I am making a drawing on NSView using a timer that is set to update every .02 seconds. On update some physical simulation makes a step, and then Canvas!.needsDisplay = true. It works when app is in foreground (usually), but when some lags happen, simulation progresses forward despite the fact that view hasn't reflected it yet. How do I pause the timer during these times to make simulation happen only when NSView can show it? I do not want to call step_over from inside drawRect, cause it seems like a bad idea, because then it would be harder to stop the simulation.
Generally this kind of update should be done the other way around, by letting the display ask you for frames as it can display them. This is done with a CADisplayLink CVDisplayLink (this is Mac; CADisplayLink is iOS). Configure it with a method you want to be called when a frame can be drawn.
Generally you do want your simulation to keep moving forward, even if it means dropping frames occasionally. For that, you check the timestamp and use that to work out what time to use for your new frame. But if you only want to move forward when the display can show it, then just update once per call.
Note that generating at 50fps is often going to mismatch the system that's trying to draw at 60fps, so you're going to wind up missing frames occasionally. That's one of several reasons not to try to push drawing with a timer.
See also Alternative of CADisplayLink for Mac OS X. Note that trying to draw at 50fps with Core Graphics usually isn't going to give good results in any case. The right tool here in OS X is Core Animation (or SpriteKit for games on 10.10, or OpenGL for more advanced high-speed rendering). You can do very basic animations with an NSTimer (and we did for years before Core Animation came along), but it's not really a tool for complex drawing.
Related
I am developing an aframe project on my MacBook pro, late 2013. When running the project, the fan of my computer always spins fast, regardless which browser I use (firefox, safari, chrome) and the project size (also happens with a project just containing a simple a-box).
aframe-stats show me that my project (1028244 vertices, 342748 faces) still runs with 20 fps.
Is it somehow possible to limit the frame rate to 10fps in order to keep my computer quite? Or any other way to limit the flop-consumption of the aframe project? I already tried a native approach with sudo cputhrottle plugin-container 10 but that did not just throttle the aframe-renderer but the whole firefox browser. Can I pull the break somewhere in the JavaScript or the Browser settings?
It's difficult to say without your project code. Large data sets will simply crank out even a high spec macbook pro. I have found it helpful to pause any rendering whenever possible to quiet the users' machines.
I personally removed automated next animation frame rendering in favor of waiting for controls and objects to change.
For example:
this.controls.addEventListener( 'change', function(e){ addToRenderStack(); });
A simple function addtorenderstack puts in a new value in a list for a render, with the expectation that the render will occur at some point in the future and not right away. the list can also be used to log who requested the render in the call stack, and narrow down performance hogs.
addtorenderstack places a render request in a list. In the requestanimationframe loop, if the list has any length, a render is called on the scene. The stack is immediately cleared rather than processed one by one. If controls or animations continue to make render requests, the list will have a length again and request animationframe will process them in the same way with another render.
In this way, the code only renders when absolutely required. This saved me much grinding on framerate and the fans only come on during intensive operations and then shutdown when its complete, much like a typical 3d game experience.
Your mileage may vary depending on what's happening in your app. I work in engineering so often the view of the 3d world is stopped as an engineer examines or shows a model.
I am trying to create an application with an OpenGL view using MonoMac. Setting up an application and an NSOpenGLView was fairly simple...
...but for some reason I cannot get a consistent frame rate rendering OpenGL. The issue I am having is that 9 out of ten frames have perfect performance and every tenth frame or so I am getting a massive frame time spike (about 60ms-80ms for a single frame). The time of the slow frame correlates with the size of the control (and even more so using retina backing buffer).
I have been digging and have come up with nothing that works for my case.
I tried to use NSOpenGLView with CVDisplayLink and rendering on the main thread with timers and DrawRect.
I tried MonoMacGameView also both versions. Actually MonoMacGameView has consistent performance but only draws when my window does not have a background color.
I reimplemented the run loop to do my own NextEvent polling just to find out that that is not the issue...
So, my current hunch is that it has something to do with layer backed rendering in Cocoa views but I really cannot figure out what is causing this.
Any hint as to what is causing this delay?
I found a solution which produces pretty good results:
Do not use NSOpenGLView or MonoMacGameView.
