Development of a simulation system of combination blocks for educating kids about three-dimensional modeling.

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In this research, we developed edutainment software for teaching kids the basis of 3D modeling in virtual space. The modeling system simulates combination toy blocks. Each of the blocks can be united with another blocks by 6 directions ; up, down, right, left, front, and back.In operations for jointing blocks correctly, collision detection requires highest computing cost. At the first version, we limited shape of blocks to the combination of the unit cubes. By dividing 3D space into the unit cubes, cost of the collision detection was much reduced. Then view rotation interface that uses a track ball was added in order to control both object position and eye position at the same time.At the next version, surfaces of blocks were defined with triangles like a general CG system, in order to display curved blocks such as arcs and circles. And a tree of oriented bounding box (OBB) was added to each block. By judging overlap of the OBB trees before judging collision of blocks, fast collision detection was achieved.In the real world, kids combine and separate toy blocks by cooperatively moving both hands. However, the both hands operation had to be replaced a set of one hand operations, since the previous systems have only one mouse. Thus, we developed double mice interface to simulate the both hands manipulation.In addition, we contrived an algorithm for dividing an agglomerate of blocks to two parts using the two mice. The algorithm, at first, creates a separation plane at the center of two blocks each of which was selected by a related mouse. Then, at each side of the plane, blocks both directly and indirectly connecting to the selected block are gathered to a group. Finally, remaining blocks, which do not connect to the selected block of the same side, are merged to the group of the opposite side. This algorithm is in implementation.