樂高®積木自1940年代發展至今，已成為廣受歡迎的積木玩具，在電腦計算領域中，也已有許多研究描述如何利用樂高建構指定的二維圖形或三維模型；然而，這些研究大多以具長方體狀的樂高基本磚為構成單位，導致結果外觀上具有像素或體素風格。本研究透過在構成單位中加入不同尺寸的斜面磚，改善樂高表面的平滑程度，在確保結果符合目標形狀的情況下，建構出具平滑外觀的二維樂高結構。由於加入不同形狀及尺寸的斜面磚，導致建構過程中需額外處理目標與結果外觀的相似度，我們引入位勢場的概念，透過計算目標與結果的邊界距離和形狀變化，判斷樂高與目標圖形間的相似度，作為建構樂高磚選擇的依據。由於加入多種外形、尺寸的樂高磚，導致無法透過窮舉法找出最佳的建構組合，我們使用疊代策略，在每次疊代中選擇提升最大相似度的樂高磚，在可行的時間內建構出結果；最後利用樂高基本磚增加內部結構的穩定性。在結果中，我們輸入多種類型的二維圖形，驗證在不同情形下方法的效果、穩定性及擴充性。

Lego® has been developed and well-known since 1940s. In computer science, it has been studies that describing the procedure to automatically generate Lego sculpture, including 2D and 3D. However, these studies mostly only consider basic Lego brick, which has cuboid appearance, as constructing component. As a result, the generated Lego sculpture appears pixelized or voxelized. We propose a method to improves the smoothness of the contour of 2D Lego sculpture by adding smooth Lego parts, including different shape and size. Due to the expansion of constructing component, the considering of similarity between the Lego sculpture and input image during the constructing becomes necessary. We introduce the concept of using potential field to determine the similarity between Lego and image, by calculating the distance and the variation of contour between Lego and image. Variable shape and size of Lego parts leads the possible combination of Lego sculpture growing exponentially. It is impossible to find an optimal solution of combination in polynomial time by brutal force. We use an iterative strategy to generate an approximate solution. Choosing the brick that maximally increases the similarity in every round of iteration. For internal area of contour, we using basic brick to increase the stability of Lego structure. Finally, we using variable image as input to examine the efficiency, stability and scalability of our method.

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