[Unresolved] PhysX safe Async operations

Physics
#1

In terrain generation tutorial, there is an async actor creation example: HOWTO: Create terrain from code | Flax Documentation

It runs without warning as it is, but just increasing patch counts from (2,2) to higher number creates physx errors in log window. I enabled Support Cooking At Runtime in options FYI.

I increased it to (16, 16) and met these thread collision errors:

[ 17:49:59.271 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:49:59.505 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:49:59.505 ]: [Error] PhysX Error! Code: 8.
PxShape::setQueryFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 385.
[ 17:49:59.954 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:50:00.004 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:50:00.121 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:50:00.321 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:50:00.538 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:50:00.538 ]: [Error] PhysX Error! Code: 8.
PxShape::setQueryFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 385.
[ 17:50:00.671 ]: [Error] PhysX Error! Code: 8.
PxScene::addActor() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpScene.cpp : 476.
[ 17:50:00.788 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 17:50:00.788 ]: [Error] PhysX Error! Code: 8.
PxShape::setQueryFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 385.

It would be nice to know the official way to ‘work properly with physics object asynchronously’ if exists.

#2

You need to remove actor from scene when it’s being edited prevent such issues. Simpyl set Parent = null and then add it back.

#3

Current :

    public override void OnStart()
    {
        // Create new dynamic terrain actor and add it to the scene
        _terrain = new Terrain();
        _terrain.HideFlags = HideFlags.DontSave;
        _terrain.Name = "My Terrain";
        _terrain.Setup();
        _terrain.Parent = Actor;

        // Generate terrain using the async task to prevent game stalls
        // You can also use C# thread to perform this work
        // Your game can display progress bar or loading screen while terrain is being generated
        Task.Run(new Action(GenerateTerrain));
    }

To : [Edit : this code is incorrect. Flax does not let actor modification outside of main thread]

    public override void OnStart()
    {
        // Create new dynamic terrain actor and add it to the scene
        _terrain = new Terrain();
        _terrain.HideFlags = HideFlags.DontSave;
        _terrain.Name = "My Terrain";
        _terrain.Setup();
        _terrain.Parent = null;

        // Generate terrain using the async task to prevent game stalls
        // You can also use C# thread to perform this work
        // Your game can display progress bar or loading screen while terrain is being generated
        Task.Run(new Action(GenerateTerrain)).ContinueWith(task => _terrain.Parent = Actor);
    }

Kind of?
I’ll try soon!

#4

I tested with the following code(still with the default template), I could see the terrain appears to the scene after it fully created.
(ContinueWith creates a task so it is not guaranteed to be in mainthread, so I ditched it by the kind error message)

Task t;

public override void OnStart()
{
    // Create new dynamic terrain actor and add it to the scene
    _terrain = new Terrain();
    _terrain.HideFlags = HideFlags.DontSave;
    _terrain.Name = "My Terrain";
    _terrain.Parent = null;
    _terrain.Setup();
    //_terrain.Parent = Actor;

    t = Task.Run(new Action(GenerateTerrain));
}


public override void OnUpdate()
{
    if (t.IsCompleted)
    {
        _terrain.Parent = Actor;
    }
}

But it still creates same PhysX error while in midst time of creation.

[ 00:26:06.199 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.

And aside of task completion check and parent assignment, terrain generation with Parent = null itself gives me PhysX error when enoughly large patch arrays applied. It means removing terrain completion and leaving it unparented forever makes the same result, so somehow Parent = null is insufficient for solving the physics problem.

Am I missing right way to set de-parenting the actor? Any help could be thankful.

[Edited]
Log says error occured from setSimulationFilterData() / PxShape::setQueryFilterData in PhysX engine call,

[ 00:12:32.597 ]: [Error] PhysX Error! Code: 8.
PxShape::setSimulationFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 364.
[ 00:12:33.797 ]: [Error] PhysX Error! Code: 8.
PxShape::setQueryFilterData() not allowed while simulation is running. Call will be ignored.
Source: F:\FlaxEngineDotnet\Cache\Intermediate\Deps\PhysX\physx\source\physx\src\NpShape.cpp : 385.

