Chotikakamthorn, Nopporn

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Chotikakamthorn, Nopporn
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Chotikakamthorn, N.
Chotikakamthornb, Nopporn
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nopporn.ch@kmitl.ac.th

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    Item type:Publication,
    Performance of Bayesian-based digital matting techniques
    (2007-12-01)
    Cumpim, Chaipichit
    ;
    Chotikakamthorn, Nopporn
    Statistical-based digital matting of natural background is considered in this paper. Performance of the original Bayesian-based matting method has been studied. It is shown that the performance depends on the algorithm initial condition as well as a noise variance parameter. Two initialization methods have been considered. The first one obtains initial value from Ruzon's maximum likelihood method, while the second one employs the centers of foreground and background color clusters as the initial value. Both methods were found to offer improved performance. In addition, optimum choice of the noise variance was found to vary from one image to another. An alternative formulation of a Bayesian-based digital matting technique which does not contain the noise variance parameter is described. It was found to yield results comparable to the original method for most of the test cases. ©2007 IEEE.
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    Fast haptic simulation of brittle object using bounded force propagation model
    (2008-12-01)
    Somrang, Nontapol
    ;
    Chotikakamthorn, Nopporn
    ;
    Jirapatehandej, Siraset
    In this paper, a method for real-time simulation of brittle object with haptic force feedback is described. Based on the rigid-constraint model, originally developed for visual-only image synthesis, a virtual object is represented as a set of point- masses connected by distance-preserving linear constraints. The drawback of the original method is that it is time consuming and not suitable for real-time haptic simulation. In this paper, a bounded force propagation model is developed to reduce calculation time as required by the original method. In addition, a haptic-endpoint position prediction method is applied to prepare the simulation system for the calculation required by the method. These refinements allow the brittle object simulation method to be applicable to real-time interactive applications with haptic force feedback. © 2008 IEEE.
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    Weighted hough transform for directional light sources estimation from multi-view images
    (2012-12-01)
    Bunteong, Anusorn
    ;
    Chotikakamthorn, Nopporn
    An improved method for light sources estimation from shading is proposed in this paper. This method indicates the advantage of multi-view images rather than single view image. Even though there are several methods that can be used to estimate light sources from single view image, data from single view may be not accurate for all light source estimations. The shading on a Lambertian surface sphere is used to detection critical paths and the directions of directional light sources can be estimated from these paths. Hough Transform is used to find critical paths from critical points in images. Rather than using the standard Hough Transform, we improve vote count processes by determining a weight value for each critical point in Hough space. Weight values are calculated from angles between surface normal at each critical point and view vector from cameras. The experimental results demonstrate that the proposed method with information obtained from multi-view images yields better performance than the method with a single-view image.
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    Using Mozilla Hubs for Online Teaching: A Case Study of An Innovation Design Method Course
    (2023-01-01)
    Poolsawas, Banyapon
    ;
    Chotikakamthorn, Nopporn
    During the Covid-19 pandemic, video conferencing platforms such as Zoom Online, MS Team Meeting, and Google Meets have been primary remote teaching tools. 3D immersive and non-immersive social platforms such as Mozilla Hubs have been studied as alternative tools for organizing remote teaching. This study aimed to assess the usability of Mozilla Hubs when applied to remote teaching and compared it to that of the widely used Zoom platform. An undergraduate course on innovation design methods was selected as the case study. Students enrolled in this course were divided into two groups. Distance learning was conducted through the Zoom platform for the first group of students. In contrast, the other group participated in the course activities through the Mozilla Hub platform within a non-immersive setting. The students in the Hubs group were requested to participate in the Hub pre-training class a week before the first week of the course's lecture. Six everyday tasks requiring student interaction with each of the two platforms were selected for the study. Usability was measured in terms of efficiency and ease of use. The time taken to complete each of the selected tasks was used to measure the efficiency of each platform. The System Usability Scale (SUS) questionnaire was used to measure ease of use. For most tasks, both platforms yielded comparable results regarding task efficiency. The only exception is for the room transition task, where the results differed between the two platforms depending on whether the teleport or 3D navigation methods were chosen by students in the Hubs group in order to complete the task. Discussion on the factors affecting the efficiency of the room transition task was provided. Using the SUS questionnaire, it was found that both platforms yielded comparable SUS scores of 68.91 and 70.66 for the Zoom and Mozilla Hubs platforms, respectively. Similar ease-of-use results were due to the offering of the Hubs pre-training class to the students using the Mozilla Hubs platform.
