一般來說，把一大塊地形模型載入到記憶體做展示是不切實際的。在此，我們將大區域地形模型切割成許多矩形小地塊，並且動態地載入所需的小地塊到記憶體中展示。在增進視覺效能而不減少視覺品質的要求下，每個地形區塊各自擁有變動的解析度，解析度會自動根據螢幕空間誤差 (screen-space error) 作調整；也就是每個地形區塊都有視點相關多重解析度模塑 (view-dependent multiresolution modeling) 的功能。在這種情形下，當相鄰地塊有不同解析度時，在邊界就可能產生破裂。在此我們提出重新三角化邊界 (re-triangulated boundary method) 的方法來克服這個問題。 在3D虛擬環境瀏覽的應用中，視點可能會靠近或遠離地形模型，而視野範圍也就跟著改變。為了進一步增進視覺效能及品質，我們讓地形區塊數量可以隨著視點高度自動改變。 在只有一個處理器的電腦上執行3D飛行模擬，當載入地形區塊時，虛擬環境的飛行瀏覽經常會被暫停。為了消除這個現象，我們依據最近的飛行方向來預測飛行路徑，然後利用處理器執行的空檔預先載入可能需要的地形區塊。 For a large terrain model, it is generally impractical to load the whole terrain model into the main memory. We here partition a large terrain model into blocks and then dynamically load the necessary terrain blocks into the memory for rendering. To improve the visualization performance without reducing the visual quality, every terrain block has its own variant resolution and the variable resolution is automatically adapted based on the screen-space error. That is, every terrain block possesses the view-dependent multiresolution modeling function. In such a case, cracks between two adjacent blocks with different resolutions are always generated. We here propose a re-triangulated boundary method to overcome the problem. During fly-through applications, the viewpoint may move toward or away from the terrain model, then the view-scope is changed. To further improve the visualization performance, the active block number is automatically adapted according to the height of the viewpoint. In a one-processor computer, the fly through always suspends during loading necessary terrain blocks. To reduce the phenomenon, we predict the flight path to pre-load the necessary blocks in advance based on the last flying directions.
