د/ايمان زغلول قاسم

استاذ تكنولوجيا التعليم المساعد بكلية التربية بالزلفي

presentations

Design and Generation of Primitive
Representations
Since the message surfaces are rendered in 3D, we also
prepare our primitive pieces in 3D, so that they can be used
to compose 3D Lego blocks quickly during the rendering
process. The following describes our method that allows
users to design the shapes of primitives by transforming 2D
images to 3D meshes.
Our method allows users to design their primitives using
gray-scale images, as shown in Fig. 4a. Instructors can use
any image editing software to input their design easily, and
the rest procedure is automatically handled by our method.
Specifically, we map a n  n (100 is used for all the examples
in this paper) grid on the input image, and preserve all the
line connections in the grid. The pixel colors (darkness
values) in the image are used to adjust the corresponding
point heights in the grid. This procedure generates an initial
3D mesh that matches the appearance of the input image. We
also use the point heights to separate the raised portions from
the background and assign them to different colors during
visualization. To improve the efficiency of the rendering
process, we simplify these meshes with the MeshLab
software [22] to generate the final primitive pieces. Fig. 4b
shows the generated mesh based on Fig. 4a and the
protruding surface is used to represent a sending operation.
We reverse the mesh in Fig. 4b to generate the receiving piece
with a dented surface. This design ensures that two content
surfaces can be put face-to-face if, and only if, their shapes
match. The content surface is then combined with the other
portions of a Lego block to generate the final results in Fig. 4d.
We have designed several Lego sets to cover all the
primitives in our selected uniform representation of
protocols, as shown in Fig. 5. These results demonstrate
that our approach can generate various Lego sets flexibly.
This method also allows other users to share these designs
and create their own shapes easily. We believe that the
ability to switch primitive designs can help users to choose
their desired styles and make the learning process more
attractive to students.
4.3 Generation of Content Surfaces
With the primitive pieces created above, we can automatically
generate the content surfaces of Lego blocks for a
given message. To compose a connected 3D mesh as the
content surface, we use the following procedure, which first
arranges a message content on a 2D table and then stitches
corresponding primitive pieces together.
A message often consists of a list of primitives connected
by manipulation operators such as encryption and concatenation.
We can view concatenation as the connection of
two or more primitives at the same level, and encryption as
the coverage of primitives at a deeper level. A 2D table can
be generated for any given message. For example, Fig. 6a
shows the filled 2D table for message “{B,{N_A,N_A}Ks_BS,
A}Ks_AS” in the Yahalom protocol. Starting from a corner
of the 2D table, we fill it with the message content by
increasing the row when seeing concatenation or increasing
the column when seeing encryption. We also record
whether or not a location on the table has content or not
by assigning a 0/1 flag to it. In this way, we can use such a
2D table to represent any message.
During the real-time rendering process, we draw Lego
blocks according to their content tables. For locations without
any content (with flag 0), we draw one big polygon to cover
the space. For locations with contents (with flag 1), we draw
the corresponding primitive pieces in the preassigned colors

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