風格轉換在電腦圖學領域中一直是許多人研究的主題，由於藝術創作通常較為費時，尤其對於藝術造詣不高的人更是如此。本篇著眼於將一段影像動畫轉換為具有加拿大數位藝術家Patrick Seymour作品的風格樣式，其作品多由線條所構成。利用線條的不同形式，如線條流向、粗細變化、線條寬度以及線條的間隔距離，為作品創造出亮暗對比。使作品不僅不會因為只由線條建構而成感到單調，甚至能透過亮部與暗部產生立體錯覺，進而有躍然紙上的效果。

本篇利用 Vector Graphics Animation with Time-Varying Topology~cite{Dalstein:2015} 產生動畫每個幀的輪廓，接著針對關鍵幀進行張量場的設計。擁有關鍵幀中各區塊的張量場後，對所有幀的各區塊進行計算產生相應的張量場，並將張量場以流線的形式呈現，產生出最終具有線條藝術風格的動畫成果。過去關於動態張量場設計的圖學研究，多利用一般的線性內插產生關鍵幀之間的張量場。由於本篇的應用並非單純將張量場視覺化，而是希望與圖形輪廓具有一定的連結性，若使用線性內插產生出的結果可能會與動畫本身不相符。如何僅依靠每個幀各區域的輪廓以及關鍵幀的張量場，生成平順流暢的動畫便是本篇研究主題。利用本篇提出之方法，可以適用於大部分的動畫產生，並得到平滑好看的結果。

There are many pieces of research about style transfer in computer graphics. From the early use of traditional graphics to simulate sketch strokes, to the recent application of deep learning to style transfer, people try to generate digital images with different styles. It’s because the creation of artworks is quite difficult and time-consuming. Thus, there are many kinds of researches for different kinds of styles transfer.

The purpose of our research is transferring the style of animation to hypnotic line art which is made by the Canada digital artist – Patrick Seymour. He uses a set of lines to fill a patch and presents the texture of the patch through the direction, the width, the sharpness of the lines. The different type of lines makes the image appear to be 3D.

Our system uses Vector Graphics Animation with Time-Varying Topology~cite{Dalstein:2015} to generate a contour animation and a segmentation animation. Then uses WYSIWYG Hypnotic Line Art Design to design the tensor fields of all keyframes. After having the tensor fields, we create the time-varying tensor fields for the whole animation. We generate the streamlines for every patch of every frame based on the time-varying tensor fields. Combine the streamlines and the contour animation to output the final hypnotic line art style animation.

How to generate a time-varying field is the main issue in our work. The method that we use will be detailed described in the following chapter. With our work, user can easily create a smooth and visually satisfying hypnotic line art animation.

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