigidBodyComponents; b++) {
        mRigidBodyComponents.mIsAlreadyInIsland[b] = false;
    }
    const uint32 nbJointsComponents = mJointsComponents.getNbComponents();
    for (uint32 i=0; i < nbJointsComponents; i++) {
        mJointsComponents.mIsAlreadyInIsland[i] = false;
    }

    // Reserve memory for the islands
    mIslands.reserveMemory();

    // Create a stack for the bodies to visit during the Depth First Search
    Stack<Entity> bodyEntitiesToVisit(mMemoryManager.getSingleFrameAllocator(), mIslands.getNbMaxBodiesInIslandPreviousFrame());

    // Array of static bodies added to the current island (used to reset the isAlreadyInIsland variable of static bodies)
    Array<Entity> staticBodiesAddedToIsland(mMemoryManager.getSingleFrameAllocator(), 16);

    uint32 nbTotalManifolds = 0;

    // For each rigid body component
    for (uint32 b=0; b < mRigidBodyComponents.getNbEnabledComponents(); b++) {

        // If the body has already been added to an island, we go to the next body
        if (mRigidBodyComponents.mIsAlreadyInIsland[b]) continue;

        // If the body is static, we go to the next body
        if (mRigidBodyComponents.mBodyTypes[b] == BodyType::STATIC) continue;

        // If the body does not have any simulation collider, we skip it
        if (!mBodyComponents.getHasSimulationCollider(mRigidBodyComponents.mRigidBodies[b]->getEntity())) continue;

        // Reset the stack of bodies to visit
        bodyEntitiesToVisit.clear();

        // Add the body into the stack of bodies to visit
        mRigidBodyComponents.mIsAlreadyInIsland[b] = true;
        bodyEntitiesToVisit.push(mRigidBodyComponents.mBodiesEntities[b]);

        // Create the new island
        uint32 islandIndex = mIslands.addIsland(nbTotalManifolds);

        // While there are still some bodies to visit in the stack
        while (bodyEntitiesToVisit.size() > 0) {

            // Get the body entity
            const Entity bodyToVisitEntity = bodyEntitiesToVisit.pop();

            // Add the body into the island
            mIslands.addBodyToIsland(bodyToVisitEntity);