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Mastering Development

didBeginContact delegate method not firing for ARKit collision detection

I can’t get the didBeginContact method to fire, I have been trying for a while and I can’t spot the error, could use a fresh set of eyes:

- (void)viewDidLoad {
    [super viewDidLoad];
    self.lastRender = nil;
    self.accelX = 0.0;
    self.accelY = 0.0;
    self.accelZ = 0.0;
    self.isLooping = TRUE;
    self.tripWire = TRUE;
    self.lastPaddleNode = [[SCNNode alloc] init];

    self.paddleNode = [[SCNNode alloc] init];
    SCNPlane* paddlePlane = [SCNPlane planeWithWidth:0.067056 height:0.138176];
    self.paddleNode.geometry = paddlePlane;
    self.paddleNode.geometry.firstMaterial.diffuse.contents = [UIColor colorWithRed:133.0/255.0f green:158.0/255.0f blue:122.0/255.0f alpha:0.8];
    self.paddleNode.simdTransform = matrix_identity_float4x4;
    self.paddleNode.name = @"paddle";

    SCNPhysicsBody* paddlePhys = [[SCNPhysicsBody alloc] init];
    paddlePhys.type = SCNPhysicsBodyTypeDynamic;
    paddlePhys.physicsShape = [SCNPhysicsShape shapeWithGeometry:paddlePlane options:nil];
    //paddlePhys.affectedByGravity = FALSE;
    paddlePhys.categoryBitMask = SCNPhysicsCollisionCategoryAll;
    paddlePhys.collisionBitMask = SCNPhysicsCollisionCategoryAll;
    paddlePhys.contactTestBitMask = SCNPhysicsCollisionCategoryAll;
    paddlePhys.usesDefaultMomentOfInertia = TRUE;
    self.paddleNode.physicsBody = paddlePhys;

    SCNNode* ball = [[SCNNode alloc] init];
    SCNPhysicsBody* phys = [[SCNPhysicsBody alloc] init];
    phys.type = SCNPhysicsBodyTypeDynamic;
    SCNSphere* sphere = [SCNSphere sphereWithRadius:0.067f];
    phys.physicsShape = [SCNPhysicsShape shapeWithGeometry:sphere options:nil];
    ball.geometry = sphere;
    ball.geometry.firstMaterial.diffuse.contents = [UIColor yellowColor];
    //phys.affectedByGravity = FALSE;
    phys.categoryBitMask = SCNPhysicsCollisionCategoryAll;
    phys.collisionBitMask = SCNPhysicsCollisionCategoryAll;
    phys.contactTestBitMask = SCNPhysicsCollisionCategoryAll;
    phys.usesDefaultMomentOfInertia = TRUE;
    phys.velocityFactor = SCNVector3Make(10.0, 10.0, 10.0);
    ball.physicsBody = phys;
    ball.physicsBody.continuousCollisionDetectionThreshold = 0.134f;
    ball.simdPosition = simd_make_float3(0.0, 0.27, -0.27);
    ball.name = @"ball";
    //phys.velocityFactor = SCNVector3Make(10, 10, 10);

    [self.sceneView setPreferredFramesPerSecond:60];

    self.locationManager = [[CLLocationManager alloc] init];
    self.locationManager.delegate = self;
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;

    // Set the view's delegate
    self.sceneView.delegate = self;

    // Show statistics such as fps and timing information
    self.sceneView.showsStatistics = YES;

    //phys.velocityFactor = SCNVector3Make(10, 10, 10);

    // Create a new scene
    SCNScene* scene = [[SCNScene alloc] init];
    scene.physicsWorld.contactDelegate = self;
    self.sceneView.scene = scene;

    [locationManager startUpdatingHeading];

    while(!(self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 359)) {

        NSLog(@"heading: %f", self.locationManager.heading.trueHeading);

        if (self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 359) {
            break;
        }
    }

    [self.sceneView.scene.rootNode addChildNode:self.paddleNode];
    [self.sceneView.scene.rootNode addChildNode:ball];

    [self startUpdates];
}

All I am trying to do write now is the delegate method to fire when the two nodes in my game collide:

- (void)physicsWorld:(SCNPhysicsWorld *)world didBeginContact:(SCNPhysicsContact *)contact {
    NSLog(@"in didBeginContact");
    CollisionCategory contactMask =
        contact.nodeA.physicsBody.categoryBitMask | contact.nodeB.physicsBody.categoryBitMask;

