I'm making a 3D game in unity where the object should move forward and backward as the android device moves/accelerates in the Z axes. ie. When the player moves the devise in the direction of the +ve Z axis, the object should move forward, and when the player moves the devise in the direction of the -ve Z axis, the object should move backward.
This game is a multiplayer game, and the players will move in a large football field.
My idea to do this is using the accelerometer to calculate the acceleration of the device, then integrate the data of acceleration to get the device speed in the Z axis. and use the speed to move the device.
Using this equation
V2=V1 + ΔA . ΔT
Where
V2 : final velocity.
V1 : initial velocity.
ΔA : difference between the initial and final acceleration.
ΔT : difference between the initial and final time.
At first I tried to use kinematic equations to calculate the final speed, but I realized then that it can be only used when acceleration is constant. So a friend of me who studies physics differentiated this equation for me to use it when acceleration is variable.
I know that there will be some error in calculating the accurate displacement, and that the error will increase after the integration of acceleration, but this small percentage of error is okay for my application; I thought at first in using GPS instead of accelerometer but I found that GPS accuracy will be less than the sensors.
I know also that the error will be incredibly high after some time, so I reset the values of acceleration and velocity every 10 seconds. I'm also using a low-pass filter to reduce the noise of the sensor.
public class scriptMove : MonoBehaviour
{
const float kFilteringFactor = 0.1f;
public Vector3 A1;
public Vector3 A2;
public Vector3 A2ramping; // for the low-pass filter
public Vector3 V1;
public Vector3 V2;
public int SpeedFactor=1000; //this factor is for increasing acceleration to move in unity world
void resetAll()
{
Input.gyro.enabled = true;
A2 = Vector3.zero;
V1 = Vector3.zero;
V2 = Vector3.zero;
A2ramping = Vector3.zero;
}
// Use this for initialization
void Start()
{
InvokeRepeating("resetAll", 0, 10);
}
//http://stackoverflow.com/a/1736623
Vector3 ramping(Vector3 A)
{
A2ramping = A * kFilteringFactor + A2ramping * (1.0f - kFilteringFactor);
return A - A2ramping;
}
void getAcceleration(float deltaTime)
{
Input.gyro.enabled = true;
A1 = A2;
A2 = ramping(Input.gyro.userAcceleration) * SpeedFactor;
V2 = V1 + (A2 - A1) * deltaTime;
V1 = V2;
}
//Update is called once per frame
void Update()
{
getAcceleration(Time.deltaTime);
float distance = -1f;
Vector3 newPos = transform.position;
transform.Translate(Vector3.forward * Time.deltaTime * V2.z * distance);
}
}
The problem:
My code doesn't work always as expected when I move with the device;
- Sometimes when I move forward (in the +ve Z axis of the device) the object moves forward also, but sometimes it doesn't move at all.
- Sometimes when I'm still in my position the object moves alone by itself.
- Sometimes when I move forward and suddenly stop, the object does not stop.
My questions:
- Are those strange behaviors because of the accuracy of the device, or is there something I'm missing in my code.
- If I'm missing something in my code, What is it?
- I searched a lot about methods to get the most accurate position of the device, and I found that I can integrate GPS with accelerometer, how can I do this with my code in unity?
