I've been fiddling with SceneKit recently and I wanted to make the following thing:
When creating a Game template from Xcode, you get a scene with a ship.
I wanted to animate this ship and orient it according to the relative position of my iPhone after I tap the screen. So for instance, if I hold my iPhone horizontally, tap the screen, this takes the reference attitude of my horizontal iPhone. Then, when I lift it (changing the pitch), I want the ship to orient itself as such.
I've been trying to change my ship node eulerAngles with the attitude pitch yaw and roll as in the following:
CMAttitude * attitude = deviceMotion.attitude
_ship.eulerAngles = SCNVector3Make(-attitude.pitch, attitude.yaw, attitude.roll);
Whenever I do that, the ship goes back to its original position in the scene. I can't seem to understand how to give it a speed in the direction it's facing without making it reset to its original position when I change its eulerAngles.
Ideally, the ship would have some sort of engine power accelerating it in the direction it's facing, while it would still be affected by gravity. How should I do that? Thanks!
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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.
I have been trying to achieve the animation in this link: http://www.visa.com/rio2016/na-en/#!gallery on an iPad. Try opening this link on and iPad and you'll see.
Basically, its a wrapped(360 degree/Infinite) horizontal list. If the user moves in circle the list on the device should follow the movement.
I know that JS uses webkitCompassHeading to calculate the compass readings.
I tried using the accelerometer but the issue is the deceleration factor is quite small. Lets say I am am moving in right circular motion, list scrolls backwards or from right to left, everything is fine. I stop and start moving in reverse, the deceleration is there but for a very short time. So for the reverse movement, only 1 or 2 carousel items gets scrolled forward or left to right and again since the accelerometer picked the +ve acceleration, the list starts moving in backwards or from right to left direction.
Tried it with magnetometer, by storing the last angle of rotation and seeing if the new one has changed by 6 or 7 degrees but the values are too shaky.
I'm trying to figure out a method for rotating a SKSpriteNode object while it is in-flight (being affected by gravity) along an arc path. I'm using SpriteKit and throw the object using applyImpulse. The problem is that the object, despite traveling in an arc path in the air, stays in the same position.
Imagine an archer shooting an arrow. The arrow is shot upwards and should point upwards in that direction. Once the arrow starts falling along the arc, it should begin to rotate downwards.
Is there some way to automate this using the SpriteKit physics? Should I throw the arrow a different way instead of using applyImpulse? Do I need to come up with some algorithm by myself for the rotation based on the objects velocity?
In your didSimulatePhysics or your update you can rotate your sprite towards its vector. Not sure theres a way to automatically make this happen.
let angle = atan2(mySprite.physicsBody!.velocity.dy, mySprite.physicsBody!.velocity.dx)
mySprite.zRotation = angle
What I'm attempting to recreate is the draggable arrow that's used in the popular iOS game called "Fragger", complete with both adjusting the rotation AND the strength of the pull all at the same time based on a finger drag but using SpriteKit - I believe they did it in Cocos2D.
I'll start by saying that I've honestly spent many weeks relearning trigonometry (http://www.mathsisfun.com/ is a great resource) and combing through Ray Wenderlich's tutorials (http://www.raywenderlich.com/35866/trigonometry-for-game-programming-part-1) but I can't find a solution for executing a "collective" drag rotation AND strength on a SpriteKit object.
Yes, it's relatively easy to set an anchor point and rotate that object (I'm using an arrow) so that it's pointing at your finger and thanks to Ray, I've got a really smooth action utilizing the following:
float angleRadians = atan2f(firstFingerTouchY - _arrow.position.y, firstFingerTouchX - _arrow.position.x);
float angleDegrees = RADIANS_TO_DEGREES(angleRadians);
float rotateDegreesPerSecond = 180 / 0.5; // Would take 0.5 seconds to rotate 180 degrees, or half a circle
float degreesDiff = (angleCurrent - angleDegrees) * 1.0;
float rotateDuration = fabs(degreesDiff / rotateDegreesPerSecond);
however, that's only part of the equation ...
Again, the first drag is fine as the angle of rotation is derived from the fulcrum of the arrow (it's anchor point) and where ever my finger ends up. However, let's say due to the limit of the screen size I can't get the angle I desire in a single drag, so I lift up my finger and then place it back down to continue the drag? Well I can't use the above mentioned code because as soon as I place my finger down for the second time, the arrow's rotation jumps over to where my finger now starts - again ending the same way.
So I thought the solution would be to not use the anchor point of the arrow at all, but instead use the initial finger touchpoint (as the new anchor) and calculate the arrow's angle based on that touchpoint and where ever my finger moves to? That works in theory, however when you then try to factor in the "strength draw" aspect that's represented in "Fragger" (where pulling the finger closer or farther away from the arrow adjusts the strength of the grenade throw), then you're not moving your finger towards the arrow to weaken the pull, but instead towards where ever you initially touched - which is not only visually difficult but as a bonus creates a lot of rotational jerky-ness as you get your finger closer to the origin.
I've been working on it for about a month now (did I mention that I hate math) trying to create a homogenized method (SIN ... COS ... TAN ... I hate you all!) to do the following:
First pull will rotate the arrow based on the direction of the pull but NOT automatically point to your finger (initial angle)
The ability to lift my finger up, place it back down and drag to ADD TO or SUBTRACT FROM the current rotation of the arrow. (delta angle)
The drag of my finger towards or away from the anchor of the arrow (relative to the current angle of the arrow) will adjust the strength of the "pull" accordingly. For example, if the arrow is already pointing straight up, then continuing the drag straight up would increase the strength and down would decrease the strength respectively. (hypotenuse derived from arrow anchor point).
I also need to be able to use another finger (2 finger touch) to assist in the rotation/strength calculation, so that adds even more chaos into my cluster ...
If you've ever played the 'Fragger' game, you'll recognize the complexity of this single finger action which is also it's functional beauty. I can get pieces of it working - I can rotate it, I can adjust a color mask to indicate strength - but not all of it working together. Perhaps I'm going about it completely wrong, however every example I find online stops at simply rotating an object to point to your finger with every new touch drag ending with the same results.
I have a SpriteKit Scene in which I want to have the effect as if a camera zoom and scale. Does anyone know of any libraries or some easy methods of doing this?
It was very easy to do in other 2D engines but does not seem simple.
I was thinking of doing it from the app delegate, and using the window to zoom since my character does stay around the same position.
The desired effect I would like to accomplish is like that of the start of an Angry Bird level when the camera pans into the level and then the launch doc.
http://www.youtube.com/watch?v=_iQbZ3KNGWQ This is an example of the camera zoom and pans I am talking about.
Thanks for the help.
If you add an SKNode to the SKScene, and make your scene content children of that node instead of direct children of the scene, then you can zoom and pan all of the contained content just by adjusting the xScale, yScale and position properties of the added node. (Any content you did not want scrolled e.g. scores or whatever could then be added to a different SKNode or added directly to the scene).
The adjustment could be done by overriding one of update:, didEvaluateActions, or didSimulatePhysics in your SKScene subclass. The choice would depend on if you are just moving your character around by yourself in update:, or if it also gets moved around by running SKActions or by simulated physics.