    // first, sort out what kind of collision
    if (contactMask == (CollisionCategoryPaddle | CollisionCategoryBall)) {
        // next, sort out which body is the missile and which is the rocket
        // and do something about it
        if (contact.nodeA.physicsBody.categoryBitMask == CollisionCategoryPaddle) {
            NSLog(@"nodeA is paddle!");
            //[self hitRocket:contact.nodeB withMissile:contact.nodeA];
        } else {
            NSLog(@"nodeB is paddle!");
            //[self hitRocket:contact.nodeA withMissile:contact.nodeB];
        }
    }
}

Note
I am aware that I am using SCNPhysicsCollisionCategoryAll and then checking for a different kind of bitmask in the method. That is not my problem, my problem is before that, I never see this log statement, which is the first line in my didBeginContact delegate method:

NSLog(@"in didBeginContact");

Why isn’t my method firing? I think I set the delegate correctly. Thanks.

UPDATE
My viewDidLoad looks like this now, per commenter’s suggestion:

- (void)viewDidLoad {
    [super viewDidLoad];
    // Create a new scene
    SCNScene* scene = [[SCNScene alloc] init];
    scene.physicsWorld.contactDelegate = self;
    self.sceneView.scene = scene;
    // Set the view's delegate
    self.sceneView.delegate = self;

    SCNPlane* paddlePlane = [SCNPlane planeWithWidth:0.067056 height:0.138176];
    self.paddleNode = [SCNNode nodeWithGeometry:paddlePlane];
    self.paddleNode.geometry.firstMaterial.diffuse.contents = [UIColor colorWithRed:133.0/255.0f green:158.0/255.0f blue:122.0/255.0f alpha:0.8];
    self.paddleNode.simdTransform = matrix_identity_float4x4;
    self.paddleNode.name = @"paddle";
    [self.sceneView.scene.rootNode addChildNode:self.paddleNode];

    SCNPhysicsBody* paddlePhys = [[SCNPhysicsBody alloc] init];
    paddlePhys.type = SCNPhysicsBodyTypeDynamic;
    paddlePhys.physicsShape = [SCNPhysicsShape shapeWithGeometry:self.paddleNode.geometry options:@{SCNPhysicsShapeTypeKey: SCNPhysicsShapeTypeBoundingBox}];
    //paddlePhys.affectedByGravity = FALSE;
    paddlePhys.categoryBitMask = SCNPhysicsCollisionCategoryAll;
    paddlePhys.collisionBitMask = SCNPhysicsCollisionCategoryAll;
    paddlePhys.contactTestBitMask = SCNPhysicsCollisionCategoryAll;
    //paddlePhys.usesDefaultMomentOfInertia = TRUE;
    self.paddleNode.physicsBody = paddlePhys;

    SCNNode* ball = [[SCNNode alloc] init];
    [self.sceneView.scene.rootNode addChildNode:ball];

    SCNPhysicsBody* phys = [[SCNPhysicsBody alloc] init];
    phys.type = SCNPhysicsBodyTypeDynamic;
    SCNSphere* sphere = [SCNSphere sphereWithRadius:0.067f];
    phys.physicsShape = [SCNPhysicsShape shapeWithGeometry:sphere options:@{SCNPhysicsShapeTypeKey: SCNPhysicsShapeTypeConvexHull}];
    ball.geometry = sphere;
    ball.geometry.firstMaterial.diffuse.contents = [UIColor yellowColor];
    //phys.affectedByGravity = FALSE;
    phys.categoryBitMask = SCNPhysicsCollisionCategoryAll;
    phys.collisionBitMask = SCNPhysicsCollisionCategoryAll;
    phys.contactTestBitMask = SCNPhysicsCollisionCategoryAll;
    phys.usesDefaultMomentOfInertia = TRUE;
    phys.velocityFactor = SCNVector3Make(10.0, 10.0, 10.0);
    ball.physicsBody = phys;
    ball.physicsBody.continuousCollisionDetectionThreshold = 0.134f;
    ball.simdPosition = simd_make_float3(0.0, 0.27, -0.27);
    ball.name = @"ball";

    //phys.velocityFactor = SCNVector3Make(10, 10, 10);

    // Show statistics such as fps and timing information
    self.sceneView.showsStatistics = YES;

    self.locationManager = [[CLLocationManager alloc] init];
    self.locationManager.delegate = self;
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;

    [locationManager startUpdatingHeading];

    while(!(self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 358)) {

        NSLog(@"heading: %f", self.locationManager.heading.trueHeading);

        if (self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 358) {
            break;
        }
    }