And that call is might be from UpdateLayerBits() in Terrain class (which calls PhysicsBackend::SetShapeFilterMask(), using both physX functions).

void Terrain::UpdateLayerBits()
{
…

// Update the shapes layer bits
for (int32 pathIndex = 0; pathIndex < _patches.Count(); pathIndex++)
{
    const auto patch = _patches[pathIndex];
    if (patch->HasCollision())
    {
        PhysicsBackend::SetShapeFilterMask(patch->_physicsShape, mask0, mask1);
    }
}

}

UpdateLayerBits() is called directly from AddPatches().

void Terrain::AddPatches(const Int2& numberOfPatches)
{
…

if (IsDuringPlay())
{
    ...
    UpdateLayerBits();
}

}

Physics access might not be visible right from the surface, but just from the call tree itself there is not much relation between render graph tree (parent = something problem) assignment and PxShape::setSimulationFilterData() function call.

I’m in curious…

#5

Could you remove _terrain.Parent = null; and link actor to level after terrain generation i nasync to be invoked in a main thread via: Scripting.InvokeOnUpdate(() => _terrain.Parent = Actor); ? Maybe it helps.

#6

Is this means queueing invoke at the end of the generation task? I’ll try!

#7

Unfortunately the error did not go away.
This is the base code modified with your hint.

private Terrain _terrain;

[Limit(1, 64), Tooltip("Terrain patches count (in each direction on XZ plane).")]
public Int2 PatchesCount = new Int2(16, 16);

public override void OnStart()
{
    // Create new dynamic terrain actor and add it to the scene
    _terrain = new Terrain();
    _terrain.HideFlags = HideFlags.DontSave;
    _terrain.Name = "My Terrain";
    _terrain.Setup();

    // Generate terrain using the async task to prevent game stalls
    // You can also use C# thread to perform this work
    // Your game can display progress bar or loading screen while terrain is being generated
    Task.Run(new Action(GenerateTerrain));
}

private void GenerateTerrain()
{
    var chunkSize = _terrain.ChunkSize;
    var heightMapSize = chunkSize * FlaxEngine.Terrain.PatchEdgeChunksCount + 1;
    var heightMapLength = heightMapSize * heightMapSize;
    var heightmap = new float[heightMapLength];

    _terrain.AddPatches(ref PatchesCount);

    for (int patchZ = 0; patchZ < PatchesCount.Y; patchZ++)
    {
        for (int patchX = 0; patchX < PatchesCount.X; patchX++)
        {
            // Generate heightmap (simple sine wave for example showcase)
            for (int z = 0; z < heightMapSize; z++)
            {
                for (int x = 0; x < heightMapSize; x++)
                {
                    heightmap[z * heightMapSize + x] = Mathf.Sin((float)x / chunkSize * Mathf.PiOverFour * 3.0f) * 3000.0f;
                }
            }

            // Initialize patch (virtual)
            var patchCoord = new Int2(patchX, patchZ);
            //_terrain.AddPatch(ref patchCoord);
            _terrain.SetupPatchHeightMap(ref patchCoord, heightmap, null, true);
        }
    }
    Scripting.InvokeOnUpdate(() => _terrain.Parent = Actor);
}

At first I thought problem was solved but it was my mistake while editing the source code.
With calling GenerateTerrain() by Task the issue is still there.

Putting everything aside,

  1. Remove _terrain.Parent = Actor; line
  2. Do not add InvokeOnUpdate() (Do not touch scene tree at all, from start to end)
  3. Just try to make a bit large terrain

Results PhysX error.

And in effort of isolating the error:

  1. _terrain.AddPatch() seems not the major reason of error
  2. delay inside task seems not affect the error
  3. Existance of _terrain.SetupPatchHeightMap() highly affects the occurance of error
    → But this is also the bottleneck of CPU calculation hang - cannot move to the main thread
#8

Fixed in Fix creating virtual terrain collision of actor that is not in a game · FlaxEngine/FlaxEngine@db8adf7 · GitHub

#9

Expecting for the next release!