Browsing by Author "Wong, Sai-Keung"

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A Framework for Simulating Agent-Based Cooperative Tasks in Crowd Simulation
(2018-01-01)
Wong, Sai-Keung
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Chou, Yi-Hung
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Yang, Hsiang-Yu
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資訊工程學系
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Department of Computer Science
This paper presents a novel agent-based approach to simulate cooperative tasks in crowd simulation. Our framework consists of two kinds of agents: pedestrians and workers. A cooperative task requires two or more workers to simultaneously perform actions on objects. The workers should cooperate with each other to finish tasks. This framework considers several basic cooperative behaviors including pushing obstacles away from blocked exits, lifting cargos and carrying them to a destination, and pulling objects using ropes. A complex task can be decomposed into several simple tasks and the simple tasks are finished either in a sequential or parallel order. Our framework also simulates crowd behaviors such as workers joining and leaving cooperative tasks, moving objects around obstacles, collision avoidance for agents, and way giving. We demonstrate examples for simulating different cooperative behaviors. Our framework can be applied to movies, crowd evacuation, narrative systems, task planning simulation, and games.
A heuristic approach to the simulation of water drops and flows on glass panes
(2013-12-01)
Chen, Kai-Chun
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Chen, Pei-Shan
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Wong, Sai-Keung
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交大名義發表
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National Chiao Tung University
Water drops and water flows exhibit interesting motion behavior. In this paper, we adopt a simple but effective approach for simulating this behavior on glass panes in a physically plausible manner. We combine a particle system and a height map to compute their movements and shapes. Our approach efficiently handles the merging of water drops and the formation of residual water droplets. We report our results for several examples of water behavior simulated in real time. The experimental results show that our system simulates water drops and water flows with high quality. (C) 2013 Elsevier Ltd. All rights reserved.
A natural language interface with casual users for crowd animation
(1970-01-01)
Liu, Wen-Yun
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Wong, Sai-Keung
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Chen, Chien-Yuan
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資訊工程學系
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Department of Computer Science
We develop an interface that bridges crowd simulation and natural language processing techniques so that casual users can produce crowd animation by text input. The interface adopts a parser and a tagger to analyze simple English sentences to convert them into intermediate data structures that encapsulate the essential elements of crowds. There are five stages: preprocessing, parsing input sentences, crowd generation, animation adjustment, and crowd animation. Our system supports basic behaviors including standing, walking, running, escaping, being attracted, and queuing. We conducted a user experience study to evaluate the interface. The results show that the interface is user-friendly for casual users to produce crowd animation.
A Procedural Approach to Modelling Virtual Climbing Plants With Tendrils
(2016-12)
Wong, Sai-Keung
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Chen, Kai-Chun
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資訊工程學系
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Department of Computer Science
Climbing plants with tendrils show search and coiling behaviour. A tendril searches for a host object and then twines around it. Subsequently, the tendril coils to pull the main stem of the climbing plant close to the host object. Furthermore, the stems may also twine around the host object. In this paper, we propose a procedural approach to incrementally constructing virtual climbing plants with tendrils that mimic such behaviour. We developed several simple rules to guide the construction process. Although our approach is not based on a physical or biological concept, it is fast and efficient in generating climbing plants with tendrils, with acceptable quality. We propose techniques that are useful for enhancing the realism of climbing plants in close-up view.
A Skeleton-Based Approach for Consistent Segmentation Transfer
(2014-07-01)
Wong, Sai-Keung
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Yang, Jau-An
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Ho, Tan-Chi
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Chuang, Jung-Hong
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資訊工程學系
We present a skeleton-based approach for mapping consistently a segmentation of a source mesh to a target mesh. The source and target meshes are semantically similar but their geometries may be different. We assume that the segmentation of the source mesh and the skeleton correspondence between the meshes are provided. Our method first establishes the skeleton-boundary correspondence and then performs the boundary transfer procedure. The skeleton-boundary correspondence is useful for computing approximately the target boundaries. The boundary transfer procedure aims to produce the segment boundaries of the target mesh such that their geometric details are consistent to the ones of the corresponding source segment boundaries. We have applied our method for various models and compared with the state-of-the-art techniques. Our method computes segment boundaries of the target mesh which are similar to the ones of the source mesh.
