Taking the Development Ahead - Learn OpenGL ES: For Mobile Game and Graphics Development - page 230

Listing 6-9. TANK FENCE GAME 3/src/com/apress/android/tankfencegame3/
Missile.java

public class Missile {
private float _sourcePositionX;
private float _sourcePositionY;
private float _sourcePositionZ;
private float _destinationPositionX;
private float _destinationPositionY;
private float _destinationPositionZ;
private float _angleZ;
private float _slopeZ;
private float _interceptY;

public Missile(float positionX, float positionY,
float positionZ, float angleZ) {
_sourcePositionX = positionX;
_sourcePositionY = positionY;
_sourcePositionZ = positionZ;
_destinationPositionX = positionX;
_destinationPositionY = positionY;
_destinationPositionZ = positionZ;
_angleZ = angleZ;
_slopeZ = (float)
Math.tan(Math.toRadians(_angleZ + 90));
_slopeZ = filter(_slopeZ);

_interceptY = positionY - (_slopeZ * positionX);

}
private float filter(float slope) {
boolean sign;

if(slope >= 0) {
sign = true;
} else {
sign = false;

}

slope = Math.abs(slope);
if(slope <= 0.25f) {