在著色器中實作基於力學模型之虛擬塑形系統

Implementation of Mechanics-based Virtual Sculpturing System in Shader

曹廷群(Tsao,Ting Chun)

指導教授 ： 蔡宏營

國立清華大學/工學院/動力機械工程學系/碩士(2016年)

摘要

本研究將提出一套「虛擬塑形」(Virtual Sculpturing)的系統。透過影像擷取裝置偵測使用者食指尖端作為觸覺點(Haptic Interface point, HIP)並利用觸覺點與空間中物件網格之相對位置以及物件表面的深度資訊作為依據，以相似於顛簸映射(Bump-Mapping)的原理建構出觸覺點及物件網格間之虛擬接觸力(Virtual Contact Force)。
本研究將會在物件上建構一套基於力學的材料模型。當虛擬接觸力超出材料的降伏強度時，利用虛擬接觸力所造成的變形量以高斯分布改變物件表面之深度資訊作為虛擬形變。一旦物件表面之深度資訊改變時，著色器(Shader)所渲染出的模型也將隨之改變，藉此更動物件表面之視覺效果，讓使用者可以使用手部去對物件表面塑形並看到物件表面外型的改變，同時感受到塑形過程的虛擬力回饋，能使視覺及觸覺渲染達到同步交互作用之需求。
以本實驗的實驗結果，不使用法向量映射而使用位移映射中密鋪等級20的參數在視覺回饋及效能擁有最佳的結果，同時在力學渲染上也能有限度的同時滿足材料的物理特性以及虛擬接觸力回饋的體驗。

關鍵字

電腦圖學 ； 虛擬實境 ； 虛擬塑形

並列摘要

This research will propose a system called Virtual Sculpturing. By capturing user’s index fingertip as a HIP (Haptic Interaction Point) and using the spatial relations between HIP and mesh in the environment, we can construct Virtual Contact Force between HIP and the mesh as the similar concept of Bump-Mapping.
This research will construct a mechanics-based material model. When Virtual Contact Force reaches yielding strength of the material, the displacement caused by Virtual Contact Force will be applied to Gaussian Deformation to change depth information of the mesh surface. Once depth information changed, the mesh rendered by shader will update and change the visual effect. This system not only let users deformed the mesh and see the result simultaneously, but also feel the force feedback during deforming process. It shows the system can satisfied visual and force rendering interaction at the same time.
Due to the experiment result, not using Normal-mapping but Displacement-mapping with tessellation level 20 has the best result of visual effect and performance; force rendering result is also satisfied material properties and Virtual Contact Force experience.

並列關鍵字

Computer Graphic ； Virtual Reality ； Virtual Sculpturing

參考文獻

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