Have a quick question to see if I'm using isNode(_:insideFrustumOf:) correctly.
I'm putting an node (SCNNode) into an ARSCNView with standard configuration. The geometry in the node is off-centered so I used the node's pivot property to adjust its center point.
let c = object.boundingSphere.center
object.pivot = SCNMatrix4MakeTranslation(c.x, c.y, c.z)
object.position = c
My issue arises after I update the object's scale or rotation using a pinch gesture. After this happens, I get different results from isNode(_:insideFrustumOf:) and from nodesInsideFrustum(of:).
The node I'm testing is clearly visible in the screen, but isNode(_:insideFrustumOf:) fails to see it. However, the node is in the [SCNNode] results from nodesInsideFrustum(of:).
My question is whether this is a bug, or is there some other proper way of centering geometry to a node that may fix this issue. For now, I'm going to use the nodesInsideFrustum(of:) function and test if the object is in the array.
Thanks!
The trick is making sure you are using the ”presentation” node for any moving objects, even the pointOfView if it’s moving.
This is a working snippet from my app inside the renderer: (updateAtTime)
if renderer.isNode(stationaryObjectNode, insideFrustrumOf: renderer.pointOfView!.presentation) == true {
//do stuff if seen
}
If your object is not stationary, use movingObject.presentation instead of stationaryObjectNode
Related
I am trying to figure out a way to have a property called isJumping on a SCNNode subclass. The property is set to true whenever the nodes jump() function is called and the jump is implemented using .applyForce(x: 0, y: jumpForce, z: 0, asImpulse: true). However, there is no way (that I can figure out) that allows the node to set the isJumping property back to false. My thinking is that if there was a way to tell if the node was touching the ground or not, then this would be an ideal solution. Does anyone have any ideas on how this isJumping property could be implemented? Or perhaps a way to compute the isJumping property using physics?
Things I've tried:
Checking vertical velocity != 0
This doesn't work because at the peak of the jump the vertical velocity is 0. In addition, when the node is rotated to "stand up" and "lie down" using SCNActions, even though the pivot point is the nodes "foot" and never really leaves the floor, it is still considered to have a vertical velocity and thus is incorrectly labelled as in a jumping state.
Checking position
This is unreliable because if the node were to hypothetically jump onto a platform, the node would be considered in a jumping state.
Something that may work:
Applying a downward force on the physics body and check in the next frame if the y-position changed at all. If it didn't change that means it rebounded off of something and in that instance I can change the isJumping property to false. Keep in mind, ideally, I wan't to be able to do this without leaving the subclass (however, using helper classes is completely fine).
I built a complete structure as a node (with its child nodes) and the user will walk through it using ARKit.
At some point, if the user cannot continue because of some real obstacle in the real world, I added a "pause" button which should freeze whatever the user currently sees in front of the camera, the user could then move freely to some other open space and when the user will release the pause button he/she will be able to resume where they left off (only someplace else in the real world).
A while ago I asked about it in the Apple Developer forum and an Apple Frameworks Engineer gave the following reply:
For "freezing" the scene, you could transform the anchor's position (in world coordinates) to camera coordinates, and then anchor your content to the camera. This will give you the effect that the scene is "frozen", i.e., does not move relative to the camera.
I'm currently not using an anchor because I don't necessarily need to find a flat surface. Rather, my node is placed at a certain position relative to where we start at (0,0,0).
My question is how do I exactly do what the Apple engineer told me to do?
I have the following code which I'm still stuck with. When I add the node to the camera (pointOfView, last line of the code below), it does freeze in place, but I can't get it to freeze in the same position and orientation as it was before it was frozen.
#IBAction func pauseButtonClicked(_ sender: UIButton) {
let currentPosition = sceneView.pointOfView?.position
let currentEulerAngles = sceneView.pointOfView?.eulerAngles
var internalNodeTraversal = lastNodeRootPosition - currentPosition! // for now, lastNodeRootPosition is (0,0,0)
internalNodeTraversal.y = lastNodeRootPosition.y + 20 // just so it’s positioned a little higher in front of the camera
myNode?.removeFromParentNode() // remove the node from the Real World view. Looks like this line has no effect and just adding the node as a child to the camera (pointOfView) is enough, but it feels more right to do this anyway.
