User Interfaces- FreeForm Modeling

1 Apr, 2001 By: Joe Greco

Joe Greco

User Interfaces- FreeForm Modeling

The FreeForm Modeling System from SensAble Technologies is a device that employs a haptic interface. This means that the sense of touch plays a key role in the user’s interaction with virtual objects. I had a chance to spend some time with the system and found it to be a strong candidate for this month’s column.

How it Works

Figure 1. The FreeForm Modeling System uses a stylus-type device, which provides forced feedback when the virtual model is contacted. Here, a virtual coffee maker is being sculpted.
Figure 2. This starter block of clay comes complete with all the subtle detail of real clay, such as rounded corners.
Figure 3. The Carve with Ball and Carve with Scrapper tool made these two distinct cutouts on the digital clay.
Figure 4. The Tug tool is one of the most powerful for making large-scale edits, as this embossment and indentation show.
Figure 5. Setting up workplanes in the FreeForm software is very intuitive.
Figure 6. The complete loft. In the upper left-hand corner is the Object List box showing the various planes and options available by right clicking.
Figure 7. The Carve and Smooth tols were heavily used to shape the mouse's form.
Figure 8.The dialog box for changing the coarseness of the clay is intutive.
Figure 9. At the top front of the mouse, the 2D curve that will determine the groove for the buttons is created.
Figure 10. With the Carve tool set to a large amount, I reduced the size of my mouse. I could have also used the 3D select tool to select the unwanted area and deleted it.
Figure 11.The FreeForm software has an amazing smoothing routine. This is the same side as Figure 10, after the amazing SMOOTH tool was applied
Figure 12. The mouse with the last details added.

Instead of forming clay with your hands and then using a 3D input device such as a touch probe or laser scanner to create a 3D model, the FreeForm Modeling System allows for the shaping of virtual clay in physical space. The hardware component of the system is called the Phantom Desktop, appropriately named as it takes up a space of only about 6 by 6 inches. The Phantom applies resistance to a stylus-like device connected to the unit via a swing arm. The stylus and arm combine to produce a full six degrees of freedom. When you probe at a virtual model with the stylus, the Phantom recognizes when contact is made and provides force feedback, thereby giving the sense that you have come in contact with a physical model, as shown in Figure 1. The stylus’ movements are mapped to the computer screen and displayed in a software program, also called FreeForm, along with the virtual model being sculpted. Essentially, you are using a physical device to make a virtual model.
The Phantom stylus is usually held in the right hand and the computer mouse in the left (assuming you are right-handed). The mouse is still a critical element as it’s used to select tools in the FreeForm software. For example, one tool may act as a putty knife, while another may push and pull material. The mouse is also used as a navigation device as the buttons, from left to right, rotate, pan and zoom, which makes these operations very intuitive.


The first state-of-the-art aspect of the FreeForm Modeling System is how easy it is to set up. The device went from being sealed in the medium-sized box it came in to on my desk with me sculpting 3D forms in about 30 minutes. The key to this speedy transition comes from not needing to set up complex origins, coordinates and xyz planes. When the FreeFrom software is launched for the first time, a default rectangular block of virtual clay is made available on screen, as shown in Figure 2, and the Phantom automatically senses where this block is in 3D space.

A rectangular border that indicates the extents of the workspace frames this starter “clay.” The clay can’t be “pushed” outside of this area, but the stylus can be moved past this boundary, which can be enlarged if need be. I did notice that on certain models oriented in a particular view, the stylus would interfere with the Phantom, thus restricting movement.

The second tool, used to carve the clay, is already selected. With this tool, or any tool for that matter, the stylus can be passed over the clay with resistance felt everywhere there is contact in the virtual world. In order to get the Carve tool to perform its task, a small button on the stylus is depressed, and then the fun begins.

The Carve tool pops out to reveal five other variations, the effect of a few can be seen in Figure 3. Not only does the software’s editing tools respond to the direction that the virtual tool is facing, but also to the amount of pressure placed against the clay. This effect is similar to Photoshop’s or Painter’s pressure sensitive brush tools, only in 3D.

There are a host of other tools for smoothing and smudging the clay, and most tools have sliders for adjusting the size of the tool and the amount of smoothness. Another tool adds balls of clay, either connected or independent of the main mass, at the desired size. One of the most powerful tools is the Tug, which allows you to push and pull the virtual clay around, as shown in Figure 4. There is also a Mirror tool for creating symmetrical models, and the software features multiple Undos, thus encouraging creative experimentation.

