From: owner-3dui@hitl.washington.edu on behalf of Doug Bowman
[bowman@vt.edu]
Sent: Tuesday, December 12, 2000 3:03 PM
To: 3dui List
Subject: description of an IT

Greetings!

I see that no one was brave enough to accept my challenge to
describe your favorite interaction technique. So, I thought
I would give it a shot. Here's a description of the Go-Go technique
(only the selection part, not manipulation).

Remember that my goal here is for this to be understandable,
yet precise.

---------------------------------------------------------------------
// declarations and definitions
constant GOGOTHRESHOLD = 0.3 meters;

object headTracker;
object handTracker;
object virtualHand;
object selectableObjects[N];

3Dpoint headPosition;
3Dpoint handPosition;
3Dpoint virtualHandPosition;
3Dpoint torsoPoint;

float virtualHandDistance;
vector virtualHandVector;

// all of this should happen before every frame is rendered
headPosition = world coord. position of headTracker;
handPosition = world coord. position of handTracker;

// assuming y is the vertical axis
torsoPoint = (headPosition.x, headPosition.y - 0.5, headPosition.z)

if(distance(torsoPoint, handPosition) <= GOGOTHRESHOLD)
	then virtualHandPosition = handPosition;
	move(virtualHand, virtualHandPosition);

else
	virtualHandDistance = GoGoFunction(distance(torsoPoint, handPosition));
	virtualHandVector = handPosition - torsoPoint;
	normalize(virtualHandVector);
	virtualHandPosition = torsoPoint + (virtualHandVector *
virtualHandDistance);
	move(virtualHand, virtualHandPosition);

for i from 0 to N
	if(highlighted(selectableObjects[i])
		unhighlight(selectableObjects[i]);
	if(intersects(boundingBox(virtualHand), boundingBox(selectableObjects[i]))
		highlight(selectableObjects[i]);
---------------------------------------------------------------------
Thoughts and comments are welcome. Is this a good level of description?
What's missing? What details are irrelevant? I didn't include many
comments on purpose so that you could see if the description itself is
understandable.

Best,
Doug

--
Doug A. Bowman, Ph.D.          (540) 231-7537
Assistant Professor             bowman@vt.edu
Computer Science        www.cs.vt.edu/~bowman/
Virginia Tech