應用元球和三□表面重構的冰融化模擬以及在圖形處理器上之加速

Abstract

在本篇論文中，我們提出了一個新的冰融化模擬方法。這個方法是以粒子為基礎的模型進行融化模擬。我們將場景中的粒子分為兩種：冰粒子與水粒子。冰粒子用來表示場景中的冰，而水粒子用來表示水。

在我們的方法中，冰粒子含有一特別屬性，用來存取冰粒子附近水的體積，我們稱之為虛擬水體積。冰粒子在吸收熱能後會將融化的部分轉化為虛擬水體積，我們運用在冰模型表面傳遞虛擬水體積的方式模擬融化產生的水以及其在冰表面的流動。當冰粒子中的虛擬水體積超過預設體積時，則會產生水粒子。

針對冰模型的融化內縮，我們使用新的方法計算標量場中各頂點的標量值，這個方法將冰粒子的潛熱及虛擬水體積作為標量值計算的參數。接著我們應用三維表面重構的方法建立冰模型的多邊形網格。

在渲染場景的部分，我們在場景中同時對冰粒子所生成的多邊形網格及水粒子所代表的元球進行光線追蹤。我們將網格及元球分別使用階層包圍盒建構出階層式架構，以利於射線的碰撞測試。我們的方法實作於圖形處理器上，在效能上有不錯的表現。

In this thesis, we propose a novel ice melting simulation method based on a particle-based model. We have two types of particles: ice particles and water particles. The ice particles represent the ice model and the water particles represent water.

In our method, ice particles have an attribute named virtual water volume, which is used to represent the fluid volume around this ice particle. An ice particle may increase its amount of virtual water volume when the latent heat of the ice particle increases. We simulate fluid flowing on the surface of the ice model by transferring the virtual water volume between ice particles. A water particle is produced if the virtual water volume in an ice particle is larger than default volume of the water particle.

For smoothly shrinking ice model, we propose a new method to calculate the potential field. The latent heat of ice particles and virtual water volume are taken into account for computing the potential field. We use marching cubes to construct the polygonal mesh for the ice model.

To render the ice model and water particles, we propose a ray tracing method to render them. The ice model is represented by the polygonal mesh, and water particles are constructed into metaballs. We use the bounding volume hierarchy (BVH) to create hierarchy constructions to accelerate the process of ray tracing. Our method has been implemented on GPUs. Experiment results show that our method is efficient and compute realistic ice melting simulation.