The grasping function has captured objects outside the range

[kong2456878740]

Problem description

Hello, recently I encountered some issues while testing the scraping function of this library. In the source code of setGrabAction, it seems that a sphere is created in hand and collided with the model in the scene for detection to determine if the model can be grabbed. During the test, I imported a model in the.j3o format. However, during the testing process, it is still possible to pick up the model from a far distance outside the bounding box range of the model. But this usually only occurs when the object is picked up for the first time after the project runs. But when I perform this operation on the directly created box, this problem does not occur. I hope to get your clarification.

Operating Environment

tamarin 3.0.1
jdk 22

Code

public class VRTest extends BaseApp {
    public static void main(String[] args) {
        AppSettings settings = new AppSettings(true);
        //settings.setSamples(4);
        //settings.setResolution(1280,960);
        settings.setWindowSize(1280, 720);
        settings.put("Renderer", AppSettings.LWJGL_OPENGL45);
        settings.setTitle("Tamarin OpenXR Example");
        settings.setVSync(false);
        VRTest app = new VRTest();
        app.setLostFocusBehavior(LostFocusBehavior.Disabled);
        app.setSettings(settings);
        app.setShowSettings(false);
        app.start();
    }

 @Override
    public void simpleInitApp(){
        Spatial shell = assetManager.loadModel("shell.j3o");
        sceneNode = new Node("sceneNode");
        sceneNode.attachChild(shell);
        RelativeMovingGrabControl grabControl = new RelativeMovingGrabControl();
        shell.addControl(grabControl);
        rootNode.attachChild(sceneNode);
    }

 @Override
    public void simpleUpdate(float tpf) {
        if (!grabActionBound) {
            if (!vrHandsAppState.getHandControls().isEmpty()) {
                vrHandsAppState.getHandControls().forEach(boundHand ->
                        boundHand.setGrabAction(ActionHandles.GRIP, rootNode));
                grabActionBound = true;
            }
        }
    ｝
｝

Attachment

shell.zip

[oneMillionWorlds]

Hi @kong2456878740 , I've had a look and I think there is something wrong with the shell geometry itself. I've set up this test without Tamarin in the loop and it detects part of the geometry far away from its visible location

public class ModelDebug extends SimpleApplication {
    public static void main(String[] args) {
        ModelDebug app = new ModelDebug();
        app.start();
    }

    private Node sceneNode;

    Spatial shell;

    Vector3f scanPosition = new Vector3f(0.13157707f, 1.0809497f, 9.927096f);

    @Override
    public void simpleInitApp() {
        viewPort.setBackgroundColor(ColorRGBA.White);
        
        shell = getAssetManager().loadModel("Models/shell.j3o");

        sceneNode = new Node("sceneNode");
        sceneNode.attachChild(shell);
        rootNode.attachChild(sceneNode);

        getCamera().lookAt(shell.getWorldTranslation(), Vector3f.UNIT_Y);

        DirectionalLight dl = new DirectionalLight();
        dl.setColor(ColorRGBA.White);
        dl.setDirection(new Vector3f(-5f, -5f, -5f));
        rootNode.addLight(dl);

        AmbientLight al = new AmbientLight();
        al.setColor(ColorRGBA.White.mult(0.5f));
        rootNode.addLight(al);

        testSphere();
        placeDebugCube();

        getCamera().setLocation(new Vector3f(0, 2, 12));
        getCamera().lookAt(scanPosition, Vector3f.UNIT_Y);
    }

    private void testSphere() {

        BoundingSphere sphere = new BoundingSphere(0.02f, scanPosition);
        CollisionResults results = new CollisionResults();

        rootNode.collideWith(sphere, results);
        if(results.size()>0) {
            System.out.println("Hit at position: " + scanPosition);
            for(int i=0; i<results.size(); i++) {
                System.out.println(results.getCollision(i).getGeometry().getName());
            }
        }
    }

    private void placeDebugCube(){
        Box cubeBox = new Box(0.1f, 0.1f, 0.1f);
        Geometry cubeGeom = new Geometry("Debug", cubeBox);
        cubeGeom.setLocalTranslation(scanPosition);

        Material mat = new Material(getAssetManager(), "Common/MatDefs/Misc/Unshaded.j3md");
        mat.setColor("Color", ColorRGBA.Green);
        cubeGeom.setMaterial(mat);
        sceneNode.attachChild(cubeGeom);
    }
}

This prints:

Hit at position: (0.13157707, 1.0809497, 9.927096)
32:a6d31b0349cf42ab973ffa53f1a363a5

[oneMillionWorlds]

I tried doing a point search around that point for where did and didn't report hits and I got this

But I can expand it further and loads of random points seem to report containing the model. Here is the same thing at lower test res but over a larger area

