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This article presents a real-time GPU-based post-filtering method for rendering acceptable depth-of-field effects suited for virtual reality. Blurring is achieved by nonlinearly interpolating mipmap images generated from a pinhole image. Major artifacts common in the post-filtering techniques such as bilinear magnification artifact, intensity leakage, and(More)
This paper presents a quantitative characterization of the instability that a human user often experiences while interacting with a virtual textured surface rendered with a force-reflecting haptic interface. First, we quantified the degree of stability/ instability during haptic texture rendering through psychophysical experiments. The stiffness of the(More)
This paper presents a real-time framework for computationally tracking objects visually attended by the user while navigating in interactive virtual environments. In addition to the conventional bottom-up (stimulus-driven) saliency map, the proposed framework uses top-down (goal-directed) contexts inferred from the user's spatial and temporal behaviors, and(More)
This study investigates the effect of update rate on the perceived quality of haptic virtual textures, focusing on one type of perceived instability called "buzzing." Buzzing refers to the high-frequency noises that may emanate from a force-feedback device during haptic texture rendering. We first present a simulation of a haptic texture rendering system(More)
Many virtual reality systems have a distributed structure for certain purposes such as more computational power, tele-presence, collaboration, and portability. However, network delays are inevitable in the distributed structure and often make sensory information delivered behind time to the user. In the literature, the effect of network delays on the(More)
In this paper, we present an experimental study in which we tested the feasibility of a hybrid haptic assistance scheme that combines haptic guidance and disturbance. In our hybrid method, haptic guidance is used in the initial phase of learning, but it is progressively turned into haptic disturbance as the learner's performance improves. The purpose of(More)
The force-constancy hypothesis states that the user of a force-feedback device maintains a constant penetration force when stroking virtual surfaces in order to perceive their topography. The hypothesis was developed to address a real-world data perceptualization problem where the perception of surface topography was distorted when the surface stiffness was(More)