Haptics – the science of touch. No other sense allows simultaneous transmission and reception of data. When you touch clay, you are truly interacting with it, feeling its description and manipulating its shape via tactile feedback – resistance, texture, volume, density, etc. Now think about working in your favorite 3D modeling application – using a conventional 2D mouse. Can you really say that a mouse delivers feedback? Does a trackball? Any 2D device? Of course not.

The Phantom Desktop, from SensAble Technologies, is a device that delivers real 3D manipulation of virtual objects via a stylus attached to an arm that moves at once in the x, y, and z planes. It fits your hand somewhat like an airbrush and has a single button that actuates specific control in the software, FreeForm, to carve, build, or otherwise change your "digital clay" surface. You can push, pull, move laterally, vertically and rotate the stylus to control your 3D cursor very intuitively.

The base is a nice, hefty, solidly cast metal platform with a relatively small footprint – about the same size as a mouse pad – and the stylus/arm mechanism is light high-impact plastic and free of turbulence in its motion. The practical range of motion is quite impressive, and it is easy to work within the envelope that’s provided -- after only a few minutes of practice. The unit is quiet and smooth in its feedback (more on this in a minute), but like any fine instrument, if you tried hard enough, I’m sure you could break it. It connects to your machine via bi-directional parallel port, and is powered with a DC adapter, making setup a typically painless process. If conflicts arise with dongles/peripherals attached to the parallel port, one can simply get an inexpensive PCI parallel interface and configure accordingly.

Inside the housing is a proprietary motorized cable and pulley system that uses precise sensors to calculate the position of the arm applying the appropriate amount of force-feedback in relation to the cursor’s position in space. The feeling you get when you first pick up the stylus is uncanny; it is hard to believe that such an aparatus could behave this way. You can actually feel the size, shape, texture, and location of objects in space! You can probe the cursor along the top, sides, even inside your shapes, all the while feeling resistance that approximates a real object. While it looks more along the lines of a Star Wars-type droid appendage, it sure feels like something from Cronenberg’s eXistenZ – a muscular little biomechanical creature… It feels, in a word – organic.

Carving out a niche: The sphere-shaped cursor pushing through "virtual clay."

This is exactly the kind of thing you would expect from the combined vision of the Phantom’s creators, who met at MIT – Thomas Massie was an undergraduate interested in robotics, when he met Dr. Kenneth Salsbury of the Artificial Intelligence Laboratory. Together they would design and develop the Phantom, ultimately forming SensAble and incorporating in 1993.

Since that time, both the Phantom and its software counterparts have been refined into two main commercial solutions: The Ghost SDK (software developer’s kit) – and the FreeForm modeler. The Ghost SDK provides programmers with a standardized format for translating data from the Phantom into their applications, optimizing the speed at which these applications can be written and freeing the programmer from having to "discover" the inrticacies of robotics I/O.

FreeForm is the way that most of us will relate to the Phantom, however, as it was designed to be a truly accessable means for visualization, modeling, and design. Some of you might remember the Phantom and FreeForm from SIGGRAPH ’99, where open clinics were offered for attendees. It was a big hit with traditional and 3D artists - and especially folks who didn’t know they could sculpt!

The interface of FreeForm is a large window with a toolbar running down one side and drop-down menu along the top. Speed in navigating the interface can be achieved by utilizing a combination of mouse, Phantom movements, and keyboard shortcuts. Since the interface is deliberately simple, the learning curve is quite manageable, with most common functions only a few motions away. You may start with a primitive shape, or empty workspace, and fill or carve from there. Typically you would start with a soft clay setting and rough texture. Doing this makes your preliminary work quick highly interactive, as you are not rendering millions of polygons to the screen – yet. As you refine your shape, you can progressively harden the clay and increase detail (polygons) in areas that warrant special attention.

The basic modeling tools are a sphere, cube, cylinder, and two specialty shapes that function sort of like pallette knives. These tools can operate in three different modes, affecting material in three dimensions respective to the shape of the tool: A carving mode that removes clay, a buiding mode that creates clay anywhere in the work area, and a augmentation mode that builds clay from the surface of an existing shape. Getting the hang of which tool to use for a given task is pretty quick and enjoyable. Experimentation is vastly rewarded! Maneuvering the model (grabbing it and repositioning) is almost as exciting as creating shapes – you get really fast with rotating your clay and zooming in to look at your detail areas.

There are other features that, like modeling with foam or clay, have particular applications and speed up the process. Wire Cut allows one to carve/add to shapes by drawing on a template initiating a Boolean operation. This is very handy, but can be tricky at times, depending on your design habits (more on this in a moment). Mirror allows you to place a plane anywhere on your object that will "reflect" the given side, making modeling symmetrical objects fast and easy. There’s a facility to create slices of an object, a measurement tool, and an extremely useful 3D selector that you can use to cut and paste sections of your work.

20 minutes of work in FreeForm = A roughed-out ’32 Ford.

Only a few things about FreeForm felt kludgy: In Wire Cut, I’d like to see an easier, more fluid way of doing vector operations like with Adobe Illustrator, and to be able to turn off the tactile "snap-to" feature. Compatibility suffers a bit for the moment, as there isn’t a provided translator to the common animation file formats, however, third-party applications, can accomplish this. And, it would be soooo great to be able to paint and add texture maps in 3D with the Phantom… A development like this would make it pretty unstoppable in the market, even lacking the ability to animate. Adjustable levels of undo (there are a maximum of 6 undos possible) or a sequential autosave would be nice too.

Overall, though, the hardware/software combination really rewards the user over a conventional 2D setup. In a short amount of time, a user can learn the interface, adjust to the stylus, and become quite adept at modeling with the SensAble products. I can’t stress enough the value of the freedom to explore the process of modeling, rather that learning how to navigate menus and setting parameters.

In stitches: Using the Phantom to guide a virtual hemostat.

In alternate applications, the Phantom device also shows great promise: In combination with a 3D printing device, it becomes an excellent way for engineers and industrial designers to proof parts before machining them. As a precision guidance interface, it could conceivably aid in unmanned vessels retrieving objects from the ocean floor (or Mars), or a bomb squad remotely checking suspicious packages by robot. In the realm of medicine, there are those who are applying Phantom technology to help the vision-impaired, and still others who are investigating its’ use in virtual surgery. There is also progress toward a Gibsonian promise of Cyberspace, an immersive object-based computing environment, for example, where one could interact with speed and utility not afforded the 2D desktop.

The Phantom with FreeForm costs about $15,000, and requires dual Pentium II (300Mhz or better) processors, 512MB of RAM, 68MB of disk space, an OpenGL graphics card with a minimum of 32MB of onboard RAM, and a display capable of 1024x768 (or better) resolution. Our results were due in no small part to the use of a robust Intergraph TDZ 2000 GL1 workstation with a Wildcat card, so I would recommend adherence to the requirements!