SceneKit - Instant contact detection using physicsWorld.updateCollisionPairs()

Question

I am trying to determine if there is a possible contact in the path of rotating a node. My idea is to do an incremented rotation (for 90 deg i loop 10 times 9 degrees) and perform contact test each time. My issue is that even tho i am calling updateCollisionPairs() each time, the contacts are empty even when there is an object in the path. Here is a picture that illustrate it somehow (front facing):

I'm trying to rotate node A by 90 degrees, but before i need to check if the "path is clear" - in this case the node B is in the way so i'm expecting to get a hit with one or more of the incremental rotations.

Node A and Node B are both type .kinematic, with categoryBitMask 2

Normaly i am doing contact testing in the render loop (willRenderScene) after the physicsWorld simulation is updated, and this triggers fine, so i know my physicsBodies & contactBitmasks are set correctly, but in this specific case i can't wait for another loop to perform the contact detection for obvious reasons.

Code i tried so far:

    for i in 1...10 {
        nodeA.transform = SCNMatrix4Mult(nodeA.transform, SCNMatrix4MakeRotation(GameHelper.deg2rad(deg:90)/10, 0, 0, 1))
        nodeA.physicsBody.resetTransform()
        self.scnScene.physicsWorld.updateCollisionPairs()
        let contacts = self.scnScene.physicsWorld.contactTest(with: (nodeA.physicsBody)!, options: [SCNPhysicsWorld.TestOption.collisionBitMask:2])

        print(contacts)
        if contacts.count > 0 {
            print("CONTACT !!!!")
        }

    }

mike_t mike_t · Accepted Answer · 2017-11-26T08:52:24

Looks like i just missplaced the code, the above code works fine if it's placed within the renderer(:willRenderScene) - i initialy tried to perform it directly within the method triggered by gestureRecogniser. Instead i just set the flag now and perform the check before next frame is rendered:

func renderer(_ renderer: SCNSceneRenderer, willRenderScene scene: SCNScene, atTime time: TimeInterval) {
    ... check for flag and perform contact test
}

SceneKit - Instant contact detection using physicsWorld.updateCollisionPairs()

1 Answers