CCSprite not getting redrawn fast enough using UIAccelerometer?

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CCSprite not getting redrawn fast enough using UIAccelerometer?

(27 posts) (3 voices)

Started 5 months ago by Objective Zero
Latest reply from Objective Zero

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Objective Zero
Member
Hey,

In my game, my main character is a CCSprite. That CCSprite is controller by the UIAccelerometer, I enabled the accelerometer method by doing self.isAccelerometerEnabled = YES; And then setting the updateInterval to: 1/30.

The problem is not my acceleration values not being actual good values but it has to do with my CCSprite not getting redrawn fast enough. So pretty much if my CCSprite moves many pixels per .1 second, the sprite starts to flicker and then the faster it gets the more it flickers.

I declared my acceleration values in my .h and set them in the Accelerometer delegate method then I set the position of the CCSprite in my game loop.

Here is my Accelerometer code (some of it):
```
float accelX = (acceleration.x - [[NSUserDefaults standardUserDefaults] floatForKey:@"X-Calibrate"]);
rollingX = (accelX * kFilteringFactor) + (rollingX * (1.0 - kFilteringFactor));
AccelPoint.x += (rollingX*50);
```
Any ideas why this might be happening?

Thanks!
Posted 5 months ago #
clarus
Member
A couple suggestions.

First, don't keep hitting the user preferences in a method like this. That's much slower than you need. Do it the first time, and then cache the value, like:
```
static CGFloat    xCal = 9999;

if (xCal == 9999)
   xCal = [[NSUserDefaults standardUserDefaults] floatForKey:@"X-Calibrate"];
```
Secondly, I think if you log the positions you're setting your sprite to in the update, you're going to see huge skips between locations. I wouldn't set the actual position for the sprite in your accelerator delegate, but instead create an acceleration or velocity that you use in your update method to modify the sprite's position over time--you might be able to use your current rollingX and rollingY values from your delegate method.

Someone else probably has an example of this, but the idea is to use the accelerometer delegate to determine how to affect the sprite's position, not set explicit positions for the sprite. Then in your update method, modify the sprite using the current rollingX and rollingY values or whatever. Once you get the basics working, you can look at smoothing it more by doing an ease-in type acceleration if it makes sense for your game.

Of course, if you're using physics for your game, you'll modify the object's physics model rather than the sprite. But the same idea applies--don't have the accelerometer delegate calculate absolute positions.
Posted 5 months ago #
slembcke
Administrator

The timing of the accelerometer events won't line up with the timing of rendering frames even if you set both to be the same rate. Store the values passed to you from the accelerometer delegate and apply smoothing/process them in your main update loop.

Posted 5 months ago #
Objective Zero
Member

Ok so pretty much this is what I am doing ATM. I am getting my acceleration.x values from the delegate method and smoothing them IN that method. I then set the position of my character to those values in my game loop. This still causes the same issue as I was originally facing so what should I do instead?

Posted 5 months ago #
Objective Zero
Member
Ok so now I finally got to this issue!
My character is still having this same issue. This is the code I am using:
```
- (void) accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
	//Calibration
    float accelX = (acceleration.x - calibrationFloat);
    //Low Pass Filter
    rollingX = (accelX * kFilteringFactor) + (rollingX * (1.0 - kFilteringFactor));
	AccelPoint.x += (rollingX*50);
}
```
Then in my game loop:
pos = sprite.position;
pos.x = AccelPoint.x;
pos.y += cocosVelocity.y;
sprite.position = ccp(pos.x, pos.y);

A few things:
1. My FPS is at 55+ at all times
2. My kFilteringFactor is 0.2

Any ideas?
Posted 5 months ago #
Objective Zero
Member

bump?

Posted 5 months ago #
clarus
Member
What we were saying is to move all of the non-accelerometer-reading code to your update loop. Also, I don't understand what that rollingX calc is doing. This is a typical accelerometer delegate method:
```
- (void) accelerometer: (UIAccelerometer *) accelerometer didAccelerate: (UIAcceleration *) acceleration
{
    // Use a basic low-pass filter to only keep the gravity in the accelerometer values for the X and Y axes
    m_accelerationX = acceleration.x * kFilteringFactor + m_accelerationX * (1.0 - kFilteringFactor);
    m_accelerationY = acceleration.y * kFilteringFactor + m_accelerationY * (1.0 - kFilteringFactor);
    m_accelerationZ = acceleration.z * kFilteringFactor + m_accelerationZ * (1.0 - kFilteringFactor);

    // Do something.
}
```
So, above I have these in my instance vars:
UIAccelerationValue m_accelerationX;
UIAccelerationValue m_accelerationY;
UIAccelerationValue m_accelerationZ;

Do that, but it looks like you only care about the X axis.

Then in your update method, read those values and do the calculation.

One other thing I'd do. Instead of this:
```
<set up pos like you want to based on the accelerometer>
sprite.position = ccp(pos.x, pos.y);
```
do
```
<set up pos like you want to based on the accelerometer>
CGPoint floorPos = ccp(floorf(pos.x), floorf(pos.y));
if (!CGPointEqualToPoint(sprite.position, floorPos)
    sprite.position = floorPos;
```
The difference is the first code will try to position on subpixel boundaries, and it sets the position of the sprite even when it hasn't changed pixel boundaries. setPosition actually marks things as dirty, so you're causing extra work if the position hasn't really changed.
Posted 5 months ago #
Objective Zero
Member

Alright I will try that but with the rollingX I am trying to combine my calibrated Accelerometer value from my other view with my kFilterFactor to stop the jitterness all in one variable. Is that possible? Thats what I was trying to do with it.

