Designing a New Toy to Fit Other Toy Pieces- A shape-matching toy design based on existing building blocks Yuki Igarashi∗
University of Tsukuba / JSPS Research Fellow(a) Building blocks(b) Input photograph(c) The user designs a toyusing a sketching interface

Hiromasa Suzuki
The University of Tokyo(d) Traced outlines(e) Block-shape matching toyFigure 1: Overview of our method

1

Introduction

Shape-matching toys are popular items for infants, and consist ofboxes with many holes in different shapes along with corresponding blocks of the same shapes. To play with the toy, an infant finds
and inserts a block matching the shape of a particular hole. It is difficult to design new shape-matching toys based on existing blocks.
We assume that the user performs such design as shown in Fig. 1(e) based on existing building blocks like those shown in Fig. 1(a). The construction of the toy body can be roughly divided into
three steps: gather the parts, lay them out on a wooden board andtrace them using a pencil, and saw the wooden board. This manual method is straightforward, but errors cannot be rectified and it
is also unsuitable for mass production. Accordingly, we propose
the use of a laser cutter (e.g., Commax Laser System) or a cutting
plotter (e.g., Craft ROBO). Today, services are available that allow
the user to send a vector dataset to a company and have the corresponding wooden board returned to them.
We propose a computer-based method for novices to enable the design of a new toy to fit another existing toy. The method involves
designing a construction diagram for new toy on a photograph ofthe existing toy using a computer (Fig. 1 b). The user first takes aphotograph of the existing toy on a checkerboard, then designs theform of the new toy on the photograph using a sketching interface.
To take the photograph on the checkerboard, the system automatically fits the designed toy to the real measurements and exports theresults in vector form. The system supports SVG and DXF formats.
Finally, the user cuts the shapes from a real wooden board using acutter plotter or laser printer.

2System Overview

Figure 1 shows a real toy made using the proposed method. Our
goal is to design a new shape-matching toy (Fig. 1 e) from existingbuilding blocks (Fig. 1 a). The user first prints a checkerboard andtakes a photograph of the existing building blocks Oexisting on it.
The user draws free-form strokes on the input photograph shapes(line, rectangle and ellipse), and exports the user-input strokes invector form as shown Fig. 1(d).
The checkerboard is used for scale adjustment. Although various
methods have been proposed for feature point extraction in 2D[Carlson 1988; Bradski and Kaehler 2008], no method currently
enables precise extraction. Accordingly, we adopt manual input by
the user. The system first extracts the grid of the checkerboard, andthe user can easily mark the corners of the grid using the extractededge detection image (Fig. 2 c). The user has to mark corners at∗ e-mail:yukim@acm.org

more than two unbroken points (Fig. 2 b). The system then calculates the ratio of the image to the actual size. We applied the method
to the design of a new toy using existing real toys (Fig. 1 and 2).

(a) Existing puzzle(b) Designed the puzzle cover shape(c) Edge detection image(d) The resulting real puzzle cover

Figure 2: Example of a puzzle cover design based on an existingpuzzleUser3 (Illustrator)

Photo capture
DesignMarking
Measurement
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User2 (our method)
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Figure 3: Comparison of timing data

3 Evaluation
We tried the system with three test-users who designed a shapematching toy as shown in Fig.1. Figure 3 shows a comparisonof our method and existing software (Adobe Illustrator). In ourmethod, the user first takes a photograph of the building blocks
on a checkerboard, then draws strokes to create a diagram for theshape-matching toy on the photograph and marks its corners. In
the existing method, the user first measures the building blocks anddraws a construction diagram for the shape-matching toy. It is only
necessary to mark 5 − 6 points from the results of the user study.
It took about 10 − 13 seconds, and the test users reported that theyfound the system easy to use.

References
B RADSKI , G., AND K AEHLER , A., 2008. Learning openCV: Computer vision with the openCV library.
C ARLSON , S. 1988. Sketch-based image coding of gray-level images. Signal Processing 15, 57 – 83.