This is the scanning code

    private void scanModel(Vector3f minimumScan, Vector3f maximumScan, float resolution ) {
        for (float x = minimumScan.x; x <= maximumScan.x; x += resolution) {
            for (float y = minimumScan.y; y <= maximumScan.y; y += resolution) {
                for (float z = minimumScan.z; z <= maximumScan.z; z += resolution) {
                    Vector3f scanPosition = new Vector3f(x, y, z);

                    BoundingSphere sphere = new BoundingSphere(0.02f, scanPosition);
                    CollisionResults results = new CollisionResults();
                    shell.collideWith(sphere, results);

                    if (results.size() > 0) {
                        // Hit detected - place a red cube at this position
                        Box cubeBox = new Box(resolution / 2f, resolution / 2f, resolution / 2f);
                        Geometry cubeGeom = new Geometry("HitCube", cubeBox);
                        cubeGeom.setLocalTranslation(scanPosition);

                        Material mat = new Material(getAssetManager(), "Common/MatDefs/Misc/Unshaded.j3md");
                        mat.setColor("Color", ColorRGBA.Red);
                        cubeGeom.setMaterial(mat);

                        sceneNode.attachChild(cubeGeom);

                    }
                }
            }
        }
    }

[kong2456878740]

Hello, I also encountered similar issues when conducting line-to-surface collision detection in jmonkeyengine before. So, I wondered if it might be a problem with the collision detection. I obtained the object that the scanning ball collided with and generated its bounding box, then extracted some of the parameters. Some of the data were quite perplexing. When the coordinates of the scanning sphere are (4.950001, 1.2499999, 4.950001), the distance from it to the collision object is distToBB=4.9667716, but the radius of the scanning sphere is only 0.02.

    private void scanModel(Vector3f minimumScan, Vector3f maximumScan, float resolution ) {
        for (float x = minimumScan.x; x <= maximumScan.x; x += resolution) {
            for (float y = minimumScan.y; y <= maximumScan.y; y += resolution) {
                for (float z = minimumScan.z; z <= maximumScan.z; z += resolution) {
                    Vector3f scanPosition = new Vector3f(x, y, z);

                    BoundingSphere sphere = new BoundingSphere(0.02f, scanPosition);
                    CollisionResults results = new CollisionResults();
                    shell.collideWith(sphere, results);

                    float r = 0.02f;

                    if (results.size() > 0) {

                        var col = results.getClosestCollision();
                        Geometry hit = col.getGeometry();

                        BoundingBox bb = (BoundingBox) hit.getWorldBound();
                        float d = distancePointToAABB(scanPosition, bb);

                        if (d > r + 1e-4f) {
                            System.out.println("FALSE HIT? scan=" + scanPosition
                                    + " geom=" + hit.getName()
                                    + " distToBB=" + d
                                    + " r=" + r
                                    + " bbCenter=" + bb.getCenter()
                                    + " bbExt=" + bb.getExtent(null)
                                    + " contact=" + col.getContactPoint());
                        }

                        System.out.println("hit worldScale=" + hit.getWorldScale()
                                + " worldTrans=" + hit.getWorldTranslation());

                        // Hit detected - place a red cube at this position
                        Box cubeBox = new Box(resolution / 2f, resolution / 2f, resolution / 2f);
                        Geometry cubeGeom = new Geometry("HitCube", cubeBox);
                        cubeGeom.setLocalTranslation(scanPosition);

                        Material mat = new Material(getAssetManager(), "Common/MatDefs/Misc/Unshaded.j3md");
                        mat.setColor("Color", ColorRGBA.Red);
                        cubeGeom.setMaterial(mat);

                        sceneNode.attachChild(cubeGeom);

                    }
                }
            }
        }
    }

    private static float distancePointToAABB(Vector3f p, BoundingBox bb) {
        Vector3f c = bb.getCenter();
        Vector3f e = bb.getExtent(null);

        float dx = Math.max(0f, Math.abs(p.x - c.x) - e.x);
        float dy = Math.max(0f, Math.abs(p.y - c.y) - e.y);
        float dz = Math.max(0f, Math.abs(p.z - c.z) - e.z);

        return (float)Math.sqrt(dx*dx + dy*dy + dz*dz);
    }

[oneMillionWorlds]

Yeah, there is definitely something weird going on. How was the j3o created? Does the raw model (before being converted to j3o) have these issues?

I would suggest take the issue to https://hub.jmonkeyengine.org/ (Maybe with the self contained test I created?), see if a wider audience spots something

[kong2456878740]

Hello, I'm sorry that I couldn't obtain the original model. However, I did attempt to export it in the .obj format, and the same issue occurred. But after I processed it using 3D alpha shapes, this problem disappeared. Thank you very much for your explanation. Once I find the solution, I will remember to inform you. Finally, I wish you a happy New Year.