I am very new to Swift and IOS development so this could be a simple question, but I struggle to find the answer on the internet.
I was trying to animate a static DAE model by running a SCNAction on one of its nodes. However, after the SCNAction was completed (and the node was moved), the node position will appear to go back to its original position immediately (same position when the static DAE model was loaded). But when I print the node's position, I noticed that the node's position was actually changed because of the SCNAction. And when I ran the SCNAction again on the same node, the node will go back to the end position resulted from the last SCNAction and start the SCNAction from there. I wonder why there's such mismatch between the node's actual position and the position appeared in the scene.
Another interesting thing was when I put SCNActions in sequence ([action1, action2]), the node will not return to its original position between actions. But if SCNAction.wait was added in between ([action1, SCNAction.wait, action2]), the node will return to its original position during the wait, and will start action2 again from action1's end position.
I am trying to maintain the positions of all nodes at the end of SCNActions. Is there any way to prevent it from going back to the original position?
Not sure if the question is clear enough. Any thoughts and ideas are appreciated.
Have you verified that the node does not come with an animation from the Collada file? Animations and actions are evaluated one after the other. The actions may override the effect of the animation, until they are done (or paused).
Unlike actions, animations don't write in the model tree (node.position) but only in the presentation tree (node.presentationNode.position).
I'm working with SceneKit (swift) and found colorBufferWriteMask parameter that working with SCNMaterial. But it's still working with iOS11+.
So, have anyone know a parameter like colorBufferWriteMask that working with iOS9+?
Thanks.
After research about scenekit, i found a solution. The first, i create a SCNNode (A) that is setting with opacity = 0.000001 and renderingOrder = -1. The second, i create other SCNNode (B) that setting with renderingOrder = 100 and add A.
So, right now, Part of B will be hidden, and this is okie like colorBufferWriteMask.
Thanks.
I have allowsCameraControl property set to true. I need my camera to tell me what it's position and rotation is, while I move it around with pinch and pan gestures so I can later update my camera to that position. Is there some function that is called every rendering moment so I can put println: statement in it? The other option I could think was to set a didSet statement at camera's position and rotation property but I have no idea how to do that if I'm not the one defining the property in the first place.
Found a way around it using custom buttons(moveLeft,moveRight,rotateLeft etc..) to move the camera(and report current position) around 3D space. Works great. Can't tell if mnuages's suggestion works, but it looks allright.
you can use delegation methods such as SCNSceneRendererDelegate's -renderer:didRenderScene:atTime: and you can access the "free" camera by using the view's pointOfView.
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.
So I have a marionette I am making in Sprite Kit, and placing him in a scene. I have created a Marionette class, which is a subclass of SKNode, and when I create an instance of this class, I add a number of SKSpriteNodes to each other. This should give you an idea of how it works (I've snipped out the unnecessary lines):
[self addChild:self.head];
[self.head addChild:self.chest];
[self.chest addChild:self.leftLeg];
[self.chest addChild:self.rightLeg];
[self.leftLeg addChild:self.leftFoot];
[self.rightLeg addChild:self.rightFoot];
So, after doing this, I have my marionette showing up. I want to add a SKPhysicsJointPin to each of these connections. Code looks like this:
self.chestPin = [SKPhysicsJointPin jointWithBodyA:self.marionette.head.physicsBody bodyB:self.marionette.chest.physicsBody anchor:self.marionette.chest.anchorPoint];
At first I thought I could just set up all the pins inside the Marionette class, but that doesn't work (I get EXC_BAD_ACCESS if I recall). It turns out that I have to add the Marionette to the overall SKScene before I add the joints.
This make sense I guess, but I can't help thinking there should be some way I could just set everything up in the Marionette class, and then stick 2 lines of code in the scene to create a new Marionette, then addChild him to the Scene.
As it is, my SKScene subclass has a bunch of code now to add all the pins, and it doesn't feel like it fits in the Scene. Thoughts?
You don't want to use anchorPoint as anchor. The anchorPoint property is a factor which ranges from 0 to 1 and affects how the texture is offset from the sprite's position, ie the default 0.5/0.5 centers the sprite's texture on the sprite's position. In other words anchorPoint is not a position, and using that will anchor the body & head joint to the lower left corner of the screen.
Instead try using either chest or head's position as anchor, or the point in between the two.