Center for Analysis and Design of Intelligent Agents

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Lab Project

Follow these steps to complete the lab project:

Create a New Project Create a new empty project called “Lab4” in the same way you have created new projectsfor other lab projects.

Plug in and Test Joypad Plug a USB joypad into your computer and find the device in your system's control panel (usually under “Devices and Printers”). Examine the device properties and find a small test panel for the device. Make sure the device works. Intall necessary drivers if the system is not picking it up.

Initialize Joystick Input Your MyFrameListener class needs to receive callbacks from the joystick device and therefore has to inherit joystick callback methods from an abstract class called OIS::JoyStickListener. Luckily you can inherit from multiple classes! Change your declaration of your MyFrameListener into this:

class MyFrameListener : public Ogre::FrameListener, public OIS::JoyStickListener {

You then have to provide implementations of a few abstract callback methods:

bool axisMoved(const OIS::JoyStickEvent &e, int axis);
bool buttonPressed(const OIS::JoyStickEvent &arg, int button);
bool buttonReleased(const OIS::JoyStickEvent &arg, int button);
bool povMoved(const OIS::JoyStickEvent &arg, int pov);
 
bool MyFrameListener::axisMoved(const OIS::JoyStickEvent &e, int axis) {
	return true;
}
bool MyFrameListener::buttonPressed(const OIS::JoyStickEvent &arg, int button) {
	return true;
}
bool MyFrameListener::buttonReleased(const OIS::JoyStickEvent &arg, int button) {
	return true;
}
bool MyFrameListener::povMoved(const OIS::JoyStickEvent &arg, int pov) {
	return true;
}

In this class you need a new member variable to hold a pointer to a new joystick input object (e.g. OIS::JoyStick* _Joystick;) and then you have to create this object in your constructor. Because it is not guaranteed that the joypad is connected, you need to catch a possible exception upon creation and let the application gracefully continue even if the creation fails:

try {
	_Joystick = static_cast<OIS::JoyStick*>(_InputManager->createInputObject( OIS::OISJoyStick, true ));
	_Joystick->setEventCallback(this);
	std::cout << "Successfuly created Joystick";
}
catch(...) {
	std::cout << "Failed to initialize Joystick";
	_Joystick = 0;
}

Don't forget to also destroy the joystick object in your destructor, just like you do with the mouse and keyboard. Make sure this code compiles and check to see if your joypad gets properly initialized.

Move Character with POV Now you want to give players the option to move the character by pressing one of the directions on the POV (point of view) digital button on the left of the joypad. You should still retain the keyboard control of the movement. First explore the values you get when you press the POV button.

// Create a member variable in the MyFrameListener class: int _povState
 
bool MyFrameListener::povMoved(const OIS::JoyStickEvent &arg, int pov) {
	_povState = arg.state.mPOV[pov].direction;
	std::cout << _povState << "\n";
	return true;
}

Notice that you get special codes for each direction and the code 0 when you let go of the button (it goes back into center position). Unlike the keyboard, you don't get continuous events when you press and hold the directions! To use this for moving the character you need to store the last direction code received and reset it when you receive 0. In the same callback (below the two lines above), add the following OR operation to your keyboard movement if statements:

if (_Keyboard->isKeyDown(OIS::KC_UP) || _povState == OIS::Pov::North) {
	SinbadTranslate += Ogre::Vector3(0, 0, -1);
	walked = true;	
	_rotation = 3.14f;
}
if (_Keyboard->isKeyDown(OIS::KC_DOWN) || _povState == OIS::Pov::South) {
	SinbadTranslate += Ogre::Vector3(0, 0, 1);
	walked = true;	
	_rotation = 0.0f;
}
if (_Keyboard->isKeyDown(OIS::KC_LEFT) || _povState == OIS::Pov::West) {
	SinbadTranslate += Ogre::Vector3(-1, 0, 0);
	walked = true;	
	_rotation = -1.57f;
}
if (_Keyboard->isKeyDown(OIS::KC_RIGHT) || _povState == OIS::Pov::East) {
	SinbadTranslate += Ogre::Vector3(1, 0, 0);
	walked = true;	
	_rotation = 1.57f;
}

Finally, you need to capture the joystick input in this frameStarted method:

if( _Joystick ) 
	_Joystick->capture();

Rotate Camera with Analog Stick Now you should try to rotate (or swivel) the camera around the character with the right analog stick on the joypad. You first need to create a new member variable in your MyFrameListener class that stores the current camera angle (e.g. float _camangle). In your constructor, initialize this angle to the value -1*Ogre::Math::HALF_PI so that this angle corresponds to the initial orientation of the character. As with the POV button, you should examine the values you get from the analog axes of your joypad. Add the following lines to your axisMoved callback:
```
int value = e.state.mAxes[axis].abs;
switch(axis) {
	case 1:
	std::cout << "1:" << value << "\n";
	break;
}
```
You can add more cases to this to observe values along the other axes. You will notice that they each run from a negative 32768 to a positive 32767, which corresponds to the range of a 16-bit signed integer. For one of these axes, we want this range to map onto a camera angle that runs from 0 to 360 degrees (calculated in radians). The camera angle can therefore be calculated as follows:
```
_camangle = Ogre::Math::TWO_PI * ((float(-1*value) / float(_Joystick->MAX_AXIS) + 1.0f)/2.0f)+Ogre::Math::HALF_PI;
```
The -1 in here is to reverse the axis value to let the direction of movement map better onto the perceived camera motion and the HALF_PI offset is just so that we start by facing the ogre model correctly. Finally, in the frameStarted callback you have to continue to update the camera position and orientation:
```
_Cam->setPosition(_myogrenode->getPosition()+Ogre::Vector3(20.0f*Ogre::Math::Cos(_camangle), 10.0f, 20.0f*Ogre::Math::Sin(_camangle)));
_Cam->lookAt(_myogrenode->getPosition());
```
Test to see if this works.