Accelerometer based games smoothness

Question

Take Doodle Jump and other games that rely on the accelerometer. The movement of the character is very smooth and I have no idea how they implemented it. I've seen a number of SO/GameDev/forum questions, but the discussion ends abruptly when someone recommends a high/low pass filter. I've tried that (unless I'm missing something) and the results are nowhere near smooth.

All I'm trying to do is move a character on the x axis. This is the code I have and it's very "choppy". It's actually the code you can see on the official Android tutorials.

float alpha = 0.9f; //tried many values from 0.1f to 0.99f. chopiness still there @Override public void onSensorChanged(SensorEvent event) { if(event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) { if(init) { gravity[0] = event.values[0]; gravity[1] = event.values[1]; gravity[2] = event.values[2]; init = false; } else { gravity[0] = alpha * gravity[0] + (1 - alpha) * event.values[0]; gravity[1] = alpha * gravity[1] + (1 - alpha) * event.values[1]; gravity[2] = alpha * gravity[2] + (1 - alpha) * event.values[2]; } // Remove the gravity contribution with the high-pass filter. linear_acceleration[0] = event.values[0] - gravity[0]; linear_acceleration[1] = event.values[1] - gravity[1]; linear_acceleration[2] = event.values[2] - gravity[2]; character.setX(character.getX() - linear_acceleration[0]); }

I also tried multiplying linear_acceleration[0] with a sensitivity, where 0 < sensitivity < 1 but the choppiness still doesn't go away. What is the next step from here to achieve a smooth movement like in Doodle Jump?

It's not "high/low pass filters" that remove choppiness. It's low pass filters specifically. What you have is a high pass filter, which does not remove choppiness. — congusbongus
– congusbongus, Commented Apr 8, 2014 at 0:34
@congusbongus I'm implementing this now: stackoverflow.com/a/5780505/1991295 Still absolutely no difference. — async
– async, Commented Apr 8, 2014 at 17:04

async · Accepted Answer · 2014-04-12 08:15:49Z

OK, I managed to sort this out and it was a bit stupid. Yes, the low-pass filter DOES solve the problem. Actually here's my code (note I'm doing it in a different method, but just copy and paste the contents in onSensorChanged(SensorEvent) if you wish:

private static final float alpha = 0.65f; private static final float SENSITIVITY = 1f/128; private boolean firstTime = true; @Override public void handleSensorEvent(SensorEvent event) { if(firstTime) { vals[0] = event.values[0]; vals[1] = event.values[1]; vals[2] = event.values[2]; } vals[0] = vals[0] + alpha * (event.values[0] - vals[0]); vals[1] = vals[1] + alpha * (event.values[1] - vals[1]); vals[2] = vals[2] + alpha * (event.values[2] - vals[2]); character.setX( character.getX() - vals[0] * SENSITIVITY ); }

You can calibrate alpha and SENSITIVITY according to your needs. Now this is why this code was producing very choppy movement initially: in my activity's onResume() I was registering my listener using SensorEvent.SENSOR_DELAY_NORMAL. That is wrong. What you have to do is register it with SensorEvent.SENSOR_DELAY_GAME. I think the reason behind this is obvious. So in your activity's onResume():

sensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_GAME);

where accelerometer is declared as (in onCreate()):

accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

Stack Exchange Network

Accelerometer based games smoothness

1 Answer 1

You must log in to answer this question.

Hot Network Questions

Accelerometer based games smoothness

1 Answer 1

You must log in to answer this question.

Related

Hot Network Questions