InFOV.java

 private boolean isInFieldOfVision(vi entityPlayer, ia entity)
  {
    
		double d = par1Entity.posX - posX;
        double d2 = par1Entity.posZ - posZ;
        double d1;

        if (par1Entity instanceof EntityLiving)
        {
            EntityLiving entityliving = (EntityLiving)par1Entity;
            d1 = (posY + (double)getEyeHeight()) - (entityliving.posY + (double)entityliving.getEyeHeight());
        }
        else
        {
            d1 = (par1Entity.boundingBox.minY + par1Entity.boundingBox.maxY) / 2D - (posY + (double)getEyeHeight());
        }
        double d3 = MathHelper.sqrt_double(d * d + d2 * d2);
        float f123 = (float)((Math.atan2(d2, d) * 180D) / Math.PI) - 90F;
    float f1234 = (float)(-((Math.atan2(d1, d3) * 180D) / Math.PI));
    float f1 = -updateRotation(rotationPitch, f1234, 360.0);
    float f2 = updateRotation(rotationYaw, f123, 360.0F);

float f4 = 70.0F; //horizonal angle 
    float f5 = 65.0F; //verticle angle
    float f6 = entityPlayer.y - f4;
    float f7 = entityPlayer.y + f4;
    float f8 = entityPlayer.z - f5;
    float f9 = entityPlayer.z + f5;
    boolean flag = GetFlag(f6, f7, f, 0.0F, 360.0F);
    boolean flag1 = GetFlag(f8, f9, f1, -180.0F, 180.0F);
    return (flag) && (flag1);
  }

  public boolean GetFlag(float f, float f1, float f2, float f3, float f4) {
    if (f < f3)
    {
      if (f2 >= f + f4)
      {
        return true;
      }
      if (f2 <= f1)
      {
        return true;
      }
    }
    if (f1 >= f4)
    {
      if (f2 <= f1 - f4)
      {
        return true;
      }
      if (f2 >= f)
      {
        return true;
      }
    }
    if ((f1 < f4) && (f >= f3))
    {
      return (f2 <= f1) && (f2 > f);
    }

    return false;
  }