隨著地形模擬視覺的發展，地形廣泛地應用於各種遊戲及模擬環境上，為了符合物理定律下所模擬的效果，一成不變的地形已逐漸被能隨著事件而改變的地形所取代，然而在現今風靡全球的戰爭遊戲中依然無法做到此要求。為了能在戰爭模擬環境中以更擬真的方式來顯示整個戰局，我們根據物理定律，進行砲彈擊中地形之即時動態模擬。但因建構三維場景模擬，通常整個場景計算量非常大，因此常無法有效的應用於各種效能的系統上，有鑑於此，及為了地形需即時反應砲彈所造成的變化，我們提出了一個利用細節層次的概念呈現地形，並結合快速改變地形資料的方式來呈現地形與砲彈之即時互動模擬。首先，由於地形在整個場景中的資料量非常的大，為了更有效率的繪製地形，因此以細節層次方法來建置地形，以提供使用者在觀看場景間不同距離時，得以看到最佳的結果。在模擬中我們利用碰撞偵測，使得砲彈擊中地形後以物理模型得到所產生的彈坑，透過階層式的樹狀結構快速且有效率的改變受影響的區域，並產生彈坑貼圖材質與利用對彈坑區域的細分，以求更佳的視覺效果。利用這樣的方式，使得當有多層細節層次時，可以快速的得知受影響的範圍並做出改變，也因為細節層次的關係，彈坑的表現上能以更加精細。由於細節層次與動態地形的配合大幅降低了運算量，因此能應用在各種需要即時互動之遊戲及模擬等。

Terrain is used in various computer games and simulations along with the development of computer visualization. However, most terrain environment cannot be deformed by the effect of external forces in real-time nowadays. Real-time deformation in most game engines use texturing to create the illusion of deformation because it may be expensive. In order to simulate terrain realistically, terrain needs to be modified by the external forces in real-time and the deformed area should be changed not only illusion but also position; therefore, an object will change position when an object moves through the deformed area.
In this thesis we proposed an algorithm for battlefields to generate shell craters randomly. We presented a new terrain deformation approach that is able to generate shell craters in real-time. Tanks will low it position when they move to shell craters. Because the terrain data are too massive to render efficiently, we constructed our terrain mesh by view-dependent level of detail approach basically. Then, we used collision detection to detect when and where the shells reach the ground. After the shells exploded, terrain was modified by half-ellipsoid model in the explosion theory as the physical based model of crater. Terrain deforms rapidly through a hierarchical structure based on the proposed algorithm. After the deformation, we synthesize a new texture of shell craters for greater visualization.
In this approach, we could deform the exploded area efficiently even if the level of detail is fine. Shell craters present finer result when the level of detail is finer. The combination of view-dependent level of details and hierarchical search tree reduces the computation observably. Thus, this approach can be used in various computer games and simulations real-time in battlefields.

Chapter 1 導論 1
Chapter 2 文獻探討 4
2.1. 細節層次 4
2.2. 地形資料結構 6
2.2.1. 三角不規則型格網 6
2.2.2. 直角不規則型格網 7
2.2.3. 混合型格網 9
2.3. 地形動態改變 9
Chapter 3 研究方法 12
3.1. 階層搜尋樹 12
3.1.1. 網格結構 13
3.1.2. 網格鄰邊關係 14
3.1.3. 網格搜尋 15
3.2. 碰撞偵測 15
3.3. 彈坑產生 17
3.3.1. 地形動態改變 18
3.3.2. 網格動態分割 19
3.3.3. 貼圖變化 20
Chapter 4 實驗與結果 23
4.1. 使用者介面 23
4.2. 場景建構 24
4.3. 陰影產生 24
4.4. 爆炸模擬 25
4.5. 實驗結果 27
Chapter 5 結論 30
參考文獻 31

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