Drone Grid Case Study: Creating the Player - Beginning Android 3D Game Development - page 259

The function does the following:

Creates an integer array View that holds the current screen view parameters of
the Android device.

1.

Calls MapWindowCoordsToWorldCoords() function with the view parameters,
along with the x and y locations that the user has touched and a z value of
1. The 3D homogeneous world coordinates are returned in the WorldCoords
float array.

2.

3. Converts the homogeneous coordinates to Cartesian coordinates by dividing

WorldCoords by the w value or fourth element in the WorldCoords array. The
result is stored in TargetLocation .

Defines the WeaponLocation variable as the location of the camera or viewer.

4.

Defines the Direction variable, which is the direction the weapon is to be
fired, as a vector going from the WeaponLocation to the TargetLocation .

5.

Fires the player's weapon with the projectile starting at the WeaponLocation
location and in the direction Direction .

6.

7. Plays the player's weapon sound effect.

Listing 7-62. Checking the User's Touch for Firing the Weapon

void CheckTouch()
{
// Player Weapon Firing
int[] View = new int[4];
View[0] = 0;
View[1] = 0;
View[2] = m_ViewPortWidth;
View[3] = m_ViewPortHeight;
float[] WorldCoords = MapWindowCoordsToWorldCoords(View, m_TouchX, m_TouchY, 1);
// 1 = far clipping plane
Vector3 TargetLocation = new Vector3(WorldCoords[0]/WorldCoords[3],
WorldCoords[1]/WorldCoords[3], WorldCoords[2]/WorldCoords[3]);
Vector3 WeaponLocation = m_Camera.GetCameraEye();
Vector3 Direction = Vector3.Subtract(TargetLocation, WeaponLocation);
if ((Direction.x == 0) && (Direction.y == 0) && (Direction.z == 0))
{
return;
}
if (m_Weapon.Fire(Direction, WeaponLocation) == true)
{
// WeaponFired
PlayPlayerWeaponSound();
}
}