Video Paintbox: The fine art of video painting

We present the Video Paintbox; a novel system capable of transforming video into stylised animations. Our system solves the problem of temporally coherent painting for a wide class of video, and is able to introduce cartoon-like motion emphasis cues. Coherent painting in video is a long-standing problem that is associated with the difficulties in placing, orienting, and sizing paint strokes over time. Our solution allows removal of stroke flicker, allowing animators control over any stylisation and incoherence they might care to re-introduce. Furthermore, the animator can choose to selectively paint certain objects, leaving photorealistic video elsewhere. Many common motion cues used by animators, such as streak-lines, squash-and-stretch, and anticipated movement may be integrated with either real or painted footage. The motion cues depend on a robust analysis of video that allows for effects such as camera motion and occlusion, and which is able to automatically build articulated dolls complete with kinematic properties. We describe our Video Paintbox, discuss animator controls, and illustrate with examples.     

Video motion analysis for the synthesis of dynamic cues and Futurist art

This paper presents new methods for stylising video to produce cartoon motion emphasis cues and modern art. Specifically, we introduce “dynamic cues” as a class of motion emphasis cue, encompassing traditional animation techniques such as anticipation and motion exaggeration. We describe methods for automatically synthesising such cues within video premised upon the recovery of articulated figures, and the subsequent manipulation of the recovered pose trajectories. Additionally, we show how our motion emphasis framework may be applied to emulate artwork in the Futurist style, popularised by Duchamp.     

Rendering cartoon-style motion cues in post-production video

The contribution of this paper is a novel non-photorealistic rendering (NPR) system capable of rendering motion within a video sequence in artistic styles. A variety of cartoon-style motion cues may be inserted into a video sequence, including augmentation cues (such as streak lines, ghosting, or blurring) and deformation cues (such as squash and stretch or drag effects). Users may select from the gamut of available styles by setting parameters which influence the placement and appearance of motion cues. Our system draws upon techniques from both the vision and the graphics communities to analyse and render motion and is entirely automatic, aside from minimal user interaction to bootstrap a feature tracker. We demonstrate successful application of our system to a variety of subjects with complexities ranging from simple oscillatory to articulated motion, under both static and moving camera conditions with occlusion present.     

Volumetric texture synthesis for non-photorealistic volume rendering of medical data

This paper presents a novel technique, called volumetric texture synthesis, for non-photorealistic volume rendering. It extends texture synthesis from 2D areas/3D surfaces to volumes. By selecting different texture samples, it allows for a wide variety of stylized rendering for the target volume. As a preprocessing step, volume data analysis is used to identify texture orientations for the volume. This is followed by volumetric texture synthesis, which generates 3D non-photorealistic textures along the identified texture orientations. Finally, standard volume rendering is applied to display the volume data decorated by the texture. Experimental results are provided in the paper.     

Building blocks for goal-directed motion

An approach for the integration of intelligent goal directed motion within an interactive real-time computer animation environment is sketched. The approach is based on a cause-and-effect model for intelligent goal direction motion which gives rise to types of motion primitives: one is the application of a so called multi-track recording paradigm for direction motion manipulation; the second is an algorithm to mimic a control system for goal directed motion of joints in a multi-link structure. The techniques described here are features of the procedure based animation system which is described in Reference 1.     

Graphical interface for motion editing using procedure visualization

In this paper, we introduce an interface for motion editing that visualizes editing procedures. For intuitive understanding and construction of motion editing procedures, our system represents an editing element that produces modified motion from a given input motion as a graphical node, and enables user to construct a whole motion editing procedure by connecting the nodes with a few mouse interactions. The system provides both the 3D transform manipulator and the time-line slider for intuitive controlling ...     

Constraint-based motion adaptation

Today's computer animators have access to many systems and techniques to author high-quality motion. Unfortunately, available techniques typically produce a particular motion for a specific character. In this paper we present a constraint-based approach to adapt previously created motions to new situations and characters. We combine constraint methods that compute changes to motion to meet specified needs with motion signal processing methods that modify signals yet preserve desired properties of the original motion. The combination allows the adaptation of motions to meet new goals while retaining much of the motion's original quality. © 1998 John Wiley & Sons, Ltd.     

Combining path planners and motion graphs

Natural locomotion of virtual characters is very important in games and simulations. The naturalness of the total motion strongly depends on both the path the character chooses and the animation of the walking character. Therefore, much work has been done on path planning and generating walking animations. However, the combination of both fields has received less attention. Combining path planning and motion synthesis introduces several problems. In this paper, we will identify two problems and propose possible solutions. The first problem is selecting an appropriate distance metric for locomotion synthesis. When concatenating clips of locomotion, a distance metric is required to detect good transition points. We have evaluated three common distance metrics both quantitatively (in terms of footskating, path deviation and online running time) and qualitatively (user study). Based on our observations, we propose a set of guidelines when using these metrics in a motion synthesizer. The second problem is the fact that there is no single point on the body that can follow the path generated by the path planner without causing unnatural animations. This raises the question how the character should follow the path. We will show that enforcing the pelvis to follow the path will lead to unnatural animations and that our proposed solution, which uses path abstractions, generates significantly better animations. Copyright © 2011 John Wiley & Sons, Ltd.     

面向反馈运动控制器的多目标求解

目的 基于物理模拟的人体运动生成方法由于能够合成符合自然规律的运动片段,可实时响应环境的变化,且生成的物理运动不是机械性的重复,因此是近年来计算机动画和虚拟现实领域中最活跃的研究方向之一。然而人体物理模型具有高维、非线性及关节间强耦合性等特点,求解人体物理运动十分困难。反馈控制器常用于人体物理运动控制,求解时通常需要对多个目标函数加权求和,然而权重的设置需多次试验,烦杂耗时。针对运动控制器求解困难的问题,本文提出了一种面向反馈运动控制器的多目标求解方法。方法 首先,对运动数据进行预处理并提取关键帧求解初始控制器,并设计一种改进的反馈控制机制;在此基础上,种群父代个体变异产生子代,采用禁选区域预筛选策略去除不满足约束的个体,并通过重采样获取新解;然后,通过物理仿真获得多目标适应度值,采用区域密度多层取优选取分布均匀的优秀个体作为下一代父代,并通过基于剪枝的多阶段物理求解算法决定是否进入下一阶段优化;经过多次迭代后获得物理控制器,从而生成具有反馈的人体物理运动。结果 针对提出的方法,本文针对多个测试函数和物理运动分别进行实验：在测试函数实验中,本文分别采用经典的测试函数进行实验对比,在相同的迭代次数下,相比之前算法,本文算法中满足约束的优秀个体命中率更高,反转世距离更小,且最优解集的分布更加均匀;物理运动生成实验中,分别针对走路、跑步和翻滚等运动进行物理运动生成,与之前算法进行对比,本文算法可以更早地完成收敛,同时目标函数值更小,表明生成的运动效果更好。结论 本文提出的进化求解方法可以生成不同运动的控制器,该控制器不仅可以生成物理运动,而且还具备外力干扰下保持平衡的能力,解决了运动控制器求解中多目标权重设置困难、优化时间长的问题;除此之外,本文算法还对具有约束的多目标问题具有较好的求解效果。