    [self.sceneView setPreferredFramesPerSecond:60];

    self.lastRender = nil;
    self.accelX = 0.0;
    self.accelY = 0.0;
    self.accelZ = 0.0;
    self.isLooping = TRUE;
    self.tripWire = TRUE;
    self.lastPaddleNode = [[SCNNode alloc] init];

    [self startUpdates];
}

I do agree with the commenter that this is probably a problem with how things are ordered here, I just can’t see what it is…helllppp, I’m droowwnnninng…

UPDATE
I changed my bitwise masks as follows, I didn’t use a custom enum type because I only have two objects, so I think I can just use ...All and ...Default, but it isn’t working like this. I will try custom enum type when I understand the bitwise AND operation, if someone could explain to me the left handed/right handed part, and how to do the operation?

//Paddle
paddlePhys.categoryBitMask = SCNPhysicsCollisionCategoryDefault;
paddlePhys.collisionBitMask = SCNPhysicsCollisionCategoryAll;
paddlePhys.contactTestBitMask = SCNPhysicsCollisionCategoryAll;

...

//Ball
phys.categoryBitMask = SCNPhysicsCollisionCategoryAll;
phys.collisionBitMask = SCNPhysicsCollisionCategoryDefault;
phys.contactTestBitMask = SCNPhysicsCollisionCategoryDefault;

Should this work? I also have my paddle set like this now:

paddlePhys.type = SCNPhysicsBodyTypeKinematic;
paddlePhys.physicsShape = [SCNPhysicsShape shapeWithGeometry:self.paddleNode.geometry options:@{SCNPhysicsShapeTypeKey: SCNPhysicsShapeTypeBoundingBox}];

My ball is this:

phys.type = SCNPhysicsBodyTypeDynamic;
phys.physicsShape = [SCNPhysicsShape shapeWithGeometry:sphere options:@{SCNPhysicsShapeTypeKey: SCNPhysicsShapeTypeConvexHull}];

All together right now I have:

- (void)viewDidLoad {
    [super viewDidLoad];

    self.sceneView.delegate = self;

    // Show statistics such as fps and timing information
    self.sceneView.showsStatistics = YES;

    SCNScene* scene = [[SCNScene alloc] init];

    // Create a new scene
    SCNPlane* paddlePlane = [SCNPlane planeWithWidth:0.067056 height:0.138176];
    paddlePlane.firstMaterial.doubleSided = YES;
    self.paddleNode = [SCNNode nodeWithGeometry:paddlePlane];
    self.paddleNode.geometry.firstMaterial.diffuse.contents = [UIColor colorWithRed:133.0/255.0f green:158.0/255.0f blue:122.0/255.0f alpha:0.8];
    self.paddleNode.simdTransform = matrix_identity_float4x4;
    self.paddleNode.name = @"paddle";

    SCNPhysicsBody* paddlePhys = [[SCNPhysicsBody alloc] init];
    paddlePhys.type = SCNPhysicsBodyTypeKinematic;
    paddlePhys.physicsShape = [SCNPhysicsShape shapeWithGeometry:self.paddleNode.geometry options:@{SCNPhysicsShapeTypeKey: SCNPhysicsShapeTypeBoundingBox}];
    //paddlePhys.affectedByGravity = FALSE;
    paddlePhys.categoryBitMask = SCNPhysicsCollisionCategoryDefault;
    paddlePhys.collisionBitMask = SCNPhysicsCollisionCategoryAll;
    paddlePhys.contactTestBitMask = SCNPhysicsCollisionCategoryAll;
    //paddlePhys.usesDefaultMomentOfInertia = TRUE;
    self.paddleNode.physicsBody = paddlePhys;

    self.paddleNode.simdPivot = [self makeTranslationMatrix:0 ty: 0 tz:0.1];

    SCNNode* ball = [[SCNNode alloc] init];

