本文選題：雪模擬 + 粒子系統(tǒng)��； 參考：《電子科技大學(xué)》2012年碩士論文

【摘要】：利用計(jì)算機(jī)圖形學(xué)原理來(lái)真實(shí)的模擬各種自然現(xiàn)象已經(jīng)是當(dāng)今從事于虛擬現(xiàn)實(shí)仿真的研究者們的一大愿望。隨著圖形硬件的快速發(fā)展，越來(lái)越多的仿真系統(tǒng)應(yīng)用于計(jì)算機(jī)游戲、電視廣告和電影拍攝之中。雪景作為北國(guó)冬天必不可少的一種自然景觀，沒有雪景的實(shí)時(shí)模擬是無(wú)法反映出“千里冰封，萬(wàn)里雪飄”的磅礴氣勢(shì)的。目前，，在降雪場(chǎng)景模擬方面，更多的研究側(cè)重于反映其真實(shí)感，而很少考慮實(shí)時(shí)性的要求；在積雪場(chǎng)景模擬方面，大多數(shù)的研究都傾向于渲染雪花沉積的過程，即從沒有積雪到覆蓋積雪這個(gè)過程，而在大多數(shù)實(shí)現(xiàn)中也往往很少考慮實(shí)時(shí)性的要求。 本文將通過介紹并分析雪模擬的一些相關(guān)方法，對(duì)其原理作進(jìn)一步探究，主要包括：粒子系統(tǒng)，雪花物理運(yùn)動(dòng)規(guī)律，降雪的紋理繪制以及基于深度圖的靜態(tài)積雪模型。通過研究并融合這些系統(tǒng)理論，使我們的雪場(chǎng)景模擬系統(tǒng)能夠滿足實(shí)時(shí)性的要求。本文的主要工作如下： 1）分析并討論了降雪粒子在空中運(yùn)動(dòng)時(shí)的物理運(yùn)動(dòng)模型，并利用GPU相關(guān)技術(shù)，使得在每一次渲染更新前，能通過前一次降雪粒子的位置、速度等屬性，根據(jù)雪花的物理運(yùn)動(dòng)規(guī)律實(shí)時(shí)計(jì)算降雪粒子的當(dāng)前幀的相關(guān)屬性，從而實(shí)現(xiàn)了在視點(diǎn)近景范圍內(nèi)的降雪模擬。 2）將動(dòng)態(tài)紋理的相關(guān)理論應(yīng)用于遠(yuǎn)景處降雪場(chǎng)景的實(shí)時(shí)繪制，提出了基于視點(diǎn)的雙半椎體的繪制方法，并討論了視差效果的實(shí)現(xiàn)手段。 3）提出了快速真實(shí)的靜態(tài)積雪渲染方法。基于切比雪夫不等式的概率學(xué)理論，將不等式的概率上限近似作是對(duì)應(yīng)點(diǎn)的積雪厚度比率，通過硬件濾波，模擬出比較具有真實(shí)感的“淺雪區(qū)”效果。 4）結(jié)合可編程流水線、LOD、點(diǎn)精靈、RTT等相關(guān)技術(shù)，詳細(xì)地闡述了上述提出的相關(guān)算法的設(shè)計(jì)方案和實(shí)現(xiàn)方法，最后進(jìn)行實(shí)踐驗(yàn)證，實(shí)現(xiàn)了基于GPU加速的實(shí)時(shí)雪景模擬系統(tǒng)，實(shí)驗(yàn)結(jié)果表明，所實(shí)現(xiàn)的算法能夠滿足一定的實(shí)時(shí)效率的要求。
[Abstract]:Using the principle of computer graphics to simulate all kinds of natural phenomena is now a great desire of researchers engaged in virtual reality simulation. With the rapid development of graphics hardware, more and more simulation systems are used in computer games, TV advertising and film shooting. Snowscape is an indispensable natural landscape in North China in winter. Without the real-time simulation of snowscape, it is impossible to reflect the momentum of "thousands of miles of ice, thousands of miles of snow floating". At present, in the snow scene simulation, more researches focus on reflecting its reality, but few consider the requirement of real-time. In snow scene simulation, most of the research tend to render the snowflake deposition process. That is, from no snow cover to snow cover, but in most implementations, the requirement of real time is seldom considered. This paper will introduce and analyze some related methods of snow simulation, and further explore its principle, including particle system, snowflake physical motion law, snow texture rendering and static snow cover model based on depth map. By studying and merging these system theories, our snow scene simulation system can meet the requirement of real-time. The main work of this paper is as follows: 1) the physical motion model of snowfall particles in the air is analyzed and discussed. By using the GPU correlation technology, the position, velocity and other attributes of the previous snowfall particle can be passed before each render update. According to the physical motion law of snowflakes, the related properties of the current frame of snowfall particles are calculated in real time, and the snowfall simulation in the close-range of view is realized. 2) the theory of dynamic texture is applied to the real-time rendering of snowfall scene in the foreground, and a method of rendering double hemispheric body based on viewpoint is proposed, and the method to realize the parallax effect is discussed. 3) A fast and real static snow rendering method is proposed. Based on the probabilistic theory of Chebyshev's inequality, the probability upper limit of the inequality is approximated as the ratio of snow thickness at the corresponding point. Through hardware filtering, the effect of "shallow snow zone" with realistic sense is simulated. 4) combined with the relevant technologies such as programmable pipeline and point wizard, the design scheme and implementation method of the above algorithms are described in detail. Finally, the practical verification is carried out, and the real-time snow scene simulation system based on GPU acceleration is realized. Experimental results show that the proposed algorithm can meet the requirements of real-time efficiency.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類號(hào)】：TP391.41

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