I am new to the iOS platform and have written an app using Sprite Kit and Xamarin. To transition between scenes I am using NavigationController.PushViewController with a "Back" button on the new scene to return. This works fine.
My problem occurs when I go back and forth between the original scene and next scene about 3 times. The frame rate (and overall application) slows to a crawl, and depending on which scenes, will hard crash. This happens only on device and not in the simulator. My gut instinct says I'm leaking memory somewhere / not cleaning up properly, so I have just started getting up-to-speed with Instruments. Note that each scene has about 5-8 images on it.
Questions:
What is the proper way to clean-up after transitioning out of a scene back to the previous one? I am explicitly calling RemoveAllActions() and RemoveAllChildren() to ensure clean-up.
What is my best strategy when using Instruments? I've only just begun to experiment with an Allocations trace, but there are a lot of allocations and knowing what to look for is challenging.
Any help is appreciated. I am considering dumping Sprite Kit altogether since my app doesn't really need it (I wanted to experiment) and because it has been a challenge building the app with all kinds of deep crashes (e.g. SKShapeNode, which is very problematic).
Thanks.
Related
I'm working on a SceneKit game using Swift, and I'm thinking about the best way to organize the various screens/ states surrounding the actual main game scene. I have a simple prototype which consists of three states:
Splash Screen (choose game type) ->
Game ->
Game over screen (choose to play again or return to splash)
In the prototype I opted to go for UIKit to do the UI elements, rather than a SpriteKit overlay. Although it's just buttons at the moment, which would be easy enough to do in SpriteKit, I might in future want to add sliders (eg an options screen to set control sensitivity etc), text entry etc, and then you end up recreating great chunks of uikit.
So at present, each of the 3 scenes described above has its own UIViewController. The Splash and Game ViewControllers have their own SCNViews and SCNScenes, and the GameOver is a modal that displays over the main Game scene.
This structure isn't really ideal, as it means that the main game SCNScene gets reloaded whenever the viewDidLoad of the GameViewController fires. The main SCNScene is quite detailed so takes a few seconds to load, and with repeated cycles this seems to create memory issues. After 2 cycles of Splash -> Game -> GameOver I get a memory warning, and after the third cycle Xcode loses the connection to the iPhone (which seems, in my experience, to be caused by memory issues).
I would like to have a main GameViewController that loads the most frequently reused assets once, but still be able to segue between the various menu screens.
So what are the options here?
I thought perhaps I could have a main GameViewController which controls the loading and unloading of SceneKit assets and has the sole SCNView. Its viewDidLoad method would only be fired once, when the app first starts. Then, each of the other views would have a very minimal UIViewController, which would be presented as modals over the main GameViewController, with "OverCurrentContext" selected.
I wanted to ask whether this pattern sounds feasible, and how others organise their SceneKit games. I'm still quite new to native iOS development, so it could be that I'm missing some basic game design pattern.
My Experience with the use of only one GameViewController (my current work for MAC OS X: i started a a 'small' 3D game with a MainMenu/start screen, a Hud and 2 or 3 complete different 3D Scenes - this shall be ported then to IOS, too):
In the last week i tried what you asked for, to use only one GameViewController for "all" that stuff - for me it seemed to be the easy and "good" way to do it - but even after lot of hours with all my tricks I've learned the last years i was not able to reload load another (or change) 3D scene (or even not another sprite kit scene hud) after a scenekit scene is loaded in a single ViewController.
Maybe there is difference between MAC OS X and IOS but i even tried this in an iOS version and it has the same behavior.
What i was able to do: You can modify a loaded 3D scene or change data in the sprite kit hud etc., so you are able to use one 3d scene to add or show the things up when they are needed but as far as my tests here showed, you will need one ViewController to show up a complete new different 3d scene or 2d/3d Menus etc. I will post my further experiences as soon as I'm a step further. i hope this helps a little.
How do you know when to use a loading screen before the game starts? I'm not talking about the splash screen that shows up when you open the app. I'm talking about an actual loading screen (usually with like a loading bar) before the game starts or before the menu options show up? (Examples: Angry birds, Ultimate Briefcase, Clash of Clans) How do you know when you reach the threshold of the number of assets, audio files, etc that need a loading screen? Do you put it in the scene file? or somewhere else?
(This is in context of Xcode / Spritekit)
Sorry for all the questions. Just trying to understand and make my game better. Thanks for the help!
Answer: You shouldn't use a loading screen unless you absolutely have to. Don't use one just for the sake of using one. Use a loading screen if there is a genuine perceivable lag. To determine whether your game lags, benchmark and test your code through the worst scenarios (maximum number of sprites etc.) even if they are unlikely to occur. To understand what constitutes as a lag, the following question will be of great help:
What is the shortest perceivable application response delay?
Where and how you should load your assets is entirely up to you. You should decide that based on many factors, but generally it depends on what happens in your game and how do you handle your resources internally (when do you need resources, when do you release them from memory etc).
