Catálogo de publicaciones - libros

Terrain texture plays a great role on visualization in many 3D applications. Sometimes terrain texture is difficult to obtain in a desired area, thus a new approach to terrain texture generation based on satellite images is proposed to resolve this problem. We prepare a silhouette map and a satellite image for the desired terrain texture and colorize the two pictures with the same pattern according to the terrain features. Then a method of texture synthesis is adopted to generate the final terrain texture.

A navigation system for virtual environments using low-quality HMD(head mounted display) must quantize images when the system presents true-color image with restricted number of colors. Such navigation system quantizes an image by using fixed palette. If the system represents an image by using a variable palette which is made considering a region around the viewpoint then user can perceive a virtual environments more vividly because human visual system is sensitive to the colors variation in the region around the viewpoint. In this paper we propose a color quantization algorithm that quantize a region around the viewpoint more finely than other regions at each variation of viewpoint for virtual environments navigation system and compose virtual environments navigation system using proposed algorithm. The system quantizes an image at each variation of viewpoint and shows a quantized image to user through HMD. We tested user preferences for our proposed system and the results show that users preferred our system.

Emerging applications in the area of Emergency Response and Disaster Management are increasingly demanding interactive capabilities to allow for the quick understanding of a critical situation, in particular in urban environments. A key component of these interactive simulations is how to recreate the behavior of a crowd in real- time while supporting individual behaviors. Crowds can often be unpredictable and present mixed behaviors such as panic or aggression, that can very rapidly change based on unexpected new elements introduced into the environment. We present preliminary research specifically oriented towards the simulation of large crowds for emergency response and rescue planning situations. Our approach uses a highly scalable architecture integrated with an efficient rendering architecture and an immersive visualization environment for interaction. In this environment, users can specify complex scenarios, “plug-in” crowd behavior algorithms, and interactively steer the simulation to analyze and evaluate multiple “what if” situations.

To preserve appearance attributes in a 3D model, a novel mesh simplification is proposed in this work based on the Quadric Error Metric (QEM). We make use of half-edge collapse method for mesh simplification and modify the QEM to solve the break between different texture coordinates. After analyzing several cases of the collapsing operation, a new formula on the cost of edge contraction is obtained to eliminate aberrances. Experimental results demonstrate that compared with other state-of-the-art techniques our algorithm can achieve satisfactory efficiency with desirable geometry and feature-preserving.

In direct-projected augmented reality, the visual patterns for compensation may distract users despite users would not be interested in the compensation process. The distraction becomes more serious for dynamic projection surface in which compensation and display should be done simultaneously. Recently, a complementary pattern-based method of efficiently hiding the compensation process from users’ view has been proposed. However, the method faced the tradeoff between the pattern imperceptibility and compensation accuracy. In this paper, we embed locally different strength of pattern images into different channels of the projector input images (AR images) after analyzing their spatial variation and color distribution. It is demonstrated that our content adaptive approach can significantly improve the imperceptibility of the patterns and produce better compensation results by comparing it with the previous approach through a variety of experiments and subjective evaluation.

The development of lower cost modular spatially immersive visualization systems based on commodity components and faceted display surfaces is described. Commodity computers are networked to form graphics computing clusters. Commodity digital projectors are used to form surrounding rear projected faceted display surfaces based on polyhedral shapes. The use of these systems in the design and evaluation of human environments is discussed.

In some collaborative manipulation activities – for example, medical experts making a diagnosis based on a 3D reconstruction of a human organ – remote participants may tailor their views on the shared object to their particular needs and task. This implies that each user has her viewpoint on the object. Awareness of viewpoint is then necessary both to coordinate each other and to understand remote users’ activities. This work investigates how to provide the remote viewpoint awareness in a 3D collaborative desktop in which multiple shared objects can be independently positioned and manipulated to accomplish a common single activity. Preliminary results of ergonomic evaluations of the proposed metaphors are also provided.

We propose a hybrid algorithm – (Parallel Search Algorithm) between PSO and simplex methods to approximate optimal solution for the Geometric Constraint problems. Locally, simplex is extended to reduce the number of infeasible solutions while solution quality is improved with an operation order search. Globally, PSO is employed to gain parallelization while solution diversity is maintained. Performance results on Geometric Constraint problems show that Parallel Search Algorithm outperforms existing techniques.

Realism is a key goal of most VR applications. As graphics computing power increases, new techniques are being developed to simulate important aspects of the human visual system, increasing the sense of ‘immersion‘ of a participant in a virtual environment. One aspect of the human visual system, depth cueing, requires accurate scene depth information in order to simulate. Yet many of the techniques for producing these effects require a trade-off between accuracy and performance, often resulting in specialized implementations that do not consider the need to integrate with other techniques or existing visualization systems. Our objective is to develop a new technique for generating depth based effects in real time as a post processing step performed on the GPU, and to provide a generic solution for integrating multiple depth dependent effects to enhance realism of the synthesized scenes. Using layered fog as an example, our new technique performs per pixel scene depth reconstruction accurately for the evaluation of fog integrals along line-of-sight. Requiring only the depth buffer from the rendering processing as input, our technique makes it easy to integrate into existing applications and uses the full power of the GPU to achieve real time frame rates.

To evaluate the effects of visually-induced motion sickness that induces symptoms related to the autonomic nervous activity, we proposed a new method for obtaining the physiological index , which represents the maximum cross-correlation coefficient between blood pressure and heart rate, with measurement of neither continuous blood pressure nor ECG but using finger photoplethysmography only. In this study, a blood pressure-related parameter was obtained using the independent component analysis of finger photoplethysmography. Two experimental trials in which subjects performed the Valsalva maneuver and then they watched a swaying video image were carried out to evaluate the adequacy of the proposed method. The experimental results have shown that the proposed method worked successfully as well as the conventional method.