User Interfaces- FreeForm Modeling
31 Mar, 2001 By: Joe GrecoJoe Greco
User Interfaces- FreeForm Modeling
The FreeForm Modeling System from SensAble Technologies www.sensable.com is a device that employs a haptic interface. This means that the sense of touch plays a key role in the users 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 months column.
How it Works
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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. |
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Figure 2. This starter block of clay comes complete with all the subtle detail of real clay, such as rounded corners. |
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Figure 3. The Carve with Ball and Carve with Scrapper tool made these two distinct cutouts on the digital clay. |
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Figure 4. The Tug tool is one of the most powerful for making large-scale edits, as this embossment and indentation show. |
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Figure 5. Setting up workplanes in the FreeForm software is very intuitive. |
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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. |
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Figure 7. The Carve and Smooth tols were heavily used to shape the mouse's form. |
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Figure 8.The dialog box for changing the coarseness of the clay is intutive. |
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Figure 9. At the top front of the mouse, the 2D curve that will determine the groove for the buttons is created. |
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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. |
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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 |
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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 its 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.
Setup
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 cant 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 softwares 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 Photoshops
or Painters 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 objecta 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
itthis 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 Phantoms 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 toAdd 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.
Surfaces
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.
Conclusion
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 cant 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.
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