render on event rather than timer

(7 posts) (4 voices)

Started 1 year ago by yafusername
Latest reply from yafusername

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yafusername
Member

ive been experimenting with sparrow over the past week or so. awesome lib.

is there any way to avoid rendering on a nstimer.?! or at least drop the timer to fire every 1sec (or therabout) as a backup.

yet i want to render on events on touch events or changed in some critical attributes: size, color, position, etc.

im examining the demo code. the scenes 'multitouch' , 'text' , has no need to render at 30 - 60 fps. when sparrowview.framerate = 1.0f. the animation is drastically effected.

ideally, it wil render only touched objects that have changed, that would be a super christmas present. a bulk render of nsdrawableobjects when one changes is ok. and christmas is over.

im guessing its possible and SPEvent has something to do with it.

any pointers would be appreciated.

Posted 1 year ago #
Daniel
Primary Feather

If I understand you correctly, you'd like to draw only what has changed since the last frame, right? Like UIKit does it.

OpenGL works a little different in that respect. In OpenGL, the complete scene is drawn once per frame. That's because OpenGL was created with 3D scenes in mind, where nothing else makes sense.

So all that I could do is temporarily lower the framerate if nothing is moving. But finding out how much change there is would be difficult, because of the dynamic nature of the display tree. Anybody overriding a render method could move something without Sparrow knowing about it.

Thus, that kind of optimization is better done on application-level. Take the multitouch scene of the demo for example: in the touch events, you could change the framerate to a very low number when no finger is touching the scene. As soon as you've got touch events, the framerate can be raised again.

I hope that explains it well enough and gets you started!

Posted 1 year ago #
yafusername
Member

Yes. Its similar to Apple's CoreGraphics (UIKit?) implementation. Interestingly, its been suggested that CoreGraphics is backed by OpenGL. I find that hard to believe: for one, why take something confusing and introduce further eccentricities. In contrast to Sparrow's clean public interface.

I'm guessing you mean change the SPView framerate? Does that disable the NSTimer and start a new one (each call), or put a sleep in the timer loop.

Regards

Posted 1 year ago #
Shilo
Master Sparrow

Yes, self.stage.framerate to get/set framerate. When the framerate is changed, it will stop and start the timer for the run loop.

OpenGL is a cross platform graphics library, and Quartz 2D/Core Graphics is an Apple specific graphics library. As far as I can tell, OpenGL ES is lower level. Although I prefer OpenGL ES since I've hardly touched Core Graphics, but Core Graphics definently has nice features that OpenGL ES doesn't have.

I've tried to do an event-driven render system out of curiosity while having the render stopped but then the touch events never got dispatched. I assume if you set the framerate really low, it will have an unwanted lag between touch and event dispatch.

Posted 1 year ago #

Ok, with some testing, having the framerate at 1 doesn't create any lag with the touch events. My results are actually much better then I expected.

Here is a video of my results: SparrowRenderOnTouch.mov

Here is a simplified version of what i did:

Inside AppDelegate.m:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    SP_CREATE_POOL(pool);
 
    [SPStage setSupportHighResolutions:YES];
    [SPAudioEngine start];
 
    Game *game = [Game alloc];
    sparrowView.stage = game;
    game = [game init];
    [game release];
 
    [window makeKeyAndVisible];
    [sparrowView start];
 
    SP_RELEASE_POOL(pool);
 
    return YES;
}

This is so that the stage is linked before the init method.

Game.h:

 
#import <Foundation/Foundation.h>
#import "Sparrow.h"
 
@interface Game : SPStage {
}
 
- (void)addQuadWithX:(int)x y:(int)y;
@end

Game.m:

#define SP_RENDERSTAGE() [self.stage.nativeView renderStage]
 
#import "Game.h"
 
@implementation Game
- (id)initWithWidth:(float)width height:(float)height {
	if (self = [super initWithWidth:width height:height]) {
		self.stage.frameRate = 1;
		[self addEventListener:@selector(onEnterFrame:) atObject:self forType:SP_EVENT_TYPE_ENTER_FRAME];
		[self addEventListener:@selector(onTouch:) atObject:self forType:SP_EVENT_TYPE_TOUCH];
    }
    return self;
}
 
- (void)onEnterFrame:(SPEnterFrameEvent *)event {
	NSLog(@"onEventFrame passedTime:%f", event.passedTime);
}
 
- (void)onTouch:(SPTouchEvent *)event {
	SPTouch *touch = [event.touches anyObject];
	if (touch.phase == SPTouchPhaseBegan || touch.phase == SPTouchPhaseMoved) {
		SPPoint *touchPosition = [touch locationInSpace:self];
		SPPoint *prevPosition = [touch previousLocationInSpace:self];
 
		int currentX = (int)prevPosition.x;
		int currentY = (int)prevPosition.y;
		int targetX = (int)touchPosition.x;
		int targetY = (int)touchPosition.y;
 
		float radians = atan2(currentX-targetX, currentY-targetY);
		int distance = sqrt(pow(abs(targetX-currentX), 2)+pow(abs(targetY-currentY), 2));
 
		int newX = currentX;
		int newY = currentY;
		for (int i=1; i<distance+1; i++) {
			[self addQuadWithX:newX y:newY];
			newX = currentX - (int)(sin(radians)*i);
			newY = currentY - (int)(cos(radians)*i);
		}
		[self addQuadWithX:newX y:newY];
 
		SP_RENDERSTAGE();
	}
}
 
- (void)addQuadWithX:(int)x y:(int)y {
	SPQuad *quad = [SPQuad quadWithWidth:10 height:10];
	quad.x = x - quad.width/2;
	quad.y = y - quad.height/2;
	quad.color = SP_COLOR((int)([SPUtils randomFloat]*255), (int)([SPUtils randomFloat]*255), (int)([SPUtils randomFloat]*255));
	quad.rotation = SP_D2R([SPUtils randomFloat]*360);
	[self addChild:quad];
}
 
- (void)dealloc {
	[self removeEventListener:@selector(onTouch:) atObject:self forType:SP_EVENT_TYPE_TOUCH];
	[self removeEventListener:@selector(onEnterFrame:) atObject:self forType:SP_EVENT_TYPE_ENTER_FRAME];
	[self removeAllChildren];
	[super dealloc];
}
@end

Notice the line:

#define SP_RENDERSTAGE() [self.stage.nativeView renderStage]

This is how you will want to rendering the stage on event, whether it's a custom event or a touch event. I just used a define cause i think its cooler that way. Also, XCode will give you a warning saying:

warning: no '-renderStage' method found

This is only because this method is hidden inside SPView, but it's still callable!

So to get rendering on event, you can set the frameRate to 1 and on the event, just call "[self.stage.nativeView renderStage]".

Posted 1 year ago #

freerunnering
Moderator

Very neat trick thanks!!

Posted 1 year ago #
yafusername
Member

Shilo,

Touch events should not be delayed; in fact, are they not on a different thread?!

It appears you are calling the render on an touch event, rather than reset the fps to say 30. because why bother. Good thinking there. I suppose this should be on any drawing object, or SPDisplayObject.

BTW. Thanks for the attention. I like your code; its very readable like Daniels.

Posted 1 year ago #

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render on event rather than timer

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