A Study on Genetic Algorithm and Neural Network for Implementing Mini-Games
(2010-01-01)
Charoenkwan, Phasit
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Fang, Shih-Wei
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Wong, Sai-Keung
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資訊工程學系
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Department of Computer Science
We study on artificial neural network-based controllers which are either trained or evolved by using the supervised or unsupervised learning approach. We employed backpropagation for the supervised method and the genetic algorithm for the unsupervised method. After training the controllers, we applied the controllers to our three newly designed mini-3D games. We performed a comprehensive study on the performance and weaknesses of the controllers. We emerged the controllers as fundamental tools for giving us more understanding about artificial neural network and its effectiveness in imitating players' behaviours.
A Study on Genetic Algorithm and Neural Network for Mini-Games
(2012-01-01)
Wong, Sai-Keung
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Fang, Shih-Wei
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資訊工程學系
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Department of Computer Science
Physics simulation and character control are two important issues in computer games. In this paper, we propose two games which are tailored for investigating some aspects of these two issues. We study on the applications of neural network and the genetic algorithm techniques for building the controllers and the controllers should be able to finish the specific tasks in the two games. The goal of the first game is that the controller can shoot a ball so that the ball collides with the other two balls one after another. The challenge of this game is that the ball should be shot from the proper position and the goal is achieved every time. The second game is a duel game and two virtual characters are controlled to fight with each other. We develop a method for verifying whether or not the skill power of the two virtual characters is balanced. The controllers of both games are evolved based on neural network and genetic algorithm in an unsupervised learning manner. We perform a comprehensive study on the performance and weaknesses of the controllers.
A Two-Dimensional Editing System Based on Hand Gestures and Real Object Manipulation Using RGB-D Sensor
(2016-01-01)
Chen, Hsin-Kai
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Wong, Sai-Keung
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Huang, Po-Han
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Chang, Yu-An
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交大名義發表
This paper presents a two-dimensional editing system which compromises the advantages of using hand gestures and real blocks to manipulate virtual objects. The system uses a RGB-D sensor to capture the color and depth images of the hands and real blocks. The raw images of the hands and blocks are segmented. Then we employ a contour based algorithm to perform hand gesture and shape recognition. The contours are extracted and reduced for eliminating the redundant points. After that a set of feature points are collected and they can be used for recognizing the hand gesture and the shapes of the real blocks. The users have two ways to interact with the virtual objects: 1) manipulating the real blocks to control them; and 2) using hand gestures as editing operations to edit them. Experimental results indicate that our system achieves high recognition rate. Our system supports the basic editing operations to the virtual objects, such as 'move', 'scale', 'rotate', and 'copy'. We also conducted a user study which reveals that our system is intuitive and entertaining.
Adaptive Continuous Collision Detection for Cloth Models Using a Skipping Frame Session
(2011-09-01)
Wong, Sai-Keung
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資訊工程學系
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Department of Computer Science
We propose a novel adaptive pipeline for continuous collision detection in cloth simulation. The pipeline consists of four components: bounding volume hierarchy (BVH) update, BVH traversal, a skipping frame session, and elementary test processing. The skipping frame session is activated adaptively for skipping both BVH update and BVH traversal during the process of collision detection. The proposed method improves the performance of collision detection in simulating cloth models comparing to some existing feature-based collision detection techniques, as indicated from experimental results.
Adversarial Colorization Of Icons Based On Structure And Color Conditions
(2019-01-01)
Sun, Tsai-Ho
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Lai, Chien-Hsun
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Wong, Sai-Keung
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Wang, Yu-Shuen
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交大名義發表
We present a system to help designers create icons that are widely used in banners, signboards, billboards, homepages, and mobile apps. Designers are tasked with drawing contours, whereas our system colorizes contours in different styles. This goal is achieved by training a dual conditional generative adversarial network (GAN) on our collected icon dataset. One condition requires the generated image and the drawn contour to possess a similar contour, while the other anticipates the image and the referenced icon to be similar in color style. Accordingly, the generator takes a contour image and a man-made icon image to colorize the contour, and then the discriminators determine whether the result fulfills the two conditions. The trained network is able to colorize icons demanded by designers and greatly reduces their workload. For the evaluation, we compared our dual conditional GAN to several state-of-the-art techniques. Experiment results demonstrate that our network is over the previous networks. Finally, we will provide the source code, icon dataset, and trained network for public use.