    SCNPhysicsBody* phys = [[SCNPhysicsBody alloc] init];
    SCNSphere* sphere = [SCNSphere sphereWithRadius:0.067f];
    phys.type = SCNPhysicsBodyTypeDynamic;
    phys.physicsShape = [SCNPhysicsShape shapeWithGeometry:sphere options:@{SCNPhysicsShapeTypeKey: SCNPhysicsShapeTypeConvexHull}];
    ball.geometry = sphere;
    ball.geometry.firstMaterial.diffuse.contents = [UIColor yellowColor];
    //phys.affectedByGravity = FALSE;
    phys.categoryBitMask = SCNPhysicsCollisionCategoryAll;
    phys.collisionBitMask = SCNPhysicsCollisionCategoryDefault;
    phys.contactTestBitMask = SCNPhysicsCollisionCategoryDefault;
    phys.usesDefaultMomentOfInertia = TRUE;
    phys.velocityFactor = SCNVector3Make(10.0, 10.0, 10.0);
    ball.physicsBody = phys;
    ball.physicsBody.continuousCollisionDetectionThreshold = 0.134f;
    ball.simdPosition = simd_make_float3(0.0, 0.27, -0.27);
    ball.name = @"ball";

    self.locationManager = [[CLLocationManager alloc] init];
    self.locationManager.delegate = self;
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;

    [locationManager startUpdatingHeading];

    while(!(self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 358)) {

        NSLog(@"heading: %f", self.locationManager.heading.trueHeading);

        if (self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 358) {
            break;
        }
    }

    [self.sceneView setPreferredFramesPerSecond:60];

    self.lastRender = nil;
    self.accelX = 0.0;
    self.accelY = 0.0;
    self.accelZ = 0.0;
    self.isLooping = TRUE;
    self.tripWire = TRUE;
    self.lastPaddleNode = [[SCNNode alloc] init];

    [scene.rootNode addChildNode:ball];
    [scene.rootNode addChildNode:self.paddleNode];

    scene.physicsWorld.contactDelegate = self;
    self.sceneView.scene = scene;

    [self startUpdates];
}

I am also wondering if the problem might be in the block for the CMDeviceMotion events, here is that:

- (void)startUpdates {
    //dispatch_queue_t myQueue = dispatch_queue_create("com.eamon.corona_pong", DISPATCH_QUEUE_SERIAL);
    // Determine the update interval.
    NSTimeInterval updateInterval = 1.0/60.0;
    // Create a CMMotionManager object.
    CMMotionManager *mManager = [(AppDelegate *)[[UIApplication sharedApplication] delegate] sharedManager];
    if ([mManager isDeviceMotionAvailable] == YES) {
        [mManager setDeviceMotionUpdateInterval:updateInterval];
        // do something appropriate here
        if ([CMMotionManager availableAttitudeReferenceFrames] & CMAttitudeReferenceFrameXTrueNorthZVertical) {

            [mManager startDeviceMotionUpdatesUsingReferenceFrame:CMAttitudeReferenceFrameXArbitraryCorrectedZVertical toQueue:[NSOperationQueue mainQueue] withHandler:^(CMDeviceMotion * _Nullable motion, NSError * _Nullable error) {
                //[self handleMotionWrapper:motion];
                [SCNTransaction begin];
                [SCNTransaction setAnimationDuration:0];
                //simd_float4x4 rotateY = [self makeYRotationMatrix:270.0];
                //simd_float4x4 rotate = [self makeXRotationMatrix:270.0];

                simd_float4x4 cameraTrans = self.sceneView.session.currentFrame.camera.transform;

                simd_float4x4 temp = simd_mul(cameraTrans, [self makeYRotationMatrix:270.0]);

                //simd_float4x4 rotated = simd_mul(temp, [self makeYRotationMatrix:135]);

                simd_float4x4 transMatrixMotion = [self makeTranslationMatrix:self.lastPaddleNode.simdPosition.x ty:self.lastPaddleNode.simdPosition.y - 0.1 tz:self.lastPaddleNode.simdPosition.z];

                self.paddleNode.simdPosition = simd_make_float3(simd_mul(simd_make_float4(temp.columns[3][0], temp.columns[3][1], temp.columns[3][2], 1.0), transMatrixMotion));

                self.paddleNode.simdTransform = temp;
                [SCNTransaction commit];

                self.lastPaddleNode = self.paddleNode;
                self.tripWire = FALSE;
            }];
        }
    }
}

I’m am still working out the motion code, but I figure the collision should work, even though I don’t have the paddle oriented exactly how I want yet (I just need to rotate it 90 degrees around the y-axis, but it is proving to be annoying, but shouldn’t matter for collision detection, right?)

Also, what about SCNPlane, I also made my SCNPlane (the paddle) double-sided with the doubleSided attribute of the firstMaterial attribute but it did not help, maybe I need to use a shallow SCNBox? I have tried it before, but maybe some of the changes I have made would mean it would work if I make my paddle and SCNBox instead of a double-sided SCNPlane?

THANKS!

