The Ygdrasil User's Guide

Using the CAVE and CAVE Simulator

The WAND

There are limitless possibilities for hardware interface devices in the CAVE, ranging from joysticks and buttons up to full body motion capture suits. The standard, basic interface device for most CAVEs is called a Wand - a controller with a joystick and three buttons, designed to be used with one hand like a pointer or remote control. The wand also contains a tracking sensor, to track the position and orientation of the user's hand as well as input through the buttons and joystick. It is designed to be something like a mouse, but with the ability to track motion in 3 dimensions instead of just 2.

Using the Wand

Using the wand often takes a little getting used to, even for seasoned videogame veterans. There is actually no fixed meaning for the joystick and buttons on the wand. The most common configuration is to use the buttons to interact with objects, simulating touching or grabbing in the same way that mouse buttons are used. The joystick is usually used for navigation, moving your viewpoint around within the virtual environment. Pushing the joystick forward and backwards moves you forward and backwards, and pushing it left or right makes you turn. The buttons on the wand are numbered 1 through 3, going from left to right, and can do different things in different worlds. The left button (button 1) is often the main one used for interacting, for things like grabbing or activating objects, hurling projectiles, etc.

Driving and Flying

In "Driving" mode you can move forward and backwards and turn left or right, while in "Flying" mode you can also move up and down. This is done by pointing the wand up or down, and pushing the joystick forward. In fact, the joystick does not always move "forward" - it actually moves you in the direction that the wand is pointing. Note that this feature relies on the angle of the wand, NOT its position. So, if you hold the wand high in the air but still have it aimed forwards, it moves you forwards, not up. You can also use this technique to sidestep, or "strafe" - point the wand left or right and push the joystick forward, and you'll move to the side without turning.

CAVE Simulator

The CAVE Simulator lets you test out CAVE programs on a regular desktop computer without the tracker, wand, etc. It uses the mouse and keyboard to simulate using the wand.

Running the CAVE simulator

Any CAVE program can run in either the simulator or in an actual CAVE without any modification. The way the program is displayed is controlled by a system configuration file, so the same program can run in full CAVE mode on one computer and in a simulator window on another computer.

The CAVE Simulator Display

the CAVE simulator displays the world as it would appear in the CAVE, with a few additional displays. When you run a program in the CAVE simulator, you'll see a white wireframe cube and a red circle in the middle, as well as the virtual world. The wireframe cube represents the physical walls of the CAVE, and the red circle represents your head within the physical space of the CAVE. You can also see a small red box that represents the wand. These two objects form a very rudimentary avatar representing the user in the CAVE. They only show up in the simulator, NOT in the full CAVE. If you want to create an avatar, you have to explicitly create objects to use for a body - otherwise, you are invisible.

CAVE Simulator Controls

In the simulator, you can use the mouse and keyboard to simulate movement in the physical space of the CAVE, walking within the 10x10 cube, moving your head and hands. You can also simulate the controls on the wand to move within the virtual space of the environment.

Simulator tracking controls:
    CTRL + mouse to move wand left,right,forward,backward
    SHIFT +mouse to move wand left,right,up,down
    ALT  +mouse to rotate wand
     < and > to roll wand

          arrow keys to move left/right/forward/backward
    SHIFT+arrow keys to move left/right/up/down
    ALT  +arrow keys to rotate or tilt head

    HOME to reset wand in front of you
    P key to reset head and wand

Simulator wand controls:
    mouse buttons control wand buttons.  
    Left button = button 1, middle= button 2, right = button 3.
    SPACE+mouse to control joystick.  
    Without clicking, just move the mouse around the window.  
    When the mouse is close to the top of the window, you go forward.
    When the mouse is close to the left side, you turn left.  
    When the mouse is at the center, you don't move at all.

Simulator display controls:
    0  for wall view
    1  for perspective view
    2  for outside view
    W to toggle wand display
    U to toggle user (head) display
    INSERT to toggle CAVE outline
    DEL to toggle blackout of right, back, and ceiling walls
    keypad arrows (2/4/6/8) to rotate outside view
    keypad +/- to zoom outside view
    keypad 5 to reset outside view

    D  for Desk mode (for outline & blackout)
    C  for CAVE mode (for outline & blackout)

Navigation in the CAVE takes some practice, and navigation in the CAVE simulator also takes some practice. The controls in the CAVE simulator particularly are not the most intuitive, and are a bit cumbersome compared to the the controls in games or most 3D animation programs. This is because the simulator mode is not really the viewing environment for Ygdrasil, it's just a way to get a quick rough draft view of the scene.

In the simulator, the "outside view" or "god view" (2) lets you see from outside the user viewpoint in the CAVE. this is very handy for getting a look at the big picture of your world, and for seeing yourself in an "out of body" view to observe how interactions work. Note that the outside view ONLY exists in the CAVE simulator, for debugging purposes - it is NOT available in the full CAVE.

Example: CrayoLand Demo

To practice navigating in the CAVE, try the CrayoLand demo.

$ cd /usr/local/CAVE/demos/crayoland
$ ./cray

(c) Ben Chang