Animating Agents Based on Radial View in Crowd Simulation
(2016)
Li, Fu-Shun
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Wong, Sai-Keung
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交大名義發表
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National Chiao Tung University
We present a simple agent-based approach for crowd simulation in a two-dimensional space. Our approach computes a set of collision-free feasible movement directions for each agent. The movement directions of the agent are determined according to a radial view of the agent in the local region. Subsequently, the direction with the least effort is selected for moving the agent. To efficiently compute feasible movement directions for each agent, we discretize the movement direction field of the agent and use a bit string to estimate the set of movement directions. Each bit of the bit string represents a span of movement directions. The proposed approach enables the agents to move around simple objects without using expensive global search techniques. Experimental results show that our approach can simulate agents that can alleviate the collision problem. The agents can move to their destinations efficiently.
ANIMATING PICTURES USING PROCEDURAL 2.5D WATER FLOW SIMULATION
(2017-01-01)
Sun, Tsai-Ho
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Tseng, Yi-Chun
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Wong, Sai-Keung
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Chen, Hsuan
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Tsai, Tsung-Yu
In this paper, we present a procedural 2.5D water flow simulation technique to animate pictures. For a given picture, we convert it into a 2.5D structure and then perform water simulation for the 2.5D structure (like a shallow-relief sculpture). The proposed approach is divided into three phases: image processing, water simulation and rendering. First, we extract the objects in the picture and compute their 2.5D structure based on image processing techniques. Second, a procedural based approach is adopted to simulate water flows over the 2.5D structure. Finally, we apply a simple ray tracer to render final images. Experimental results show that the simulated water flows naturally over the 2.5D structure of the pictures at real time rates. We also printed out the 2.5D structures of the virtual objects as 3D models for visual comparison.
Continuous collision detection for deformable objects using permissible clusters
(2015-04-01)
Wong, Sai-Keung
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Baciu, George
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交大名義發表
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National Chiao Tung University
In this paper, we propose a new data structure to perform continuous collision detection (CCD) for deformable triangular meshes. The critical component of this data structure is permissible clusters. At the preprocessing phase, the triangular meshes are divided into permissible clusters. Then, the features of the triangular meshes are assigned to the permissible clusters. At the runtime phase, the potentially colliding feature pairs are collected and they are processed only once in the elementary processing. Our method has been integrated with a normal cone-based method and compared with other CCD methods. Experimental results show that our method improves the overall performance of CCD for deformable objects.
Continuous Self-Collision Detection for Deformable Surfaces Interacting with Solid Models
(2014-09-01)
Wong, Sai-Keung
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Cheng, Yu-Chun
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交大名義發表
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National Chiao Tung University
In this paper, we propose a new continuous self-collision detection (CSCD) method for a deformable surface that interacts with a simple solid model. The method is developed based on the radial-view-based culling method. Our method is suitable for the deformable surface that has large contact region with the solid model. The deformable surface may consist of small round-shaped holes. At the pre-processing stage, the holes of the deformable surface are filled with ghost triangles so as to make the mesh of the deformable surface watertight. An observer primitive (i.e. a point or a line segment) is computed so that it lies inside the solid model. At the runtime stage, the orientations of triangles with respect to the observer primitive are evaluated. The collision status of the deformable surface is then determined. We evaluated our method for several animations including virtual garments. Experimental results show that our method improves the process of CSCD.
Digital Artwork Creation Using Water and Sand on a Two-Dimensional Surface
(2015)
Chen, Ting-Yu
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Wong, Sai-Keung
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交大名義發表
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National Chiao Tung University
In this paper, we developed a system which enables users to draw pictures of sand and water on a two-dimensional surface in a virtual environment. By mixing water and sand for artwork creation, we can create different styles of pictures. Our system has three major subsystems: water animation system, sand animation system and rendering system. In the simulation part, we compute the motion of sand and water based on the interactions for water-water, sand-water and sand-sand. In the rendering part, we attempt to balance the rendering quality and the computation cost. We render water using a ray tracing method and the sand is rendered with shadow. Thus, the rendered results of water and sand look like 2.5D. We tested our system and the experimental results showed that the users could create a variety of pictures of sand and water.