I remember that in Apple's Adventure example game (not available for download anymore) all of the shared resources was preloaded at the beginning of the game. Still, you don't have to do that. You can preload your resources when it is appropriate for your app, or maybe you want to release the resources while you are in the menu (or in some other scene than a gameplay scene).
There is nothing written (like in the docs or somewhere else) about when you should show loading screen, or even a rule that you must have a loading screen. The point of a loading screen is better user experience.
Personally, if you have to make a user to wait like 10 seconds before the game starts (which is rare actually), I would do two things there:
1) Show loading image (or something animated, like spinning animation)
2) Show hints or interesting facts about the game, like every 3 seconds (or whatever is an acceptable delay in this situation). This way, you introduce a player with the game while he waits, which is better than let them just wait and look at spinning animation.
I've having an issue with UIWebView and running HTML 5 games (that another developer is working on). We've tried two different options, and neither is optimal.
Option 1: He renders the HTML 5 game with "canvas drawing". When he does it this way, nothing crashes, however in iOS 9 when we go back into the app from the background, the Web View loads back up, but the game is moving much slower than normal (issue not on iOS 7.1 and above). By much slower I'm talking about the animations are not moving the same velocity that they were when we first load the game. The weird thing about this issue is that even if the user opens up a different HTML 5 game (we're adding multiple games) the animations are slower for that game as well. I've tried dismissing the Web View Controller when the UIApplicationWillResignActiveNotification gets posted. When I set the game up this way, the slowness only happens if the app is in the for 4 seconds (it's very strange).
Option 2: He renders the game with "WebGL". When he renders it this way, the app crashes when the app gets backgrounded on iOS 8.0 and above. My research into the crash is that iOS can't draw OpenGL ES in the background. I'm assuming that the WebGL commands are running similar commands as OpenGL ES would do, hence the crash. Dismissing the Web View Controller on UIApplicationWillResignActiveNotification still causes the crash to happen.
Has anyone else ever dealt with a situation like this?
I've not found a good solution to the problem, but I did find a work around.
When I get the App Will Resign Active message, I remove the UIWebView from the UIWebViewController's subview. When I get the Did Become Active message, I add the UIWebView to the UIWebViewController's subview.
This solution works for both cases.
I have a simple scenario (default SpriteKit template): one ViewController and a MyScene SpriteKit scene.
In my ViewController I managed in viewDidLoad the gamecenter initialization but my scene after start immediatelly starts a rather quick sprite movement infinitely (a background parallax scrolling).
Everything works correctly but until GameCenter goes through the authentication procedure my sprite movement lags, breaks, not running fluently.
What practice can I have to minimize this (with keeping the parallax sprite movement running)?
I'm testing this on iPhone4 device (IOS7.03)
GameCenter authentication is actually something that has been causing lag in games for awhile. There are a couple ways people try to get around it, and it's really depends on the app and programmers taste.
Pause the game during GameCenter authentication
This is the easiest way typically, and pretty straightforward.
Put the authentication on another thread
If you desire a fluid option from menu to gameplay, this would be the route to go.
Just use GCD to start a new thread and run the GameCenter authentication in it.
Hope this helps. There might be a couple of other ways, but these are the two I've seen the most. I typically just use the first method.
I'm making a game for iOS where you mostly drag big objects across the screen. When I run the game on an actual iPad/iPhone for a while (continuously dragging the object in circles across the screen) every 5 minutes or so the dragged object goes all stuttery for about 10-30 seconds. Then, it goes back to moving silky-smooth.
Visually, it looks like the game's frame rate dropped to 15 fps for a while, but in actual fact it's running at rock-solid 60 fps all the time. However, I noticed that the only thing that doesn't move smoothly is the dragged object, while the rest of the game is all running perfectly smooth.
This led me to believe that the stuttering is related to the touch input in iOS. So I started looking at touchesMoved, and saw that it's normally called every 16 milliseconds (so touch input runs at 60 fps). So far so good.
Then I noticed that when the object starts stuttering, touchesMoved starts being called at weird time intervals, fluctuating wildly between 8 milliseconds and 50 milliseconds.
So while the touchscreen is in this weird state, sometimes touchesMoved will get called just 8 milliseconds after the previous call, and sometimes it won't get called until 50 ms after the previous call. Of course, this makes the dragged object look all choppy because its position is updated at irregular intervals.
Do you have any idea what could be causing touchesMoved to stop being called at regular intervals, as it normally does?
Bonus:
-Whenever I tilt the screen to force the screen orientation to change, roughly 70% of the time the touchscreen goes into the aforementioned state where touchesMoved starts being called irregularly. Then after 10-20 seconds it goes back to normal and everything looks smooth again.
-I've tried this on two iPads and two iPhones, with iOS 6 and 7, and the issue appears in all of these devices.
-An OpenGLES view is used to display the graphics. It syncs to the display refresh rate using CADisplayLink.