myNode?.position = internalNodeTraversal // the whole node is moved respectively in the opposite direction from the root to where I’m standing to reposition the camera in my current position inside the node
// myNode?.eulerAngles = (currentEulerAngles! * -1) — this code put the whole node in weird positions so I removed it
myNode?.eulerAngles.y = currentEulerAngles!.y * -1 // opposite orientation of the node so the camera will be oriented in the same direction
myNode?.eulerAngles.x = 0.3 // just tilting it up a little bit to have a better view, more similar to the view as before it was locked to the camera
// I don’t think I need to change the eulerAngles.z
myNode!.convertPosition(internalNodeTraversal, to: sceneView.pointOfView) // I’m not sure I wrote this correctly. Also, this line doesn’t seem tp change anything
sceneView.pointOfView?.addChildNode(myNode!) // attaching the node to the camera so it will remain stuck while the user moves around until the button is released
}
So I first calculate where in the node I'm currently standing and then I change the position of the node in the opposite direction so that the camera will now be in that position. That seems to be correct.
Now I need to change the orientation of the node so that it will point in the right direction and here things get funky. I've been trying so many things for days now.
I use the eulerAngles for the orientation. If I set the whole vector multiplied by -1, it would show weird orientations. I ended up only using the eulerAngles.y which is the left/right orientation and I hardcoded the x orientation (up/down).
Ultimately what I have in the code above is the closest that I was able to get. If I'm pointing straight, the freeze will be correct. If I turn just a little bit, the freeze will be pretty close as well. Almost the same as what the user saw before the freeze. But the more I turn, the more the frozen image is off and more slanted. At some point (say I turn 50 or 60 degrees to the side) the whole node is off the camera and cannot be seen.
Somehow I have a feeling that there must be an easier and more correct way to achieve the above.
The Apple engineer wrote to "transform the anchor's position (in world coordinates) to camera coordinates". For that reason I added the "convertPosition" function in my code, but a) I'm not sure I used it correctly and b) it doesn't seem to change anything in my code if I have that line or not.
What am I doing wrong?
Any help would be very much appreciated.
Thanks!
I found the solution!
Actually, the problem I had was not even described as I didn't think it was relevant. I built the AR nodes 2 meters in front of the origin (-2 for the z-coordinate) while the center of my node was still at the origin. So when I changed the rotation or eulerAngles, it rotated around the origin so my nodes moved in a large curve and in fact also changed their position as a result.
The solution was to use a simdPivot. Instead of changing the position and rotation of the node itself, I created a translation matrix and a rotation matrix which was at the point of the camera (where the user is standing) and I then multiplied both matrices. Now when I added the node as a child of the camera (pointOfView) this would freeze the image and in effect show exactly what the user was seeing before it was frozen as the position is the same and the rotation is exactly around the user's standing position.
All,
There is a specific switch to make normals, geometries and other parts of all nodes in a scene visible.
I thought I kept it somewhere in my code, but I must have erased it somehow.
I need this function because the contact detection doesn‘t seem to work right.
I want to detect if thrown grenades in a tunnel touch the tunnel walls. Right now, most of them just fall through.
Anybody know the command?
Like showBoundingBoxes?
SCNDebugOptions
Edit:
You can put it UIViewController along with...
gameScene.allowsCameraControl = false
gameScene.showsStatistics = false
Go to this link and see SCNDebugOption for a complete list.
https://developer.apple.com/documentation/scenekit/scnscenerenderer/1523281-debugoptions
I'm new to ARKit and SceneKit. I have a rather complex scene coming from an 3D artist. He replaced some items with SceneKit objects. I now try to change the properties of one of the SCNNodes, in this case the scale property, in another case the position in space, and in yet another I have a SCNText where I change the string property:
feedScaler?.scale = SCNVector3Make(1.0, scale, 1.0)
feedText?.string = String(feedValue)
feedIndicator?.position.y = someNewValue
So, pretty straight forward. When I run the scene though, it seems that the changes here are only commited once, before the scene appears. Then nothing happens. Here's the thing:
the method which updates the properties runs once per frame
I print out the property values of the nodes to the console and they update each frame
the text updates, too, and is the only update which is actually rendered and visible.
Note: There's also animations in that scene that do not play unless I uncheck "Use scene time base". Maybe that is a hint regarding how the Scene's animations are handled...
I found the issue. I used a clone of the scene which caused the references to get lost. The documentation says:
Cloning or copying a node creates a duplicate of the node object, but not the geometries, lights, cameras, and other SceneKit objects attached to it—instead, each copied node shares references to these objects.
When the original gets lost all the references get useless.
I can't change the position of a SKSpriteNode by changing
self.position = newPosition;
It doesn't work anymore if it has a physicsBody.
