摘要 |
An apex rhombus is delimited over the center point of a square, which is delimited by plotting four nadir rhombuses on the same plane, and each of the nadir rhombuses and the apex rhombus are jointed to form a group of pyramidal surfaces equipped with four planar slopes having substantially the same height in a pyramidal form. Two pyramidal surface slabs are assembled, each composed of pyramidal surfaces around one pyramidal surface, each sharing one nadir rhombus, adjacent each other, and arranged in a grid pattern at an equal pitch in plural directions. The pyramidal surfaces arranged in a grid pattern are each displaced by one-half pitch in a specific direction, such that the apex rhombus of one of the pyramidal surface comes in contact with the nadir rhombus of the other pyramidal surface, whereby the two pyramidal surfaces are placed one on the other.
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