【摘要】：虛擬現(xiàn)實(shí)場(chǎng)景的仿真是虛擬現(xiàn)實(shí)領(lǐng)域的基礎(chǔ)工作。海浪場(chǎng)景是虛擬現(xiàn)實(shí)場(chǎng)景中較為復(fù)雜的場(chǎng)景之一。首先,海浪的形狀復(fù)雜,不能由簡(jiǎn)單幾何體構(gòu)造,在使用基本幾何圖元構(gòu)造時(shí)需要大量的數(shù)據(jù)。其次,海浪是動(dòng)態(tài)變化的,每一次變化都要求計(jì)算機(jī)重新進(jìn)行一次繪制。再次,海浪的形成受多種因素的影響,波形的變化規(guī)律多種多樣,海浪的形態(tài)在不同的時(shí)刻具有隨機(jī)性。最后,海洋環(huán)境多樣,天氣多變,環(huán)境光源需要考慮各種法線的反射與折射。海浪最終顏色不宜確定。如果光照不能處理好,將極大影響海浪模擬的真實(shí)性。正是由于海浪場(chǎng)景的復(fù)雜,海浪的建模與繪制存在許多難點(diǎn)。本文分別對(duì)海浪場(chǎng)景的建模與繪制技術(shù)進(jìn)行分析與研究。首先,針對(duì)海浪譜方法在建模時(shí)存在的周期性重復(fù)現(xiàn)象及真實(shí)感不強(qiáng)的問(wèn)題,本文提出基于擾動(dòng)的海浪譜建模方法。為了在海浪譜上疊加柏林噪音擾動(dòng),給出依據(jù)視點(diǎn)位置的疊加策略。當(dāng)視景體中出現(xiàn)較大面積海面時(shí),依據(jù)本文給出的疊加公式,將柏林噪音與海浪譜生成的高度圖進(jìn)行疊加,使得相應(yīng)海面的高度圖發(fā)生變化,進(jìn)而減弱周期性重復(fù)現(xiàn)象并提高海面真實(shí)感。其次,針對(duì)光線跟蹤算法在動(dòng)態(tài)海浪繪制時(shí)幀率較低的問(wèn)題,本文從海浪場(chǎng)景三角形分布不均勻的特點(diǎn)出發(fā),提出適宜于海浪場(chǎng)景的基于簡(jiǎn)單光照的光線跟蹤算法及其加速結(jié)構(gòu)。光線跟蹤算法的光線跟蹤策略要依據(jù)光照模型,海浪場(chǎng)景中全局光照模型的光線跟蹤策略有許多的跟蹤是不必要的,因此,提出簡(jiǎn)化折射與限制反射光線條數(shù)的簡(jiǎn)單光照模型。海浪場(chǎng)景中對(duì)象大多分布在海面高度一定正負(fù)范圍內(nèi),在加速結(jié)構(gòu)建立時(shí),相當(dāng)多的時(shí)間消耗在了海面上部與天空盒之間的空白區(qū)域,因此提出多層次的加速結(jié)構(gòu)及選擇性更新的策略。最后,分析海面漂浮物漂移過(guò)程的風(fēng)流條件對(duì)運(yùn)動(dòng)的影響,研究蒙特卡洛方法在漂移模型計(jì)算中的應(yīng)用,基于本文提出的海浪建模與繪制技術(shù),建立一個(gè)用于飄移模型的海面三維可視化系統(tǒng)。
[Abstract]:Virtual reality scene simulation is the basic work in the field of virtual reality. Wave scene is one of the more complex scenes in virtual reality. First of all, the shape of waves is complex and can not be constructed by simple geometry, and a lot of data are needed when constructing with basic geometric graph elements. Secondly, the waves are dynamic, each change requires a computer to redraw. Thirdly, the formation of waves is influenced by many factors, the variation of wave waves is varied, and the shape of waves is random at different times. Finally, the marine environment is diverse and the weather is changeable, so the reflection and refraction of various normal lines should be considered. The final color of the waves is not certain. If the illumination can not be handled well, it will greatly affect the authenticity of wave simulation. Because of the complexity of wave scene, there are many difficulties in ocean wave modeling and rendering. In this paper, the modeling and rendering techniques of ocean wave scene are analyzed and studied. Firstly, in order to solve the problem of periodic repetition and lack of reality in wave spectrum modeling, a wave spectrum modeling method based on disturbance is proposed in this paper. In order to superimpose Berlin noise disturbance on wave spectrum, a superposition strategy based on viewpoint position is proposed. When a large area of sea surface appears in the visual object, according to the superposition formula given in this paper, the height map generated by the Berlin noise and the wave spectrum is superimposed to make the corresponding sea surface height map change. Then the periodic repetition phenomenon is weakened and the sea surface reality is improved. Secondly, aiming at the problem of low frame rate of ray-tracing algorithm in dynamic ocean wave rendering, this paper starts from the characteristics of uneven triangular distribution of ocean wave scene. A ray-tracking algorithm based on simple illumination and its acceleration structure are proposed for ocean wave scene. The ray-tracking strategy of the ray-tracking algorithm is based on the illumination model, and many of the ray-tracking strategies of the global illumination model in the wave scene are unnecessary. Therefore, a simple illumination model which simplifies refraction and limits the number of reflected light lines is proposed. Most of the objects in the ocean wave scene are distributed in the positive and negative range of sea surface height. When the acceleration structure is set up, a considerable amount of time is spent in the blank area between the upper sea surface and the sky box. Therefore, a multi-level accelerating structure and selective updating strategy are proposed. Finally, the effect of wind flow conditions on the motion of floating objects is analyzed, and the application of Monte Carlo method to the calculation of drift model is studied, based on the wave modeling and drawing technology proposed in this paper. A three-dimensional sea surface visualization system for transport model is established.
【學(xué)位授予單位】：哈爾濱工程大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TP391.9

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