Wall collisions in scene kit - objective-c

Question

I'm trying to write a game where a node can move about but is contained by a series of walls- basically a maze game. Just to get the basic thing going I pulled apart Apple's SceneKitVehicle project (https://developer.apple.com/library/ios/samplecode/SceneKitVehicle) to just the basic elements and put in a cube (the box node in the code below) instead of the physics vehicle in the original code.
Problem is, I programmatically move the box node until it reaches the wall and it just continues straight through the wall without stopping. Meanwhile, I can put the vehicle code back in and that DOES stop when it reaches the wall.
- (void)setupEnvironment:(SCNScene *)scene
{
//floor
SCNNode*floor = [SCNNode node];
floor.geometry = [SCNFloor floor];
floor.geometry.firstMaterial.diffuse.contents = #"wood.png";
SCNPhysicsBody *staticBody = [SCNPhysicsBody staticBody];
floor.physicsBody = staticBody;
[[scene rootNode] addChildNode:floor];
}
- (void)moveBox
{
SCNAction *moveByAction = [SCNAction moveByX:0 y:0 z:-3 duration:0.1];
SCNAction *repeatAction = [SCNAction repeatActionForever:moveByAction];
[_boxNode runAction:repeatAction];
}
- (void)setupSceneElements:(SCNScene *)scene
{
// add walls
SCNNode *wall = [SCNNode nodeWithGeometry:[SCNBox boxWithWidth:400 height:100 length:4 chamferRadius:0]];
wall.geometry.firstMaterial.diffuse.contents = #"wall.jpg";
wall.geometry.firstMaterial.diffuse.contentsTransform = SCNMatrix4Mult(SCNMatrix4MakeScale(24, 2, 1), SCNMatrix4MakeTranslation(0, 1, 0));
wall.geometry.firstMaterial.diffuse.wrapS = SCNWrapModeRepeat;
wall.geometry.firstMaterial.diffuse.wrapT = SCNWrapModeMirror;
wall.geometry.firstMaterial.doubleSided = NO;
wall.castsShadow = NO;
wall.geometry.firstMaterial.locksAmbientWithDiffuse = YES;
wall.position = SCNVector3Make(0, 50, -92);
wall.physicsBody = [SCNPhysicsBody staticBody];
[scene.rootNode addChildNode:wall];
}
- (SCNNode *)setupBox:(SCNScene *)scene
{
SCNBox *boxgeo = [[SCNBox alloc] init];
boxgeo.height = 5;
boxgeo.width = 5;
boxgeo.length = 5;
SCNNode *box = [SCNNode nodeWithGeometry:boxgeo];
box.position = SCNVector3Make(0, 0, -30);
boxPosition = box.position;
box.rotation = SCNVector4Make(0, 1, 0, M_PI);
box.physicsBody = [SCNPhysicsBody kinematicBody];
[scene.rootNode addChildNode:box];
return box;
}
- (SCNScene *)setupScene
{
// create a new scene
SCNScene *scene = [SCNScene scene];
//global environment
[self setupEnvironment:scene];
//add elements
[self setupSceneElements:scene];
//setup box
_boxNode = [self setupBox:scene];
[self moveBox];
//create a main camera
_cameraNode = [[SCNNode alloc] init];
_cameraNode.camera = [SCNCamera camera];
_cameraNode.camera.zFar = 500;
_cameraNode.position = SCNVector3Make(0, 60, 50);
_cameraNode.rotation = SCNVector4Make(1, 0, 0, -M_PI_4*0.75);
[scene.rootNode addChildNode:_cameraNode];
return scene;
}
- (void)viewDidLoad
{
[super viewDidLoad];
[[UIApplication sharedApplication] setStatusBarHidden:YES];
SCNView *scnView = (SCNView *) self.view;
scnView.backgroundColor = [SKColor blackColor];
SCNScene *scene = [self setupScene];
scnView.scene = scene;
scnView.scene.physicsWorld.speed = 4.0;
scnView.pointOfView = _cameraNode;
scnView.delegate = self;
[super viewDidLoad];
}
Any ideas why the box node doesn't get stopped by the wall?
Might the problem be that the box node needs to be propelled by a force like the vehicle is in order for the wall to stop it?

Answer 1

What you are trying to accomplish is a little tricky. Moving a box AND making it react to physics interaction is not possible in the way to envision it with a kinematicBody.
You can keep that, but you will need to fake the collision yourself based on position/bounding boxes, or listen for intersections in the Physics World.
You could also change to a dynamic body, that interacts with other dynamics objects. However, in the moveBox function, you are using SCNActions to move the Box. If you are using a dynamicBody, it cannot be moved that way. You'll have to use forces.
The last option is simply to use a SCNConstraint. Not the prettiest, but if your wall doesn't move it will do the trick.