Use the approach described in the example on this page: http://cocoa-mono.org/archives/366/monomac-and-opengl/
To enable retina support export the ContentScale property on the deriving class and set that depending whether you are running on retina screen or not
In conclusion, using a core animation layer is the only viable solution.
I have a custom UISlider and use the currentPlaybackTime to change values of an MPMoviePlayerController object.
The problem is when i scrub at a fast rate using the slider, it doesn't respond as fast as i would like..
Is there any better way to have a fast interactive scrubber for ipad? targeting from OS 3.2
Well there are two issues, only one you can control directly.
Multimedia-content is commonly compressed using some kind of delta-compression, hence quick and exact seeking is not a trivial task to cope with. As that is common and since you can not directly change that, you will have to live with it.
the only way to increase responsiveness for seeking on the content-side (when encoding) is reducing the gop-size - that is, less p-frames between the i-frames.
when using a slider or a similar control, you could, instead of directly connecting the current playback position with it, handle any manual changes in an indirect fashion. You could run a timer based job that, whenever the slider/scrubber has been moved, tries to adjust the playback position towards that new value. Once the player is seeking, prevent the scrubber from getting feedback from the current playback location but allow it once the player is in playing state again. That way the user does not directly experience the clunky seek feedback.
I've been having problems and, after spending a week trying out all kinds of solutions and tearing my hair out, I've come here to see whether anybody could help me.
I'm working on a 3D browser plugin for the Mac (I have one that works on Windows). The only fully-hardware accelerated way to do this is to use a CAOpenGLLayer (or something that inherits from that). If a NSWindow is created and you attach the layer to that window's NSView then everything works correctly. But, for some reason, I can only get a specific number of frames (16) to render when passing the layer into the browser.
Cocoa calls my layer's drawInCGLContext for the first 16 frames. Then, for some unknown reason, it stops calling it. 16 seems like a very specific - and programmatic - number of frames and so I wondered whether anybody had any insight into why drawInCGLContext would not be called after 16 frames?
I'm reasonably sure it's not because I pass the layer into the browser - I've created a very minimal example plugin that renders a rotating quad using CAOpenGLLayer and that actually works. But the full plugin is a lot more complicated than that and I just don't know where to look anymore. I just don't know why drawInCGLContext stops being called. I've tried forcing it using CATransaction, it definitely gets sent the setNeedsDisplay message - but drawInCGLContext is never called. OpenGL doesn't report any errors either (I'm currently checking the results of all OpenGL calls). I'm confused! Help?
So, for anybody else who has this problem in future: You're trying to draw using the OpenGL context outside of the drawInCGLContext. There was a bug in the code where nearly all the drawing was happening from the correct place (drawInCGLContext) but one code path led to it rendering outside of there.
No errors are raised nor does glGetError return any problems. It just stops rendering. So if this happens to you - you're almost certainly making the same mistake I made!
I'm writing a video annotation application with Qt4 in which users need to be able to seek to various points in a video, putting markers on various objects and then setting keypoints for those markers so that they stay on the objects in the video as they move around. QGraphicsItemAnimation seems like a great place to start for these markers, however they need to be able to appear and disappear at specific times, which I can't figure out how to do with the QGraphicsItemAnimation. I could set the scale at 0 to make the objects disappear, but that seems like a pretty hacky solution, and I'm guessing that the paint engine would still waste cpu cycles trying to draw those invisible objects. Does anyone have a better solution than this? I'm using Qt 4.5.3 right now, but I'm willing to upgrade to 4.6 if it makes things easier. Thanks!!
It seems like the functionality you want of showing/hiding QGraphicsItem objects is beyond the scope of the simple "tweening" that the animation class performs. It is only for one object at a time, and any appearance or disappearance you have to write yourself.
You still might get some mileage out of QGraphicsItemAnimation (although the fact that it uses its own timer instead of being locked to the frame clock of your video is a little dodgy).
Neglecting "seeking" for a moment, there is a QTimeLine::finished() signal. If you let the end of an annotation's active animation timeline represent the point where you want it to disappear, you can trigger QGraphicsItem::hide() at that point. When it comes time to turn it back on, you would construct a new QGraphicsItemAnimation (based on the next run of keyframe data for that object) and call QGraphicsItem::show().
Note that one of the headlining features of Qt 4.6 is the QtAnimation framework, which is more sophisticated but also rather complex. I've not used it yet, but looking over the examples it seems like you might be able to "animate" a visibility or opacity property.