網格(Mesh)廣泛應用於遊戲或者電影動畫製作等各種應用之中。並且為了追求真實感，許多網格會透過3D掃描重建的方式來建立。3D掃描重建需要利用專業儀器偵測並分析現實世界中物體的形狀、顏色、表面反照率等外觀資料，將其轉換成以離散形式表示物體表面的點雲(Point Cloud)，並再透過頂點的法向量等相關資訊去分析頂點與頂點之間的連接關係，將點雲重建成為3D網格。獲得3D網格之後，我們還需要為3D網格建立3D立體與2D平面的投影關係，再利用掃描獲得的彩色資訊為3D網格建立2D平面貼圖，並對2D貼圖進行優化。至此才能完成一個完整的3D掃描重建。然而掃描獲得的深度資訊並非都在統一的全局空間下，需要透過對齊將所有深度資訊獲得的點雲整合到同一空間中。這步驟稱之為點雲對齊(Point Cloud Registration)。

點雲對齊為3D掃描重建上的一個經典議題，而點雲對齊演算法又以最近點迭代演算法(Iterative Closest Point)\cite{ICPObjective}為主。但該演算法需要手動輔助以避免收斂後落入區域最小值。為了解決上述問題，本文針對環繞式掃描的情況，提出了一種可以減少誤差放大的自動點雲對齊演算法Group ICP，以及一種點雲對齊結果的評量方式。我們還提出了一種使用Group ICP的3D網格重建系統，完整地建制從掃描到建制含貼圖的網格。並在與市面上其他掃描重建系統的比較中獲得更加優秀的成績。

Mesh is widely used in various applications such as game or movie animation production.
In order to pursue realism, many meshes be created through 3D scanning. reconstruction.
3D scanning reconstruction requires the use of professional equipments to detect and analyze the appearance data such as the shape and color of the object or environment in the real world, albedo rate, and so on.
Point cloud is a representation of discrete data obtained by this method, and then use it to calculate the connection relationship between the vertex and the vertex by the normal and other related information of the vertex, and finally reconstruct the point cloud into a 3D mesh.
After obtaining the 3D mesh, we also need to establish the projection between 3D to 2D for the mesh, and use the color information obtained by scanning to create a 2D texture for the 3D mesh, and then optimize the 2D texture.

Point cloud registration is a fundamental problem in 3D model reconstruction, and it is mostly based on Iterative Closest Point(ICP)\cite{ICPObjective} which requires manual assistance to avoid falling into the local minimum.
We proposed an automatic point cloud registration algorithm "Group ICP" that can reduce error in the case of surround scanning.
Our system is an automatic point cloud registration method to reconstruct mesh from point cloud and reconstruct the texture form different view when scanning.
We also compare our system with commercial scanner and applications, and our result out stand for others.

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