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.
Related
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 have a game with a character that can cast fire balls. Right now in my game, when I tap anywhere on the screen, I shoot a fireball at my touch point. For this fireball I'm using an SKEmitterNode where I've created a fireball particle emitter.
The problem I'm running into is, my fireball has an angle set already, but I want that angle to change based on where I tap, so that the trailing flames are behind the fireball, not going up or down or whatever I've set it to in the sks file.
I've never done something like this, is there something built into swift already for calculating angles? I can't find much on google
There are two options:
1) first one is that you can use :
fireBall.moveTo(touchLocation.x, touchLocation.y)
function so you can avoid use angles (if I understand you correctly). touchLocation is CGPoint of location of the touch event.
2) second one use as it was said before you will get an angle:
atan2(deltaY,deltaX)
I have working implementation of drag and drop feature written in Cocos2d + Box2d for iOS. I need to port it to Sprite Kit. The logic is pretty basic:
when user touching the screen, find sprite under the finger
create mouse joint between found sprite and the scene's physics body, set joint's target to position of touch
when touches moved, update joint's target to new position
when touches ended, remove the joint
Everything is working quite well. I like the way physics is simulated when touches ends - the dragged shape has velocity dependent on dragging speed and direction, so when I left my finger from the screen while moving the sprite, it will continue moving in the same direction, but now affected by gravity and damping.
Unfortunately, I'm not able to reproduce the same effect using Sprite Kit. There is no such joint like mouse joint, but I have tried using other joint types. I almost succeeded with SKPhysicsJointFixed - I'm creating new sprite and joint between it and dragged sprite, when touches moving I'm moving the newly created sprite. Unfortunately it doesn't work like mouse joint in Cocos2d + Box2d - while dragging the sprite, its velocity always equals zero. So, every time I left my finger from the screen, the dragged sprite stops immediately and start falling affected by gravity. No matter how fast I move the finger when dragging, after releasing dragged shape, it behaves exactly the same way.
My question is how to implement mouse joint in Sprite Kit, or how to implement drag and drop feature that works like described above?
Update:
This is a box2d mouse joint example that could give you more clear view on what I am trying to implement using Sprite Kit:
http://blog.allanbishop.com/wp-content/uploads/2010/09/Box2DJointTutorial1.swf
I'm pretty new to iOS development so I guess this might not be the best way, but this is how I solved it and it seems to work pretty smooth actually.
I'm using a UIPanGestureRecognizer to handle the touch event. I set this one up in my didMoveToView: with this code:
UIPanGestureRecognizer *gestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handlePan:)];
An UIPanGestureRecognizer is passed to handlePan: and I check with recognizer.state == UIGestureRecognizerStateEnded if the touched stopped. This is where I want to "release" the object and "let it fly away". For doing so I needed to calculate a few things, first of all I get the velocity of the finger/touch with this code:
CGPoint velocity = [recognizer velocityInView:recognizer.view];
(I use the same method (handlePan:) with other statements for getting the right object when touch starts, and letting the object be under the finger all the time by setting the position of the object to the location of the touch when moving)
Now I know the velocity, but I still don't know how much force I need to apply to the object. You should be able to calculate the force by this formula: Force = mass * acceleration. We know the mass (object.physicsBody.mass) and we know the velocity. To get the acceleration we need the time as well because acceleration = velocity / time.
In my update: method that is called every time a new frame is to be rendered I calculate the difference between the last time a frame was about to be rendered by doing something like this:
self.delta = currentTime - self.lastTime;
self.lastTime = currentTime;
I now can calculate which force that is needed to get the object moving in the velocity I'm "dragging it in". To do this I do the following:
[self.currentNode.physicsBody applyForce:CGVectorMake(velocity.x/self.delta * self.currentNode.physicsBody.mass, -velocity.y/self.delta * self.currentNode.physicsBody.mass)];
I take velocity divided with the difference in time since last frame (self.delta) to get the acceleration, and then multiply it with the mass of the object to get the force needed to keep (or actually getting) the object moving in the same direction and in the same velocity as it was moved by my finger.
This is working for me at the moment and I hope it helps other people too, and please tell me if I got something wrong or if there is a better solution. So far I have not found any "native solution".
If the only issue is velocity, then that is simple to fix.
Subtract the current touch position from the previous touch position to get the velocity between the last and current touch. Use applyForce: to apply this velocity to the body.
In order to prevent the body from moving on its own while dragging, read out the new velocity from the body after calling applyForce: and keep it in an ivar and set the body's velocity to zero.
When the touch ends, set the body's velocity to the one you keep as an ivar.
If this doesn't work, try using applyImpulse: and/or setting the velocity before calling any of the two methods, ie:
sprite.physicsBody.velocity = bodyVelocity;
[sprite.physicsBody applyForce:touchVelocity];
bodyVelocity = sprite.physicsBody.velocity;
sprite.physicsBody.velocity = CGVectorMake(0, 0);
That way you can keep the body's velocity without losing control over it while dragging.
I have a question about cocos2d and box2d.
I have to create a simple wheel that rotate according how the user touch the wheel for an Ipad App.
I would like that according a certain touch movements the wheel start with a certain velocity, and after some rotation start to decrease velocity until it stops. (like a classic lucky wheel).
I need some hint. Do you think that is possible to do that using only cocos2d? Or I have to use Box2D? I already started to use Box2d, it's very powerful, but is it possible to give an object a certain starting velocity rotation and after, let the world simulation to stop the object?
Thanks a lot!
Benza
When i developed the exact same thing on Android i also couldn't find any useful examples/articles to implement this, so i did it like this:
When a user touches the screen and does a fling/swipe (moves his finger across the screen and removes it from the screen) you calculate the speedX and speedY in pixels/second (in android you have a method onFling(float velocitY,float velocitX)).
You then convert the speed which is in pixels/second to revolutions/second. This means that if the users fingered would traveled 1500 px in 1 second, your wheel would spin X times. For example if the fling/swipe speedX and speedY is 1500 px/s and your wheel has a radius of 150px, you calculate the wheel arc length like so:
arc = r * PI. (r=150)
Then you calculate the speed in revolutions per second like this:
spinSpeed = Math.sqrt((speedX*speedX)+(speedY*speedY))/arc)*360
Once you have the speed you can change the wheel rotation angle every T miliseconds (i used 40miliseconds) like this:
wheel.angle += spinSpeed;
You also have to implement drag, so the wheel eventually slows down, like this:
spinSpeed -= drag_value;
wheel.angle += spinSpeed;
You have to adjust the drag_value to your desired effect (how fast it slows down). You may also want to multiply the spinSpeed by a constant, so you get higher speed (i used 40).
This implementation doesn't include the wheel following the users finger. To do that you have to calculate for how much the users finger moved since the last touch of the screen (for X and Y coordinates). So you need 2 coordinates (lastTouchX,lastTouchY,newTouchX,newTouchY). When you have the coordinates you can calculate the slope or gradient of the lines that go through this coordinates (the slope/gradient is K in this formula: y = kx +n - standard line formula). Then you have to calculate the intersection angle between this two lines and apply it to the wheel. Something like this:
tg = ((k1-k2)/(1+(k1*k2))); // k1 is the slope of the previous touch coordinate; k2 is the slope of the current touch coordinates
angle = Math.toDegrees(Math.atan(Math.abs(tg)));
wheel.angle += angle; // to implement spinning in the other way use wheel.angle -= angle;
Hope you get the idea
u might have figured it by now but any ways .. u can create the wheel and start with some initial rotation and velocity on touch. then have friction enable according to your need that would show down the object after some time .
Hope it helps