-The Xcode project I'm using to test this has been generated by the unity3d game development tool, but I've found several non-unity games where the same issue appears. this appears to be a system-wide problem. note I'm measuring the timings in objective-c using CFAbsoluteTimeGetCurrent, completely outside unity.
This is not a bug in Unity.
Something inside the OS is getting into a bad state and the touch-drag messages stop flowing smoothly. Sometimes you'll get multiple updates in a frame and sometimes you'll get none.
The issue does not happen on iPhone4 or below, or if the game is running at 30Hz frame rate.
I experienced this bug while using an in-house engine I'd written while working at a previous company. It first manifest itself after upgrading the UI system of a scrabble genre game, where you drag the tiles about on the screen. This was utterly bizarre, and I was never able to pin down the exact reproduction steps, but they seem to be timing related, somehow.
It can also be seen on Angry Birds (unless they've fixed it by now), and a variety of other games on the market, basically anything with touch-drag scrolling or movement. For Angry Birds, just go into a level and start scrolling sideways. Most of the time it'll be silky smooth, but maybe 1 in 10 times, it'll be clunky. Re-start the app and try again.
A workaround is to drop the input update frequency to 30Hz for a few frames. This jolts the internals of the OS somehow and gives it time to straighten itself out, so when you crank it back up to 60Hz, it runs smoothly again.
Do that whenever you detect that the bad state has been entered.
I've also run into this. I can verify that it's a bug in Unity 4.3.x.
My 4.2.x builds process touches on device at 60Hz with TouchPhase.Moved on every frame.
My 4.3.x builds get 20-40Hz with TouchPhase.Stationary being emitted on dropped frames.
TestFlight history saved my sanity here.
Don't forget to file a bug with UT.
It's a real disaster. Sometimes it's lag and sometimes it's really smooth. It lags even when GPU and CPU utilization are below 10%. it's not Unity bug. I'm using cocos2d v3.
If someone found a cure, please post it!
I've been running into this as well. My current hypothesis which I still have to verify is that if you ask for a given frame rate (eg. 60fps), but your actually achieved frame rate is less than that (eg. 45fps) that this causes a timing/race condition issue between Unity requesting inputs from iOS at a higher frame rate than it actually is running at. However, if you set it to 30fps (at least in my UNity 5.2 tests with iOS 9.1) then you get a solid 30Hz of input. When I disabled a chunk of my game and it was running at a very solid 60fps, then I would consistently get 60Hz of input from the touch screen. This is what I have for now, but I have to prove this in a simple project which I haven't had time to do yet. Hope this helps someone else.
I found a potential solution to this problem here: https://forums.developer.apple.com/thread/62315 (posting here because it took me a lot of research to stumble across that link whereas this StackOverflow question was the first Google result).
To follow up on this, I got a resonse on my bug report to Apple. This
is the response:
"As long as you don't cause any display updates the screen stays in
low power and therefore 30hz mode, which in turn also keeps the event
input stream down at 30 hz. A workaround is to actually cause a
display update on each received move, even if it is just a one pixel
move of a view if input is needed while no explicit screen update will
be triggered."
In my application, using a GLKView, I set its
preferredFramesPerSecond to 60. Occasionally, my input rate would
randomly drop to 30hz. The response from Apple doesn't fully explain
why this would happen, but apparently the expected method of handling
this is to call display() directly from touchesMoved() while dragging.
I've subclassed GLKView and I set preferredFramesPerSecond to 60. On
touchesBegan(), I set isPaused=true, and start calling display()
within touchesMoved(). On touchesEnd(), I set isPaused=false. Doing
this, I'm no longer having any issues - the app is more performant
than it's ever been.
Apple's example TouchCanvas.xcodeproj does all drawing from within
touchesMoved() as well, so I guess this is the intended way to handle
this.
As far as I can tell, your best bet to achieve a smooth look may be to interpolate between touch events, rather than immediately mapping your objects to your touch position.
tl;dr: It seems just having a CADisplayLink causing any OpenGL context or Metal device to draw at 60fps can cause this.
I was repro'ing this on my iPhone 7 Plus w/ iOS 10.2.1.
I made a small sample simple app with a CADisplayLink with preferredFramesPerSecond = 60, and tried the following rendering approaches:
GLKView w/ display()
CAEAGLLayer, used as prescribed by Apple at WWDC (opaque, sole layer, fullscreen, nothing drawn above it)
MTLDevice
In each case, the render method would only clear the screen, not try drawing anything else.
In each case, I saw the input rate problem.
The following "tricks" also seemed to do nothing, when called inside touchesMoved:
Calling glkView.setNeedsDisplay() (with enableSetNeedsDisplay set to true)
Moving some other view
Calling glkView.display() (actually, seems like it can raise your input rate to 40 events per second. But it doesn't look any better, as far as I can tell, and seems wrong to do, so I wouldn't recommend it.)
I gave up, after running all these tests. Instead, I interpolate my object between the touch positions instead. So it's what I'd recommend, too.
But I figured I'd include my research here in case somebody else takes a stab at it and finds a better solution.