虛擬工程環境的碰撞偵測策略

虛擬工程利用各種計算的方法在電腦中模擬及視覺化一個工程場景，而碰撞偵測是使虛擬工程走向擬真的重要計算方法之一。對照真實的工程場景，工程過程中的所以碰撞都該盡可能地迴避，因此電腦程式在模擬一個虛擬工程場景時，也需要不停地檢查所有的物件是否發生碰撞。即使現在一般的電腦已足以應付普通程度數量的碰撞偵測計算，一旦要處理的工程環境變得複雜且巨大時，進行碰撞偵測的計算花費將會變得非常大。因此，此研究集中於找出有效率的方法來進行碰撞偵測。虛擬工程環境的規模及要求的模擬精確度與碰撞偵測的計算效率有很大的關係。有些碰撞偵測演算法可以藉由多種邏輯狀況快速的指出兩個物件是否發生碰撞，而另外有些演算法不但能指出碰撞的情況，還更能回傳兩個物件的最短距離。研究中作者利用球體及圓柱來模擬工程環境中的機具及工桯元件(樑與柱)，利用這些基本形狀的組合來進行距離計算，能有效節省計算花費的時間。研究中發展出來的演算法VC-Collide利用這些模擬方法，能讓使用者檢驗虛擬工程環境中預期外的碰撞。此演算法擁有以下的優勢：(1) 不僅指出兩物件是否碰撞且能回傳兩個物件間的距離，(2) 利用球體跟圓柱的組合來模擬工程環境中的物件，可以提供更多有效率的選擇，(3) 利用工程環境的特性，使用最佳的碰撞偵測方法組合。研究中將在三個環境中測試VC-Collide的效能，三個環境分別是小型（683個元件）、大型（2143個元件）及高樓（2612個元件）。此外，知名泛用的物理引擎ODE (Open Dynamic Engine)也會跟VC-Collide一起進行測試。試驗結果指出VC-Collide能在即時處理的限制(二十分之一秒)之內完全三個環境中所有的碰撞測試，同時也能表現出比ODE更高的效能。 VC-Collide在未來能成為即時虛擬工程環境的基礎計算核心。工程吊裝模擬、機器人的路徑規劃與空間利用分析等需要虛擬工程碰撞偵測的研究，都能利用此研究的結果。

關鍵字

工程吊車；碰撞偵測；虛擬實境；工程模擬；邊界盒

並列摘要

Collision detection is one of the most important computational methods required to simulate virtual construction on computers. Similarly to an actual construction site, all collisions need to be avoided in the virtual world during the construction process. This means that the computer program which generates the virtual construction scenarios needs to continuously check the collision status of all objects. Although computing the collision status of an object may not consume much time using modern computer equipment, when the construction site is complex or the number of objects on the construction site is large, the computational cost for checking the collisions can be very high. Therefore, this research aims to find efficient methods for performing the collision detection. The computational efficiency of a collision detection method depends highly on the application scenario and precision requirements. Some collision detection algorithms can determine the collision status (i.e. whether or not a collision has occurred) quickly with multiple logic statements while other algorithms can return both the collision status and the shortest distance to the next collision in the case of a collision free event. In this research, we approximate construction machineries and structural elements on a construction site by using spheres and cylinders. By properly modeling the object using primitive shapes, the computational cost for collision detection can be significantly reduced. The VC-COLLIDE algorithm has been developed in this research. It has the following major advantages: (1) it returns not only the collision status but also the distance to a collision; (2) spherical and cylindrical box combinations provides more efficient choices; and (3) it takes note of the construction scenario, and chooses the best collision detection solution for the specific virtual construction scenario. VC-COLLIDE has been implemented and tested by using three construction scenarios: small building scenarios (683 objects), large building scenarios (2143 objects) and tall building scenarios (2612 objects). Open Dynamic Engine (ODE), a widely used physics engine, is also involved in the tests. The test results indicate that VC-COLLIDE can complete all the collision checks within 1/20th of a second, the upper bound of real-time refresh time in the three testing environments. The results also indicate that the performance of VC-COLLIDE is significantly better than the performance using ODE. In the future, VC-COLLIDE can be used as a basic computation kernel to render a virtual construction site in real time. It can also support studies on erection simulations, motion planning of construction machines and site layout planning, all of which require efficient collision detection methods to visualize dynamic construction scenarios.

並列關鍵字

construction crane ； collision detection ； virtual reality ； construction simulation ； bounding volume box

參考文獻

Bergen, G. van den. (1997) “Efficient collision detection of complex deformable models using AABB Trees,” Journal of Graphics Tools, 2(4): 1-13.

Clayton, M. J., Warden, R. B. and Parker, T. W. (2002) “Virtual construction of architecture using 3D CAD and simulation,” Automation in Construction, 11(2): 227-235.

Kang, S. C. and Miranda, E. (2006) “Planning and visualization for automated robotic crane erection processes in construction,” Automation in Construction, 15(4): 398-414.

Koo, B. and Fischer, M. (2000) “Feasibility study of 4D CAD in commercial construction,” Journal of Construction Engineering and Management, 126(4): 251-260.

Lin, M. C. (1993) “Efficient collision detection for animation and robotics,” PhD thesis, Department of Electrical Engineering and Computer Science, University of California, Berkeley

國際替代計量

虛擬工程環境的碰撞偵測策略

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