【摘要】：大自然中的諸多景象如云、雪、煙等不是簡單的可以用數(shù)字化表示的,這些自然景物運(yùn)動規(guī)律時(shí)刻都在變化,形狀、顏色等屬性也會隨著運(yùn)動規(guī)律的變化而變化。隨著圖形學(xué)的發(fā)展和游戲產(chǎn)業(yè)的需求日益提高,不僅對模擬顯示畫面的真實(shí)感有了更高的要求,作為虛擬現(xiàn)實(shí)的一部分,景物與環(huán)境間交互作用的研究也是很重要的,如何有效、實(shí)時(shí)地模擬自然景物是圖形學(xué)研究的關(guān)鍵。雪景是人們廣為熟知的一種自然景象,在影視特效、電視廣告、電子游戲中有著不可或缺的地位,尤其是在雪災(zāi)的預(yù)防中,雪景的模擬有著積極的意義。雪景作為自然場景的一部分,得到了越來越多的學(xué)者的青睞和研究。 現(xiàn)有模擬雪景的方法不是以犧牲實(shí)時(shí)性為代價(jià)就是以犧牲逼真性為代價(jià),為了實(shí)現(xiàn)雪景模擬真實(shí)性與實(shí)時(shí)性的統(tǒng)一取得較為理想的結(jié)果,本文提出了基于粒子系統(tǒng)和物理模型的動態(tài)雪景模擬算法,在保證系統(tǒng)實(shí)時(shí)性的情況下實(shí)現(xiàn)更為逼真的雪景模擬。 (1)建立雪粒子系統(tǒng)模型。在粒子系統(tǒng)運(yùn)行原理基礎(chǔ)上,結(jié)合雪花本身特點(diǎn)完成雪粒子系統(tǒng)的分析和實(shí)現(xiàn)過程,包括雪粒子各屬性的研究和相關(guān)屬性更新方法等。采用紋理映射技術(shù)和公告板技術(shù)優(yōu)化、完善雪粒子的繪制工作,實(shí)現(xiàn)了基于公告板的雪花繪制,并提出了重置死亡粒子的方法。 (2)設(shè)計(jì)了靈活的雪花物理運(yùn)動模型。本文考慮了重力、浮力、向心力等對降雪的影響,在分析了外力影響下雪花飄落的運(yùn)動規(guī)律后構(gòu)造出其運(yùn)動方程,并把向心力作為可供選項(xiàng)隨機(jī)賦予粒子,隨力場的改變實(shí)時(shí)地更新雪花的速度、位置數(shù)據(jù),解決了粒子下落過程中運(yùn)動軌跡單一的問題,體現(xiàn)出自然界中雪花降落來回?fù)u曳、飄忽不定的運(yùn)動特性。 (3)設(shè)計(jì)了雪花的碰撞檢測模塊。分析了雪花碰撞的兩種情況并提出了每種情況下雪花碰撞后的速度和位置更新方法,通過位置和速度的改變表現(xiàn)出雪花與其他虛擬物體之間發(fā)生的碰撞關(guān)系。 (4)提出了將高度作為雪堆積的依據(jù),通過場景中物體高度的變化量繪制雪的堆積,并用概率的方法衡量某處的堆積是否穩(wěn)定。 最后,對模擬系統(tǒng)的實(shí)時(shí)性優(yōu)化方法做了討論,并利用OpenGL提供的渲染功能完成了實(shí)時(shí)性保證下的真實(shí)感雪景的模擬。
[Abstract]:Many scenes in nature, such as clouds, snow, smoke and so on, can not be simply represented by digitization. These natural scenery moving laws are changing at all times, shape, color and other attributes will also change with the change of motion law. With the development of graphics and the increasing demand of the game industry, there is not only a higher demand for the realistic sense of the simulated display screen, but also an important research on the interaction between scene and environment as a part of virtual reality. How to simulate natural scene effectively and in real time is the key of graphic research. Snow scene is a kind of natural scene widely known to people. It plays an indispensable role in film and television special effects, TV advertisements and video games, especially in the prevention of snow disaster, the simulation of snow scene has a positive significance. As a part of natural scene, snowscape has been favored and studied by more and more scholars. The present methods of snow scene simulation are either at the expense of real time or at the expense of realism. In order to achieve the unity of simulation authenticity and real time of snow scene, the ideal results are obtained. A dynamic snow scene simulation algorithm based on particle system and physical model is proposed in this paper. (1) the model of snow particle system is established. On the basis of the operation principle of particle system, the analysis and implementation process of snow particle system is completed according to the characteristics of snowflake, including the research of snow particle properties and the updating methods of related attributes. The texture mapping technique and bulletin board technology are used to optimize the snow particle rendering. The snowflake rendering based on the bulletin board is realized and the method to reset the dead particle is proposed. (2) A flexible physical model of snowflake motion is designed. In this paper, the effects of gravity, buoyancy and centripetal force on snowfall are considered. After analyzing the motion law of snowflake falling under the influence of external force, the motion equation of snowflake falling is constructed, and the centripetal force is randomly assigned to the particle as the available option. With the change of force field, the velocity and position data of snowflakes are updated in real time, which solves the problem of single track in the falling process of particles, and reflects the moving characteristics of snowflakes falling back and forth in nature. (3) the collision detection module of snowflake is designed. Two cases of snowflake collision are analyzed and the updating method of velocity and position after snowflake collision in each case is proposed. The collision relationship between snowflake and other virtual objects is shown by changing the position and velocity. (4) the height is taken as the basis of snow accumulation, and the snow accumulation is plotted by the change of object height in scene, and the stability of snow accumulation is measured by the method of probability. Finally, the real-time optimization method of the simulation system is discussed, and the simulation of the realistic snow scene under the real-time guarantee is completed by using the rendering function provided by OpenGL.
【學(xué)位授予單位】：河南師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2011
【分類號】：TP391.9

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