A workaround I got is:
self.myStar.physicsBody = nil;
[self.myStar changePosition];
self.myStar.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:self.myStar.size.width/2];
Or
[self runAction:[SKAction moveTo:newPosiion duration:0.0]];
But #2 isn't smooth. It needs to pop up on another position without a moving action.
I had the same problem. Apparently you cannot explicitly set the position of a Sprite node once it has a PhysicsBody. I solved it by temporarily removing the sprite node's PhysicsBody.
CGFloat yPosition = 400.f;
SKPhysicsBody* goldfishPhysicsBody = _goldfish.physicsBody;
_goldfish.physicsBody = nil;
_goldfish.position = CGPointMake(_goldfish.position.x, yPosition);
_goldfish.physicsBody = goldfishPhysicsBody;
Yes, you can!
I'm not sure what exactly you're doing and where exactly you run this code and what the observed effect is that you meant by "can't change position" but changing a node's position always works, whether the node has a physicsBody or not, and whether the physicsBody is dynamic or static. I verified this in a simple test project with dynamic set to both YES and NO, with both circle and edge loop body types, using both position property and move actions.
You can change the node's position either by setting the position property directly or by using a move action - both variants work. If you use a 0 duration for the move action, it effectively becomes the same as setting the position property.
So whatever problem you're observing, it's not because you can't generally change a node's position once it has a physicsBody. That's absolutely not the case.
I'm guessing you may have run into one of the following problems:
node is already running a different move action, overriding your position changes
you were looking at the wrong node (use logs to verify actual position of the node in question)
you change position elsewhere, for example setting the node's position every frame thus invalidating any other position change
if it's not one of the above, then possibly something else I couldn't think of ...
I had a problem like this where I tried to update position inside didBeginContact:, but it was not having any effect, I think because the physics simulation immediately clobbers the value.
My solution was to cache the new position in a property on my scene and then update the position of the node next time update: was called on my scene.
[SKAction moveTo:newPosition duration:0.0] worked for me, too, and there was no popping. I haven't decided yet which is more elegant.
I think the problem you are having is that in order for you to control a phsyics body, you need to set it to dynamic.
self.myStar.physicsBody.dynamic = NO;
If the dynamic property is set to YES, then the physics engine is in control of it's movement.
As noted in the comments, setting dynamic to NO shouldn't restrict movement via SKAction or position property. However, if it is set to YES, it's possible that something in the physics engine is affecting your attempt to move the node.
If you want the movement to not pop, then you need to set a duration higher than zero to your SKAction or it will pop as you have described. Setting duration to 0.0 is the same as just changing the position.
For example :
[self runAction:[SKAction moveTo:newPosition duration:1.0]];
will move the node to the new position over 1 second.
I ran into a similar problem. When using SKAction, even with duration set to 0.0 I got strange behaviours especially when two SKActions had been triggered at the same time.
I tried setting position directly but as mentioned by others this doesn't work when using the SKPhysicsContactDelegate.
However for me it worked to remove the node from its parent, I then set the new position, and other things I want to change, and then I add the node again to its former parent.
It's not ideal but in some cases it might help.
As an example with the SKPhysicsContactDelegate method didBegin:
func didBegin(_ contact: SKPhysicsContact) {
guard let node = contact.bodyB.node else { return }
node.removeFromParent()
node.position = CGPoint(x: 10, y: 10)
addChild(node)
}
Seems similar to SKSPriteNode position changes to 0,0 for no reason
As stated in answer and comments of this question, it seems you must either set the position before setting the physicsBody and/or set the physicsBody after adding the node to your scene.
I've had this problem in several scenarios and I haven't found out what exactly causes it to fail sometimes.
Yes you can, but it has its price.
I think you have to make a decision: Either let the position being calculated by the PhysicsEngine OR set the position on your behalf.
Look, for an object in a physics world, there is no magical movement from 'outside', there is only forces, collisions, drifts, ... and that will lead to any position. You can not manipulate the position without putting forces on some related nodes.
And in the moment you try BOTH, having a physicsBody (e.g. on your player), but also try to move them around by setting position manually or running actions for moving, YOU LEAVE the world of physics. Your player will be MOVED through walls and so on, against all physics rules.
So, to want an object being manipulated by the physics engine on the one hand and also to want "positioning" by code is kind a contradiction.
There are - of course ways - to combine both ways (e.g. the mentioned 'workaround' by temporarily removing the physicsBody), but this has also its price and has to be sequentially. You can not have both ways at the very same time.