- 學位論文
以Lattice Boltzmann Method為基礎的NPR水彩繪畫模擬
Simulating NPR Watercolor Painting based on the Lattice Boltzmann Method
摘要
Non-Photorealistic Rendering(NPR)在圖學的領域中是一個重要的課題，此一特殊的成像方式不以物品的擬真度為優先考量，而是著重筆觸、繪畫風格等的呈現。對於NPR水彩研究而言，模擬水在畫紙上的流動與擴散現象，是一個重要的研究項目。 在本篇論文中，我們實做了一個NPR水彩系統。首先，以3D model來建構出場景，並藉由探討水彩濃度與不同顏色顏料的互相混色來產生出具有水彩繪畫風格的視覺效果 爲了達到以上目的與模擬渲染的效果，我們利用流體力學中的Lattice Boltzmann Method(LBM)物理模型，來模擬水在2D畫布上的流動，然後藉由抽取三維模型自身的特性如輪廓以及骨架結構等，來模擬出多種水彩筆觸。 我們的筆觸由多個pixel組成，並利用Phong’s reflection model來計算出每一個pixel的顏色。因此，沿著pixel的移動，筆觸上的顏色會漸漸的轉變。利用這個方法我們可以得到自然而生動的筆觸。換言之，我們提出的方法是根據場景資訊自動產生出具有明暗效果的筆觸。 由實驗結果，我們可以得到具有自然又有趣的色彩、明暗與筆觸的NPR水彩動畫影片。
並列摘要
Non-Photorealistic Rendering (NPR) has been an important research topic in the field of Computer Graphics. Instead of highlighting the realism of CG synthesized images, NPR focus on the representation of the stroke and painter’s style. For the research of NPR watercolor, simulating water diffusion and flow in paper is an important task. In this paper, we implement a NPR watercolor system. Our scene is composed with 3D models. The special visual effects of watercolor paintings are created by simulating the color mixing and the different concentration of watercolor. To achieve the above goal and the “Brush-Washing” effect, the water flow on 2D paper is simulated based on the Lattice Boltzmann Method (LBM). Moreover, the strokes of watercolor are simulated by utilizing the auxiliary bone structures and the shapes of three-dimensional models. A stroke consists of multiple pixels. The color on each pixel is calculated by Phong’s reflection model. Therefore, the color on a stroke gradually transits from pixel to pixel. This approach creates nature and vivid appearances of strokes. In another word, our proposed method creates the tone of strokes automatically based on the 3D information of scene. As shown in the experiment results, our system synthesizes watercolor NPR animation with interesting and nature color, tone and strokes.