Joystick Support

As of version 1.10, Panda3D gained built-in support for various input devices including but not limited to joysticks, gamepads and steering wheels.

We’ll be starting with a little bit of theory to get you some knowledge of the underlying system to be able to understand how gamepad support works. The support for devices is given through evdev, the joystick api or xinput dependent on the OS you are using. Hence all devices that are recognized by your system will be available by the engine. Each connected device will be classified by one of the following device classes:

# It is not known what type of device this is.
unknown

# This means that the device doesn't correspond to a physical
# device, but rather to a dynamic source of input events.
virtual_device

# A physical, alphabetical keyboard.
keyboard
mouse
touch

# A gamepad with action buttons, a D-pad, and thumbsticks.
gamepad

flight_stick
steering_wheel
dance_pad

# Head-mounted display.
hmd

# 3D mouse, such as produced by 3Dconnexion.
spatial_mouse

These DC’s are stored within the InputDevice.DeviceClass enum which can be imported from panda3d.core.

Note

Linux users may need to be in the “input” user group to get access to the full range of available device functionality.

Buttons

Just like the already existing keyboard support, you can catch button events of each device connected to your system. Unlike keyboard button events, each device will send its button events with a specific prefix. These prefixes need to be set by the developer when a device is attached for usage, which can be done with a call to self.attachInputDevice(device, prefix="[your-prefix]"). The device that needs to be passed to this function can be obtained using self.devices.get_devices(), which will give you all devices of a given device class. After the device has been attached, you can catch events like for example, "[prefix]-face_a" which will be thrown whenever the ‘A’ button on the device with the specified prefix is hit. As with keyboard support, there also is the ‘-up’ postfix which can be added to catch the event which will be thrown when a previously pressed button is released again. Note, if a button with an to the engine unknown code was pressed, an event like the following will be thrown. "[prefix]-none"

In addition to events, you can also check for specific buttons to be pressed with the find_button() method of a device object.

Here we’ll check for the right thumbstick to be pressed

gamepad = base.devices.getDevices(InputDevice.DeviceClass.gamepad)[0]
right_stick = gamepad.findButton("rstick")
if right_stick.pressed:
    # Do whatever you want when this button is pressed

If you want to check which events are thrown on specific device input, you can set the following config variable for debugging. notify-level-device debug

Alternatively you can also add this line somewhere in your application

messenger.toggleVerbose()

Axes

The above mechanism works well for digital buttons, which can only be in an on or off state. Many game controllers also have analog controls, often referred to as “axes”, which can have a variable value. In Panda3D, these values will be 0.0 when the respective control is in its default or resting position, and 1.0 when it is in its maximum position. Some controls can move in two directions, and can have a value of down to -1.0.

This sample will show how to get the left analog stick of the first gamepad device

gamepad = base.devices.getDevices(InputDevice.DeviceClass.gamepad)[0]
left_x = gamepad.findAxis(InputDevice.Axis.left_x)

# Access and use the value for whatever you need it
left_x.value

With the find_axis() method we tell the device which axis we are interested in and finally get the axis value using the value member. The state member will give you a double precision representation of the control’s current position and should be called within a task method to get a constant update of the controls position changes if desired. It sometimes is also prudent to store the centered position of each control early in an application to simplify the calculation of the distance the control has been moved in any direction. Some applications and devices also do this automatically in a given idle time or provide the user a dedicated re-calibrate action.

Note

find_axis() will return a dummy object if the axis doesn’t exist. You can check for the boolean value of the returned object (ie. if left_x:) to see if the returned axis has a known value.