The developers have centered much attention on the details of how the tools work. For example, when you select a tool such as Carve, the cursor not only changes to match the icon of the tool, but it also becomes transparent, making it easy to see through and to get a better idea of what is going on.

Building a Mouse

After I got a feel for most of the tools, I decided to create an actual object—a computer mouse. I figured that the best way to start was with a blank slate rather than trying to carve away at a large lump of clay. I picked the New Plane tool, and the software created an initial plane in the front face of my boundary area. By hitting the same icon again, another plane was created in the same location, and, by simply using the phantom stylus with its button depressed I was able to grab it and move it to the back face of the work area, as illustrated in Figure 5. By clicking in other areas of the plane, I could have scaled or rotated it—this latter action is particularly interesting as the rotation of the stylus rotates the plane.

After I created a third (middle) plane, it was time to create the 2D profiles that I would loft into the basic shape of the mouse. The 2D-sketch environment, which has been enhanced with the recent introduction of Version 3 of the FreeForm software, features a simple but handy array of arcs, lines, splines and so on. While it is a little tricky to get used to drawing with the Phantom’s stylus, (this is not as natural as the earlier 3D clay editing operations), snapping to endpoints is as with no other software I have ever used because you can actually feel FreeForm pull you toward the point. Moving and resizing the 2D entities is fairly simple.

With the three profiles created, I picked the Loft tool, selected each one and used the Add Material option, to produce the results shown in Figure 6. If I already had material, I could have cut away at it using the same Loft tool. Profiles can also be revolved, used as a wire to cut through the model or turned into a boss or groove. One minor limitation that, in some cases, adds extra steps is that all profiles have to be closed, but the system lets you know if this is the case by showing an open profile in red, while a closed one is blue.

Design Development

Using basically the Carve and Smooth tools, I was able to sculpt the original loft to what is displayed in Figure 7. As the rough model starts to take form, the coarseness of the clay can be upgraded, and the first step up is from Rough to Refine Shape, as shown in Figure 8. In doing so, this changes the appearance of the model, making it look a lot smoother. The key is not to add too much detail in the Rough stages. For example, tools such the Groove mentioned earlier seem better suited for applying with finer clay coarseness. After Refine Shape, there are two higher levels of detail you can progress to—Add Detail and Add Refined Detail.

Design Detail

In order to create features such as grooves, the sketch environment must be entered and a 2D profile created. It would be nice if FreeForm came with a few standard groove profiles such as V-grooves, U-grooves and so on. In any case, after drawing the notch, by evoking the Groove tool, the software asks you to locate the profile and then draw a curve that delineates its path, as shown in Figure 9.

After adding the groove, which determined the location of the mouse buttons, I realized the device was too large, so I used the Carve tool and wiped out about one-third of the back of the mouse, which resulted in what is shown in Figure 10. Even though the model looks as though I just ripped off a chunk of clay, by using the amazing Smooth tool with a large diameter setting, I was able to fix it, as shown in Figure 11, in only a few minutes.

To finish up, I added another groove and did some additional smoothing, which is shown in Figure 12. Finally, I exported the model as an STL file and tested this file in Rhino with good results. The program creates a lot of polygons, so there is a decimator utility that reduces the number of points in an STL file. It also has options to export slices that generate profile curves at the specified interval. In addition, a scanned image can be brought in as a BMP file and either traced over with the drawing tools or used as an embossment.


New to Version 3 is the introduction of surfacing commands. The FreeFrom software allows users to outline surface areas and create patches. These patches can then be output as an IGES file for further work in an MCAD program. A popular use of the FreeForm Modeling System is to sculpt the exterior of a consumer product, such as the coffee maker shown in Figure 1, and then use a CAD product to design all the inner workings.


The FreeForm Modeling System is absolutely state-of-the-art because it gives designers a new level of creativity that is not possible with other input devices. While it can’t be used to design the gears and mechanisms that make up traditional MCAD, for CAID(computer-aided industrial design) it is a device that no designer should be without. However, the $25,000 price tag, along with a computer that houses dual 1GHz processors and 512MB memory (recommended configuration) will prevent many users from getting one. If you do save your pennies, it would be money well spent.

About the Author: Joe Greco

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