Sketch and animation assistants for novices

Abstract

Sketch and animation are two frequently adopted art forms for expressing ideas and conceptions. However, even for professional artists, producing visually pleasing results requires substantial expertise and effort. Since sketch and animation are difficult to master, drawing assistant tools are necessary for novices. However, existing commercially available software packages for sketch and animation, such as Adobe Photoshop, Toon Boom, demand a steep learning curve and are rather difficult to master for novices, further hampering users’ creation process. In this thesis, we present two user-friendly assistant tools, EZ-Sketching and Live Sketch, to ease the creation process of sketch and animation respectively for novice users. We also propose an error-tolerant target acquisition technique, 2D-Dragger, to solve the common accessibility problems in existing tools on touch devices. EZ-Sketching, a novel image-guided drawing interface, uses a tracing paradigm and automatically corrects sketch lines roughly traced over an image by analyzing and utilizing the image features being traced. While previous edge snapping methods aim at optimizing individual strokes, we show that a co-analysis of multiple nearby, roughly placed strokes better captures the user’s intention. We formulate automatic sketch improvement as a three-level optimization problem and present an efficient solution to it. EZ-Sketching can tolerate user errors from various sources such as indirect control or inherently inaccurate input, and works well for freehand sketching on touch devices with small screens. Similar to the image-driven assistance in EZ-Sketching, our animation assistant tool, Live Sketch, allows novice users to interactively bring static drawings to life by applying deformation-based animation effects that are extracted from video examples. Dynamic deformation is first extracted as a sparse set of moving control points from videos and then transferred to static drawings. Our system addresses several major technical challenges, such as motion extraction from video, video-to-sketch alignment, and many-to-one motion-driven sketch animation. While each of the sub-problems could be difficult to solve fully automatically, we present realtime and reliable solutions by combining new computational algorithms with intuitive user interactions. In addition to improving users’ drawing experience and aesthetics, we also present a target acquisition technique on touch devices, 2D-Dragger, which aims at making the selection of UI elements easier and more accurate for users. Occlusion (small, dense targets) and inaccessibility (out-of-reach targets) are two main problems that may lead to inaccuracy and inefficiency. Our main idea is that the effective width of each object is constant and the same, allowing a fixed scale of finger movement for capturing a new target. Our tool is thus insensitive to the distribution and size of the selectable targets, and consistently and robustly works well for selecting targets with various distributions. With the above three assistant tools, we expect novice users can quickly and painlessly create drawings and animations. To evaluate the effectiveness and robustness of the three techniques, we conduct several user studies for each technique. The results show that our methods allow users without drawing or animation skills to easily create plausible results.

Date of Award	2018
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology