public void OnSensorChanged(SensorEvent e)
{
if (e.Sensor.Type != SensorType.Accelerometer)
{
return;
}
// Record the accelerometer data, the event's timestamp as well as
// the current time. The latter is needed so we can calculate the
// "present" time during rendering. In this application, we need to
// take into account how the screen is rotated with respect to the
// sensors (which always return data in a coordinate space aligned
// to with the screen in its native orientation).
switch (display.Rotation)
{
case SurfaceOrientation.Rotation0:
sensor_values.Set(e.Values[0], e.Values[1]);
break;
case SurfaceOrientation.Rotation90:
sensor_values.Set(-e.Values[1], e.Values[0]);
break;
case SurfaceOrientation.Rotation180:
sensor_values.Set(-e.Values[0], -e.Values[1]);
break;
case SurfaceOrientation.Rotation270:
sensor_values.Set(e.Values[1], -e.Values[0]);
break;
}
sensor_timestamp = e.Timestamp;
cpu_timestamp = DateTime.Now.Ticks;
}
public void ComputePhysics(float sx, float sy, float dT, float dTC)
{
// Force of gravity applied to our virtual object
float m = 1000.0f; // mass of our virtual object
float gx = -sx * m;
float gy = -sy * m;
// ·F = mA <=> A = ·F / m We could simplify the code by
// completely eliminating "m" (the mass) from all the equations,
// but it would hide the concepts from this sample code.
float invm = 1.0f / m;
float ax = gx * invm;
float ay = gy * invm;
// Time-corrected Verlet integration The position Verlet
// integrator is defined as x(t+Æt) = x(t) + x(t) - x(t-Æt) +
// a(t)Ætö2 However, the above equation doesn't handle variable
// Æt very well, a time-corrected version is needed: x(t+Æt) =
// x(t) + (x(t) - x(t-Æt)) * (Æt/Æt_prev) + a(t)Ætö2 We also add
// a simple friction term (f) to the equation: x(t+Æt) = x(t) +
// (1-f) * (x(t) - x(t-Æt)) * (Æt/Æt_prev) + a(t)Ætö2
float dTdT = dT * dT;
float x = Location.X + friction * dTC * (Location.X - prev_location.X) + accel.X * dTdT;
float y = Location.Y + friction * dTC * (Location.Y - prev_location.Y) + accel.Y * dTdT;
prev_location.Set(Location);
Location.Set(x, y);
accel.Set(ax, ay);
}
protected override void OnSizeChanged(int w, int h, int oldw, int oldh)
{
// Compute the origin of the screen relative
// to the origin of the bitmap
origin.Set((w - ball_bitmap.Width) * 0.5f, (h - ball_bitmap.Height) * 0.5f);
Bounds.X = (((float)w / (float)meters_to_pixels_x - BALL_DIAMETER) * 0.5f);
Bounds.Y = (((float)h / (float)meters_to_pixels_y - BALL_DIAMETER) * 0.5f);
Console.WriteLine(Bounds.X);
}