Adding passed frames property to SPStage and SPEnterFrameEvent

Excelcius

Hi Daniel I would like to make a small feature request if I may, could you possibly add a passedFrames property to SPStage and SPEnterFrameEvent ?

Im currently implementing the following code in my enterFrame method, in my games base class and passing that variable to my scenes, along with the elapsed time variable which I still use for things like counting down delays ect, like so.

- (void) onEnterFrame:(SPEnterFrameEvent *)event
{
    double frametime = 1.0f / [SPStage mainStage].frameRate;
    int passedFrames = floor((remainingTime + event.passedTime) / frametime);

    remainingTime = fmod(remainingTime + event.passedTime, frametime);

    if([self sceneTransition:event] != ON)
    {}

    else if(current_Scene == GAME_SCREEN)
    {
        [gameScreen update:event.passedTime frames:passedFrames];
    }
}

But would prefer it if it was a pre calculated property of the EnterFrame event, that way I could just pass on the SPEnterFrameEvent to my update methods, making it neater and more robust. as you can see I have worked round the issue but it gets a little messy the more update methods I call. I was just thinking it would be a handy property to have for very little effort.

Thanks 🙂

Daniel

You mean the number of frames since the application start, right?

Couldn't you add a special event handler in your Game class that just counts up a "frameCount" property? That could then be accessed anywhere in your game.

Excelcius

Hi Daniel No what I mean is Im using a frame based animation and movement system for greater consistency so Im using passedFrames not passedTime, kind of like the SPMovieclip class does. It counts the number of frames which have passed since the last EnterFrameEvent call and uses that to calculate the distance traveled ect.

I have implemented it in my game but its feels a little messy to listen for the enterframe event and then create another event from it. So I thought I might make a feature request to implement the calculation like above in the advanceTime method of SPStage and then add a passedFrames property to the SPEnterFrameEvent, which would then be accessible globally without needing to write any code.

Just to extend on the idea further you could modify the movieclip class to use that passedFrames property instead of calculating the passed frames for each movieClip separately, making it a tiny bit more efficient.

Daniel

Hm ... actually, "passedFrames" will always be "1"! That's because it is called -- per definition -- once per frame.

In the SPMovieClip class, it actually works the other way round: it calculates how many frames *of the movieclip* have passed during "passedTime". And then it updates the displayed frame accordingly.

Do you understand what I mean?

So, if you want to do an animation with a fixed speed that is chained to the framerate, move your objects by a fixed delta.

This works even with tweens: just create a custom SPJuggler object and advance it once per frame (as usual), but not with the "passedTime", but a fixed value.

Excelcius

If I understand you correctly Thats exactly what Im getting at, this is how Im calculating my passedFrames

double frametime = 1.0f / [SPStage mainStage].frameRate;
int passedFrames = floor((remainingTime + event.passedTime) / frametime);

remainingTime = fmod(remainingTime + event.passedTime, frametime);

So if 0.201 seconds passed between updates at 60fps the above calculation returns 12 passedframes with a remainder of 0.001 seconds to be passed onto the next update.

I was just making a feature request to add this calculation to SPStage and add the passedFrames property to SPEnterFrameEvent, so either passedTime or passedFrames could be used in Enterframe events, without having to add that calculation each time or create another event for example in SPStage

- (void)advanceTime:(double)seconds
{
    // advance juggler
    [mJuggler advanceTime:seconds];

    double frametime = 1.0f / [SPStage mainStage].frameRate;
    int passedFrames = floor((remainingTime + seconds) / frametime);

    remainingTime = fmod(remainingTime + seconds, frametime);

    // dispatch EnterFrameEvent
    SPEnterFrameEvent *enterFrameEvent = [[SPEnterFrameEvent alloc]
        initWithType:SP_EVENT_TYPE_ENTER_FRAME
          passedTime:seconds
        passedFrames:passedFrames];

    [self broadcastEvent:enterFrameEvent];
    [enterFrameEvent release];
}

Then it could be accessed like so

- (void) onEnterFrame:(SPEnterFrameEvent *)event
{
    for(int i = 0; i < event.passedFrames; i++)
   {
        self.x += xVelocity;
        self.y += yVelocity;

        //perform collision detection ect
   }
}