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    Evaluation the efficacy of Computer - Based training using tangible user interface for Low-Function children with autism
    (2008-12-01)
    Sitdhisanguan, Karanya
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    Chotikakamthorn, Nopporn
    ;
    Dechaboon, Ajchara
    ;
    Out, Patcharaporn
    Recently, the number of children having autism disorder increases rapidly all over the world. Computerbased training (CBT) has been applied to autism spectrum disorder treatment. Most CBT applications are based on the standard WIMP interface. However, recent study suggests that a Tangible User Interface (TUI) is easier to use for children with autism than the WIMP interface. In this paper, the efficiency of the TUI training system is considered, in comparison with a conventional method of training basic geometric shape classification. A CBT system with TUI was developed using standard computer equipment and a consumer video camera. The experiment was conducted to measure learning efficacy of the new system and the conventional training method. The results show that, under the same time constraint, children with autism who practiced with the new system were able to learn more shapes than those participating in the conventional method. © 2008 IEEE.
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    Comparative study of two projective-invariant digital watermarking methods using cross-ratios and line intersections
    (2005-12-01)
    Pantuwong, Natapon
    ;
    Chotikakamthorn, Nopporn
    Recently, based on a set of four coplanar points, a projective-invariant digital watermarking has been developed. A combination of line intersection and the cross-ratio relationship of collinear points is used to calculate watermarking embedding locations. The four coplanar points used to derive embedding locations can be obtained from either the image corners or the feature points extracted from the image content. It is shown in this paper that based on the same principle, an alternative algorithm for calculating the watermark embedding locations improves computational efficiency. The proposed method heavily uses the cross-ratio relationship of collinear points, while minimizing the use of line intersection in obtaining embedding locations. This is in contrast with the original method, where embedding locations are mainly obtained from intersections of line pairs. Both analytical and experimental results are provided to demonstrate the improvement. © 2005 IEEE.
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    Evaluation of mobile phone interaction with large public displays
    (2017-09-05)
    Pattanakimhun, Patchara
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    Chinthammit, Winyu
    ;
    Chotikakamthorn, Nopporn
    Large public displays are widely used in public spaces for serving information. The flow of the information is largely a one-way passive communication due to a lack of user-content interaction, which in some ways limits its effectiveness as an information display system. We propose a use of mobile phones as a tool to interact with a public display. Our proposed mobile-public display user interaction uses a mobile phone to control and retrieve information from a public display. In this paper we present results of a usability test of our proposed interaction, which indicated that there was a strong correlation between the information retrieval performances and the participant's level of engagement with the mobile phone.
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    A light-pointing method for virtual object selection and manipulation in a monoscopic viewing system
    (2005-12-01)
    Kanjanasupark, Pornchai
    ;
    Chotikakamthorn, Nopporn
    Virtual object selection and re-location are two basic object manipulations that can be found in most VR/VE applications. Many interaction metaphors have been developed for object manipulation in VR/VE environments. Of particular interest is the ray-casting method. The method applies a light ray metaphor in selecting and moving a virtual object. However, the method implicitly requires a stereoscopic viewing system to be efficiently use. With a monoscopic viewing system, inefficiency of the method in terms of task completion time is demonstrated in this paper. For a system using a monoscopic viewing device, a light-pointing method based on a laser-pointer metaphor is proposed to alleviate the shortcoming of the original ray-casting method. Compared with the ray-casting method, it was found from the experiment that the proposed method is noticeably more efficient in terms of task completion time. © 2005 IEEE.
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    Interactive public display using mobile web client
    (2017-07-01)
    Pattanakimhun, Patchara
    ;
    Chotikakamthorn, Nopporn
    ;
    Chinthammit, Winyu
    Large public displays are widely used in public spaces for serving information. Most of them lack user-content interaction due partly to the fact that a touch screen is not suitable. With nearly universal adoption of mobile smartphone devices worldwide, its use as a tool for interacting with a public display is a viable option. Lack of standard interaction methods, protocols, and wide-spread used mobile applications for this purpose is a problem that prevents its adoption. In this paper, we address these problems by proposing a method with a mobile phone device as a tool for interaction with a public display system. The method is based on a standard web client, preinstalled on all smartphone devices, thus avoiding the problem as mentioned. Standard mobile gestures were employed for ease of use. The problem of establishing a connection and getting control of the public display is addressed. Three pairing methods have been described and evaluated. The results and discussion are provided.
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    An interatvie stereoscopic viewing system using fast vision-based leg end-point position estimation
    (2005-12-01)
    Phutphuek, Narongsak
    ;
    Chotikakamthorn, Nopporn
    In this paper, a problem of interactive stereoscopic display is considered. To provide a stereo image pair with correct viewing angle, a stereoscopic system must be able to identify a viewer spatial location. A fast and low-cost viewer location estimation method using a single video camera is described in this paper. The method tracks a viewer's standing position by estimating his/her leg end-point on the floor. The so-obtained position is then transformed to a 3D coordinate by using a planar homographic projection. Because the estimated viewer position is noisy, a smoothing and semi-interactive updating algorithm is developed to reduce a flicker caused by the imprecise estimate. © 2005 IEEE.