How to make simple tilting function on the iPhone

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Hi,

I'm trying to create a simple tilt function using the iPhone's accelerometer in Unity. I've looked at a lot samples but can't get it to work the way I want. My App basically has a 2D character. What I'm trying to do is:

//pseudocode if(tiltleft > 0) { //do something }

if(tiltright > 0) { //do something }

Could someone advice me on how to approach this or point me to a good tutorial on accelerometers please?

Thanks in advance,

Hakimo

Answer 1

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Answer by Thom Denick · Jul 28, 2010 at 05:46 AM

There's a decent example for multi-dimensional tilt functionality in the iPhone Unity documentation, but I actually just messed around with getting this working in my project last night.

I think we have the same problem - apply the tilt along X to the X coordinate of our character in a 2D plane. Here's how I got it working... This is in C# and is based on the iPhone controls documentation.

public float TiltSpeed = 5.0f;

void FixedUpdate() {
            float tiltAngle = iPhoneInput.acceleration.x;

         tiltAngle *= Time.deltaTime;
         tiltAngle *= TiltSpeed;

         // Move object - Change this to transform.position if you don't have a rigid body on your char.
         rigidbody.AddForce(tiltAngle, 0, 0);

Obviously, you need to test this on the device or with Unity Remote. I actually have a script that displays my devices tilt amount onGUI so I can see precisely what kind of X values the device is returning.

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Hakimo · Jul 28, 2010 at 08:24 AM 0

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Wow, that looks easier than what I have tried. I even got to see the values as well. Although I'm a bit stuck at the moment with the if conditions. I'm using print(transform.position.x) to get the values. I tried to use: if(transform.position.x == -0.1) { //do something } Unfortunately nothing works. What value should the conditions be? I even used tiltAngle but nothing happens.

Thanks again,

Hakimo · Jul 28, 2010 at 09:50 AM 0

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It's alright, manage to do something. I didn't check the value properly for it to make any effect. Thanks again. Also, where did you learn about accelerators? The one example I followed earlier made so many variables that I didn't quite understand what it was doing :P

Thom Denick · Jul 28, 2010 at 08:26 PM 0

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This is all modified from the Help documentation in Unity under the iPhoneInput script reference. I do think the example could have been simpler, but I guess they wanted to show that generally for a ball rolling around you would want to be polling at least two coordinates.

Hakimo · Jul 29, 2010 at 02:21 AM 0

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Thanks again. Just wanted to understand more about the coding; How does the float TiltSpeed effect the tilt? I can't seem to see any dramatic changes. Also, when you assigned TiltSpeed to tiltAngle, does it override the Time.deltaTime? I didn't know you can assign 2 values to a variable. Thanks again for the help :)

Thom Denick · Jul 29, 2010 at 03:51 AM 0

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Hi Hakimo,

Float is a type of number that can hold decimals. Since the Input is a decimal number, it's perfect for holding the X Acceleration.

In the next two I'm multiplying the TiltAngle. Multiplying movement deltaTime is a way of ensuring that you move based on the time and not by Frames (which can vary by FPS). Second, I multiply by our tilt speed which is the variable that affects how much our character moves based on the tilt.

Answer 2

Answer by cregox · Jan 28, 2011 at 10:28 PM

As Smorpheus suggested, to use the accelerometer I've got the Controller.js from Unity's Roll-a-ball iPhone example: http://unity3d.com/support/resources/example-projects/iphone-examples.html

Maybe it's not exactly what you needed, but I guess it's related enough, a good hint and good to document. It's quite simple and I even simplified it a little:

public float force = 9.8f;

void FixedUpdate ()
{
    dir.x = Input.acceleration.x;
    dir.y = Input.acceleration.y;
    Physics.gravity = dir * force;
}

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