Directing virtual crowds based on dynamic adjustment of navigation fields
(2018-01-01)
Tsai, Tsung-Yu
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Wong, Sai-Keung
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Chou, Yi-Hung
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Lin, Guan-Wen
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交大名義發表
Navigation fields are a popular data structure for directing the movement of virtual crowds. However, the congestion problem may occur at the corners of objects in using a navigation field because the agents move quite closely to each other. The agents may congest at the corners even though there is room for the agents to move away from the congested regions. In this paper, we propose to place crowd monitors at the corners to collect the data such as the movement direction of crowds and crowd densities. Then the navigation field is adjusted dynamically so that the crowds are led to move away from the congested regions. We also propose a simple data structure for speeding up the collision detection process between agents and objects. Experimental results show that our approach successfully alleviates the congestion problem at the corners.
Effects of Interacting with a Crowd of Emotional Virtual Humans on Users' Affective and Non-Verbal Behaviors
(2020-01-01)
Volonte, Matias
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Hsu, Yu-Chun
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Liu, Kuan-Yu
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Mazer, Joe P.
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Wong, Sai-Keung
In this contribution we examined the effects on users during interaction with a virtual human crowd in an immersive virtual reality environment. We developed an agent-based crowd model with rich properties including eye gaze, facial expression, body motion, and verbal and non-verbal behaviors. The scenario was a virtual market in which the users needed to gather specific items. In a between subjects design, users interacted with a virtual human crowd that showed opposite valenced emotional expressions. There are four conditions in the between-subjects design. These includes different affective virtual crowds namely, Positive, Negative, Neutral, and a Mix condition. The Mix group is defined by a combination of Positive, Negative and Neutral emotional expressive characters. Depending on the specific condition, the virtual humans showed specific verbal and non-verbal behaviors. During the experiment we collected objective measures such as skin electrodermal activity, total time in the simulation, the number of interactions with the agents and performance measures. The subjective measures were the differential emotional survey (DES), and a user experience survey. We reported our findings with an in-depth analysis.
Effects of Reward Terms in Agent-Based Box-Manipulation Animation Using Deep Reinforcement Learning
(2019-01-01)
Yang, Hsiang-Yu
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Wong, Chien-Chou
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Wong, Sai-Keung
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資訊工程學系
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電機學院
Agent-based box manipulation has wide applications in computer animation and robotics. Deep reinforcement learning can be applied to generate animations of agent-based box manipulation. This paper focuses on push-manipulation in an agent-based animation. A policy is learned in a learning session in which an agent receives a reward that is a combination of different types of reward terms. Based on the received reward, the policy is improved gradually. In this paper, we investigate the effects of each reward term in-depth in a framework that is integrated with deep reinforcement learning. We also propose a simple way to produce different animation types. We performed several examples and analyzed our findings in details.
Emotional virtual crowd on task completion in virtual markets
(2018-05-01)
Huang, Po-Han
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Wong, Sai-Keung
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資訊工程學系
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Department of Computer Science
This paper studies the effects of a virtual crowd with emotion on task completion in a virtual market. The users have to interact with the virtual agents so that the virtual agents are willing to lead the users to specific vendors. Then, the users can buy the required items. The users communicate with the virtual agents via a conversation dialog. The emotional agents' moods are affected by their own interaction (e.g., collision) while they are walking. Furthermore, their moods are also affected by the conversational responses of the users. We adopt a simple 2D mood model and use icons to represent the mood states of the agents. The mood model supports four mood states, which are Excitement, Anger, Sadness, and Neutral. We conducted a user study to evaluate the effects of the emotional virtual agents in different aspects, including task completion, time spent in conversation, following distance, and realism of the emotional virtual crowd.
Evacuation simulation with consideration of obstacle removal and using game theory
(2018-06-05)
Lin, Guan-Wen
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Wong, Sai-Keung
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資訊工程學系
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Department of Computer Science
In this paper, we integrate a cellular automaton model with game theory to simulate crowd evacuation from a room with consideration of obstacle removal. The room has one or more exits, one of which is blocked by obstacles. The obstacles at the exit can be removed by volunteers. We investigate the cooperative and defective behaviors of pedestrians during evacuation. The yielder game and volunteer's dilemma game are employed to resolve interpedestrian conflict. An anticipation floor field is proposed to guide the pedestrians to avoid obstacles that are being removed. We conducted experiments to determine how a variety of conditions affect overall crowd evacuation and volunteer evacuation times. The conditions were the start time of obstacle removal, number of obstacles, placement of obstacles, time spent in obstacle removal, strength of the anticipation floor field, and obstacle visibility distance. We demonstrate how reciprocity can be achieved among pedestrians and increases the efficiency of the entire evacuation process.