UPDATE
I thought I would share my latest attempt, doesn’t work but I think it might be closer, might be easier to spot the problem:

typedef NS_OPTIONS(NSUInteger, CollisionCategory)
{
    CollisionCategoryPaddle = 1 << 0,
    CollisionCategoryBall = 1 << 1,
};

- (void)viewDidLoad {
    [super viewDidLoad];

    self.sceneView.delegate = self;

    // Show statistics such as fps and timing information
    self.sceneView.showsStatistics = YES;

    SCNScene* scene = [[SCNScene alloc] init];
    self.sceneView.scene = scene;
    self.sceneView.scene.physicsWorld.contactDelegate = self;
    // Create a new scene
    SCNBox* paddlePlane = [SCNBox boxWithWidth:0.067056 height:0.138176 length:0.01 chamferRadius:0.0];
    paddlePlane.firstMaterial.doubleSided = YES;
    self.paddleNode = [SCNNode nodeWithGeometry:paddlePlane];
    self.paddleNode.geometry.firstMaterial.diffuse.contents = [UIColor colorWithRed:133.0/255.0f green:158.0/255.0f blue:122.0/255.0f alpha:0.8];
    self.paddleNode.simdTransform = matrix_identity_float4x4;
    self.paddleNode.name = @"paddle";

    [self.sceneView.scene.rootNode addChildNode:self.paddleNode];

    SCNPhysicsBody* paddlePhys = [[SCNPhysicsBody alloc] init];
    paddlePhys.type = SCNPhysicsBodyTypeKinematic;
    paddlePhys.physicsShape = [SCNPhysicsShape shapeWithGeometry:self.paddleNode.geometry options:nil];
    //paddlePhys.affectedByGravity = FALSE;
    paddlePhys.categoryBitMask = CollisionCategoryPaddle;
    paddlePhys.collisionBitMask = CollisionCategoryBall;
    paddlePhys.contactTestBitMask = CollisionCategoryBall;
    //paddlePhys.usesDefaultMomentOfInertia = TRUE;
    self.paddleNode.physicsBody = paddlePhys;

    SCNPhysicsBody* phys = [[SCNPhysicsBody alloc] init];
    SCNSphere* sphere = [SCNSphere sphereWithRadius:0.067f];
    self.ballNode = [[SCNNode alloc] init];
    self.ballNode.name = @"ball";
    self.ballNode.geometry = sphere;
    self.ballNode.geometry.firstMaterial.diffuse.contents = [UIColor yellowColor];
    //self.ballNode.physicsBody.continuousCollisionDetectionThreshold = (CGFloat)0.134f;
    self.ballNode.simdPosition = simd_make_float3(0.0, 0.27, -0.27);

    [self.sceneView.scene.rootNode addChildNode:self.ballNode];

    phys.type = SCNPhysicsBodyTypeDynamic;
    phys.physicsShape = [SCNPhysicsShape shapeWithGeometry:self.ballNode.geometry options:nil];
    phys.categoryBitMask = CollisionCategoryBall;
    phys.collisionBitMask = CollisionCategoryPaddle;
    phys.contactTestBitMask = CollisionCategoryPaddle;
    //phys.usesDefaultMomentOfInertia = TRUE;
    //phys.velocityFactor = SCNVector3Make(10.0, 10.0, 10.0);
    self.ballNode.physicsBody = phys;

    //phys.affectedByGravity = FALSE

    self.locationManager = [[CLLocationManager alloc] init];
    self.locationManager.delegate = self;
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;

    [locationManager startUpdatingHeading];

    while(!(self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 358)) {

        NSLog(@"heading: %f", self.locationManager.heading.trueHeading);

        if (self.locationManager.heading.trueHeading <= 360 && self.locationManager.heading.trueHeading >= 358) {
            break;
        }
    }

    [self.sceneView setPreferredFramesPerSecond:60];

    self.lastRender = nil;
    self.accelX = 0.0;
    self.accelY = 0.0;
    self.accelZ = 0.0;
    self.isLooping = TRUE;
    self.tripWire = TRUE;
    self.lastPaddleNode = [[SCNNode alloc] init];

    [self startUpdates];
}

I tried this way too, althought I’m not sure if I am using it right:

phys.physicsShape = [SCNPhysicsShape shapeWithGeometry:self.ballNode.geometry options:@{SCNHitTestOptionCategoryBitMask:[NSNumber numberWithUnsignedInt:CollisionCategoryBall], SCNPhysicsTestCollisionBitMaskKey:[NSNumber numberWithUnsignedInt:CollisionCategoryPaddle]}];

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