Posted 5 months ago #
clarus
Member

The rollingX thing might make sense, but move this out of the accelerometer code and into your update:

AccelPoint.x += (rollingX*50);

Posted 5 months ago #
Objective Zero
Member

Wow that works great! My character looks like its at 60FPS now too! But one tiny issue, before I did those 2 changes, I had code similar to Doodle Jump where if the character went off the right of the screen it would come back on from the left and vice versa but something with this code messed that up. Any ideas on that?

Posted 5 months ago #
clarus
Member

There must have been something, probably in your update method that was wrapping the position. I don't see anything above that was doing that, but take a look through your code. probably AccelPoint.x or maybe the sprite position.x itself was being checked and set back to the other side. Find that code and move it to where you're setting up pos in your update. Have it check the pos.x value and modify it accordingly.

Posted 5 months ago #

Objective Zero
Member

This is my code to do that:

CGSize size = [CCDirector sharedDirector].winSize;
    if (sprite.position.x >= size.width) {
        pos.x -= size.width;
    } else if (sprite.position.x < 0.0f) {
        pos.x += size.width;
    }

But I do this in my update method before I set the sprite.position so maybe I should do it somewhere else?

Posted 5 months ago #

clarus
Member

Do it like this.

Right after:

CGPoint floorPos = ccp(floorf(pos.x), floorf(pos.y));

Add:

CGSize size = [CCDirector sharedDirector].winSize;

    if (floorPos.x >= size.width) {
        floorPos.x -= size.width;
    } else if (floorPos.x < 0.0f) {
        floorPos.x += size.width;
    }

Posted 5 months ago #

Objective Zero
Member

Hmm it almost works. The problem is if trigger to the right->left or vice versa more than 2 times, my sprite just disappears for some odd reason. Any ideas?

Posted 5 months ago #
clarus
Member

Can you post this whole section of code that sets up the sprite position?

Posted 5 months ago #

Objective Zero
Member

Is this enough?:

CGPoint floorPos = ccp(floorf(pos.x), floorf(pos.y));
    //Right to Left and vice cersa
    CGSize size = [CCDirector sharedDirector].winSize;
    if (floorPos.x >= size.width) {
        floorPos.x -= size.width;
    } else if (floorPos.x < 0.0f) {
        floorPos.x += size.width;
    }
    //Efficiency for position of sprite
    if (!CGPointEqualToPoint(sprite.position, floorPos)) {
        sprite.position = floorPos;
    }

Posted 5 months ago #

clarus
Member

Try this:

CGPoint floorPos = ccp(floorf(pos.x), floorf(pos.y));

    //Efficiency for position of sprite
    if (!CGPointEqualToPoint(sprite.position, floorPos)) {
        //Right to Left and vice cersa
        CGSize size = [CCDirector sharedDirector].winSize;
        if (floorPos.x >= size.width) {
            floorPos.x -= size.width;
        } else if (floorPos.x < 0.0f) {
            floorPos.x += size.width;
        }
        sprite.position = floorPos;
    }

Posted 5 months ago #

Objective Zero
Member

nope didn't work, still the same issue as before :(

Posted 5 months ago #
clarus
Member

Ok, then put it back the way it was before. I like that better.

I don't think it's this code. Is pos being reloaded from the sprite each time or is that or something else setting its x position independently of the sprite?

Add this after the "sprite.position =" code and see what it logs when the sprite goes missing.

NSLog(@"sprite.position = (%3.2f,%3.2f)", sprite.position.x,sprite.position.y);

Posted 5 months ago #
Objective Zero
Member

So the position.x keeps increasing, mine got to around 2000 so I think thats the issue.

Posted 5 months ago #
clarus
Member

Is it because that AccelPoint.x is getting too big? You should at least reset that when you wrap the sprite around, if not earlier.

Posted 5 months ago #
Objective Zero
Member

Yes that is most likely. What should I set Accelpoint.x to then in both scenarios? (0) and the (screen width) depending on which way it goes?

Posted 5 months ago #
clarus
Member
I'm guessing because I'm not seeing all of this code together, but right after you do this:

AccelPoint.x += (rollingX*50);

Do this:
```
//Right to Left and vice cersa
    CGSize size = [CCDirector sharedDirector].winSize;
    if (AccelPoint.x >= size.width) {
        AccelPoint.x -= size.width;
    } else if (AccelPoint.x < 0.0f) {
        AccelPoint.x += size.width;
    }
```
That should work unless the rollingX value is some monstrous number. And again, I'm not sure if I'm guessing correctly about how all this code is interacting. Give it a shot.
Posted 5 months ago #
Objective Zero
Member

PERFECT! It works great! Thanks again!

Posted 5 months ago #
Objective Zero
Member

Also one other thing, it I want to lower the Accelerometer sensitivity all I have to do is modify the number which I multiply correct?

Posted 5 months ago #
clarus
Member

Yes, change kFilteringFactor from .2 to .1 or .05, or whatever works for you.

Posted 5 months ago #
Objective Zero
Member

Yep that fixed it, thanks once again!

Posted 5 months ago #

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