三維動態網格漸進式播放與串流化傳輸之應用

Applications of Dynamic 3D Meshes with Progressive Rendering and Stream Transmitting

高啟綱(Chi-Kang Kao)

指導教授 ： 鍾斌賢

中原大學/工學院/電子工程研究所/博士(2013年)

https://doi.org/10.6840/cycu201301100

摘要

雖然近年來二維影像與動畫技術蓬勃發展，已有許多成熟的壓縮方法，然而三維動態網格，又稱為三維動畫的領域當中，尚沒有一個令人熟知且優異的壓縮方法。三維動畫必須記錄模型各個點在不同影格的座標位置，所以需要大量的記憶體空間與計算量來處理，使得三維動畫的相關應用發展不容易。雖然許多學者陸續提出三維動畫壓縮法，卻都還有一些缺點尚待改進，使得尋找一個壓縮法能夠適用於各種三維動畫，還能夠具有高壓縮率、低執行時間成為熱門且值得研究的主題。

在現今科技發達的時代，一個使用者可能擁有多套瀏覽多媒體的設備，現有的影音平台對同一部影片只提供一種品質(解析度)的動畫，並不會因為使用者的電腦環境不同而做改變。使得使用低效能的配備瀏覽將發生頻寬不足導致過長的等待，無法即時的看到所想要觀看的影片。

本論文提出了一個新的三維動畫表示法，稱為漸進式動畫。漸進式動畫隨著資料讀取或傳送的過程將使得正在播放的模型由模糊而漸漸變的清晰。而漸進式動畫最重要的技術就是為了減少點座標所占有的龐大資料量。除此之外，為了能夠達到漸進式播放，所使用的壓縮法也要能夠支援逐步還原的效果。

在本論文中，我們提出的第一個方法是以分群式主成份分析為基礎的壓縮法。我們改良解壓縮的公式，使得三維動畫在重建的過程能夠隨著增加一個主成份就更新一次解析度，進而實現漸進式播放。這個方法也提出了兩種策略來決定主成分傳輸的順序，而實驗結果顯示如果依照計算好的傳輸順序作更新，可以有效降低重建的誤差。除此之外，額外所增加的負擔(記錄傳輸順序所需要的資料量)也是微乎其微。

第二個方法我們融合了簡化的方法與第一個方法，改進了第一個方法不能改變動畫點數與三角面數的缺點。我們發現主成份彼此獨立的特性，發明出將點分裂運算子與主成份結合在一起的技術。使得漸進式動畫不僅能夠改變點座標的精確度，也能夠改變動畫其外型特徵的精確度。我們實作了一套模擬系統，證明使用我們的方法能夠即時且自動地提升三維動畫的解析度，或是完全交由使用者自行控制解析度的變動。最後，本論文所提出的漸進式動畫也使得三維動畫更適應於網路上的播放與傳輸。

關鍵字

三維動態網格壓縮 ； 三維動畫簡化 ； 串流化傳輸 ； 漸進式播放三維動畫

並列摘要

Although 2D image and animation compression techniques have become more popular and sophisticated, there are very few popular and better compression methods for 3D animation. Since saving all the vertex displacements at each frame would require a large amount of memory space and calculation, it is difficult to develop the applications for 3D animation. There are a few of 3D animation compression methods were proposed. However, the previous methods have some disadvantages that need to be improved. Thus, developing a compression method that is suitable for 3D animation with higher compression ratio and less computation time has become one of the important topics to be studied.

As the mobile phone become popular, a user may have multiple devices for viewing the media content through the network. However, the media provider usually provides only one resolution content for each animation, which the media provider should provide different resolution according to performance of each device. Otherwise, the long latency of downloading happens on browsing by lower performance device.

This study aimed to propose a new representation for 3D animation, where the new representation is called progressive animation. The progressive animation renders the 3D animation model from blur to clear as the data keep transmitting and loading. The first important technique of progressive animation in this study is to compress the huge amount of vertex displacements through all the frames. Moreover, to achieve the progressive rendering, the compression and simplification methods should support reconstructing the animation step by step.

In this study, we first propose a compression method based on clustered principal component analysis (PCA). We rewrite the formula of PCA decompression, reconstructing the 3D animation by applying a principle component (PC) once an update. The progressive rendering from coarse to detail is realized by applying PCs incrementally. This method also provides two strategies for deciding the transmitting sequence of the PCs. The result shows that the ordered transmitting sequences is effective for reducing the distortion, and the extra overhead is extremely low.

The second method applies the simplification into the first method, which improves the disadvantages of the first method that always presents all the vertices for any resolutions. We control the independent properties of PCs and successfully combine the vertex split operator with PC. Therefore, the progressive animation is able to update connectivity or vertex displacements according to user’s environment. As the results, the resolution of animation can be free to change at real-time, where the resolution can be increased automatically or even controlled by user. Moreover, the progressive animation is more suitable for transmitting and rendering through the network.

並列關鍵字

3D Animation Simplification ； Dynamic 3D Meshes Compression ； Stream Transmitting ； Progressive Rendering of Dynamic 3D Meshes

參考文獻

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