C o m b i n a t i o n o f T w o - a n d T h r e e -D i m e n s i o n a l S p a c efor Solid Modeling

Hayato Yoshimori
Masatoshi Matsumiya
Haruo Takemura
Naokazu Yokoya

This sketch describes a novel hybrid 3-D object modeling system, NIME-NAIST
Immersive Modeling Environment, which inherits the advantages of both traditional
2D GUI based interface and 3D immersive modeling environment (fig.1). Figure 2
illustrates the whole system.

Figure 1: A scene of modeling in NIME

Display

Ultrasonic SensorInertial Sensor
Graphics Work Station

Light Pen

Figure 2: System Configuration of NIME
By employing a slant rear-projection display, NIME integrates 2-D and 3-D modelingenvironments into a unified modeling space. On the surface of the display, NIME
provides a user 2D GUI modeling interface . NIME also provides the 3D modelingenvironment with a field sequential stereoscopic imaging of objects and 6-DOF
pen-type input device. Therefore, a user can create models seamlessly switching
between these two modeling environments.
Unlike the conventional 3D CG software systems, which display the projected images

of manipulation targets, NIME provides a user the 2D modeling environment byshowing the intersection of targets and the display surface on the screen. By showing
both stereoscopically displayed object and its intersection all the time, a user can create
objects seamlessly either in 2D or 3D modeling environments without any operation toswitch one modeling environment to another.

Figure3: Pen-type input device with 3 switches
A 6-DOF pen-type input device (fig. 3) is developed and used in this system. The
device is a combination of a light pen, an inertial sensor, and an ultrasonic sensor.
This pen-type input device can be used in both 2D and 3D modeling environments withthe 3 switches arranged at the tip and the side part. By calculating the distance
between display surface and the tip of the pen-type input device, NIME detects whichmodeling environment the user intends to use. When the distance is within 5 mm, theuser’s operation is considered as for the 2D modeling environment and a dot cursor isshown according to a series of input from the light pen. On the contrary, when thedistance is beyond 5 mm, it is considered as for the 3D modeling environment and anarrowhead cursor is shown according to a series of input from the inertial sensor andthe ultrasonic sensor.
In NIME, a user can perform a number of modeling operations in both 2D and 3D
environments according to the nature of each operation. To create objects, first a user
makes 2D plane shape in 2D modeling environment. After creating 2D shape, a user
can extrude the 2D shape directly into 3D space. We call this way of creating objects“direct extrude”. Once a user extrudes the 2D shape, the intersection of the object
becomes to be possible to edit. Fig.4 shows the process of “direct extrude”; (a) arectangle is created in 2D modeling environment, (b) the rectangle becomes aparallelepiped by “direct extrude”, (c) the intersection is edited and (d) “direct extrude”
is done again.

(a)

(b)

(c)

(d)

Figure 4: A process of “direct extrude”
Three moretypes of shape creation are prepared. They are path-extruded,

revolving and pyramidal shapes(Fig. 5).

Figure 5: Three prepared shapes and the referential objects”
Same as “direct extrude”, first a user creates 2D plane shape. After that a user specifies
which types of shape a user wants to create through the buttons on the surface of thedisplay, an referential object that correspond to the specified shape appears. The
referential object is a extrude path of path-extruded(A), the axis of rotation ofrevolving(B), or the summit point of pyramidal shapes(C). Users can always edit thereferential objects during creation of each object, and at the same time, the original 2D
plane shape can be edited. Users can confirm the effects of the change to the referential
object and the original 2D plane shape immediately in 3D modeling environment
stereoscopically.
To modify the created objects, NIME offers 4 types of operations to users, that is“extrude the intersection”, “edit points”, “virtual magnet” and “Boolean operation”.
By using “extrude the intersection”, users can modify the object as shown in figure 6.

Figure 6: A process of “extrude the intersection”

The sphere is arranged so that the bottom part will intersect with the surface of thedisplay. After pushing button of “extrude the intersection”, a user can extrude theintersection by translating the object in 3D space. Same as the “direct extrude”, theintersection is possible to edit. Finally, to make the intersection the base, a user push
the button again.
Users can move the selected points of object both in 2D and 3D modelingenvironments. When users move the pen-type input device in 2D modelingenvironment, the selected points translate only the 2D direction. When in 3D modelingenvironment, the selected points translate 3D direction freely.

Figure 7: A process of “virtual magnet”
The“virtual magnet” is used when a user wants to give the object smoothgradation(Fig. 7). When a user selects “virtual magnet”, the arrowhead of the cursor
changes spherical head, which shows the area of influence of “virtual magnet”. A user
can modify the object by moving the pen-type input device.
The “Boolean operation” is implemented to perform in 3-D modeling environment,
because it becomes easier by giving users ability to understand the relationshipbetween objects and to move objects with 6 degrees of freedom.
Finally, the modeling process of an apple is shown in figure 8.

(a)

(b)

(c)

(d)

(e)

(f)

Figure 8: A process of modeling an apple

a) First, the 2D plane shape, which is the cross section of an apple, is created in
2D modeling environment.
b) By revolving the 2D plane shape, the body of an apple is created.
c) The “virtual magnet” is performed to give the body some natural distortion.
d) A reef is created as 2D plane shape and bended by “virtual magnet”.
e) Beginning with a circle, repeatedly applying “direct extrude” and editing theintersection create a stem.
f)

To apply “Boolean operation”, each object is arranged at appropriate position.

Figure 9 shows the rendered image of the apple created in NIME.

Figure 9: A photo-realistic rendered apple