基於質量彈簧系統的網籠形變複製

Cage-Based Deformation Transfer Using Mass-Spring System

董晉嘉(Chin-Chia Tung)

指導教授 ： 歐陽明

國立臺灣大學/電機資訊學院/資訊工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.00823

摘要

本論文提出了一個基於網籠形變(Cage-Based Deformation)輔以質量彈簧系統(Mass-Spring System)的形變複製(Deformation Transfer)。根據來源模型建出包覆住它的網籠，之後調整來源模型的網籠使它對應到目標模型的網籠。使得來源模型以及目標模型的網籠具有一致性，意即他們之間的頂點、邊、三角形是一對一對應的。有了一致性的網籠之後，在網籠上建立質量彈簧系統，結構根據來源及目標模型的網籠，每個頂點對應到質量點，頂點與頂點間的邊則對應到彈簧。根據來源網籠的原形對應的質量彈簧系統，以及形變後的網籠結構對應的質量彈簧系統，計算出每條彈簧的延展比例，並把延展比例套在目標網籠每一條對應的彈簧上，使得目標網籠的質量彈簧系統上每條彈簧的靜止長度做對應的改變，根據虎克定律計算出目標網籠的靜止平衡狀態。最後根據目標形變後的網籠結構，透過座標系統內插計算出目標模型經過形變後的外觀。使用質量彈簧系統使得形變轉移得以考慮物理因素進去，在某些例子下可以產生比之前方法更合乎物理的結果。而使用基於網籠的形變則可以有效減少因為完全用質量彈簧系統計算複雜模型網格而導致外觀結果可能塌陷的不穩定的因素。

關鍵字

Deformation transfer ； cage-based deformation ； mass-spring system

並列摘要

In this thesis we propose a method for deformation transfer. Given a source reference model and its deformed model, we want to compute the deformation of a target reference model. We construct a cage which encloses the source reference model, and construct the correspondence between the cage and those of the source deformed model and the target reference model to guarantee these three cages have same topology. Each cage is associated with a mass-spring system, and then the spring stretchiness ratios between the source reference cage and the source deformed cage are applied to the target reference cage. After computing the equilibrium state from spring stretchiness configuration of the target mass spring system, we get the deformed cage of the target model. Finally, we use the target deformed cage to reconstruct the target deformed model by vertex coordinate interpolation. Using mass-spring systems allows us to take physical effects into consideration when performing deformation transfer, and combining with cage-based deformation method alleviates the artifact of collapsed surface caused by mass-spring systems and makes the result more stable.

並列關鍵字

形變複製 ； 網籠形變 ； 質量彈簧系統

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