Elastic materials often invite the direct touch of users. It is an open question how seeing elastic materials invokes touch desire. The present study proposes a novel visual feature that modulates apparent elasticity and touch desire. The stimulus for our experiment was a clip in which a computer-rendered elastic surface was indented by a needle-like bar. The features of this stimulus that we focused on were spatial deformation range and indentation depth. Observers rated the following three impressions: apparent elasticity, touch desire, and anticipated touch pleasantness. The results showed that both apparent elasticity and touch desire peaked in the middle of the spatial deformation range. The two impressions also depended on indentation depth and were highly correlated with each other. Anticipated touch pleasantness showed a different peak tendency than the other two. An additional block showed that the deformation realism was not related to the above three impressions. The results suggest that apparent elasticity eliciting touch desire can be determined in the parameter space defined by the spatial deformation range and the indentation depth.

Feedback on the material properties of a visual object is essential in enhancing the users' perceptual experience of the object when users control the object with touchless inputs. Focusing on the softness perception of the object, we examined how the effective distance of hand movements influenced the degree of the object's softness perceived by users. In the experiments, participants moved their right hand in front of a camera which tracked their hand position. A textured 2D or 3D object on display deformed depending on the participant's hand position. In addition to establishing a ratio of deformation magnitude to the distance of hand movements, we altered the effective distance of hand movement, within which the hand movement could deform the object. Participants rated the strength of perceived softness (Experiments 1 and 2) and other perceptual impressions (Experiment 3). A longer effective distance produced a softer impression of the 2D and 3D objects. The saturation speed of object deformation due to the effective distance was not a critical determinant. The effective distance also modulated other perceptual impressions than softness. The role of the effective distance of hand movements on perceptual impressions of objects under touchless control is discussed.

A recently developed light projection technique can add dynamic impressions to static real objects without changing their original visual attributes such as surface colors and textures. It produces illusory motion impressions in the projection target by projecting gray-scale motion-inducer patterns that selectively drive the motion detectors in the human visual system. However, with this technique, determining the best deformation sizes is often difficult: When users try to add a large deformation, the deviation in the projected patterns from the original surface pattern on the target object becomes apparent. Therefore, to obtain satisfactory results, they have to spend much time and effort to manually adjust the shift sizes. Here, to overcome this limitation, we propose an optimization framework that adaptively retargets the displacement vectors based on a perceptual model. The perceptual model predicts the subjective inconsistency between a projected pattern and an original one by simulating responses in the human visual system. The displacement vectors are adaptively optimized so that the projection effect is maximized within the tolerable range predicted by the model. In the research demonstration, we will present a demo tool that incorporates our optimization technique, where a user can interactively edit dynamic appearances of a real object without cumbersome manual adjustments of deformation sizes.

A cast shadow is one of the visual features that serve as a perceptual cue to the three-dimensional (3D) layout of objects. Although it is well known that adding cast shadows to an object produces the illusion that the object has a 3D layout, investigations into this illusion have been limited to virtual objects in a display. Using a light-projection technique, we show that it is possible to create a similar 3D layout illusion for real two-dimensional objects. Specifically, we displayed spatial patterns that look like cast shadows in the vicinity of an object depicted as a printed image. The combination of the cast shadow patterns with the printed object made it appear as if the printed object hovered over its original location even though the object was physically two-dimensional. By using this technique, we demonstrated that the shadow-induced layout illusion resulted in printed images having novel perceptual transparency. Vision researchers may find our technique useful if they want to extend their studies on the perception of cast shadows and transparency with real objects.

A recently developed light projection technique can add dynamic impressions to static real objects without changing their original visual attributes such as surface colors and textures. It produces illusory motion impressions in the projection target by projecting gray-scale motion-inducer patterns that selectively drive the motion detectors in the human visual system. Since a compelling illusory motion can be produced by an inducer pattern weaker than necessary to perfectly reproduce the shift of the original pattern on an object's surface, the technique works well under bright environmental light conditions. However, determining the best deformation sizes is often difficult: When users try to add a large deformation, the deviation in the projected patterns from the original surface pattern on the target object becomes apparent. Therefore, to obtain satisfactory results, they have to spend much time and effort to manually adjust the shift sizes. Here, to overcome this limitation, we propose an optimization framework that adaptively retargets the displacement vectors based on a perceptual model. The perceptual model predicts the subjective inconsistency between a projected pattern and an original one by simulating responses in the human visual system. The displacement vectors are adaptively optimized so that the projection effect is maximized within the tolerable range predicted by the model. We extensively evaluated the perceptual model and optimization method through a psychophysical experiment as well as user studies.

When a conventional stereoscopic display is viewed without stereo glasses, image blurs, or 'ghosts', are visible due to the fusion of stereo image pairs. This artifact severely degrades 2D image quality, making it difficult to simultaneously present clear 2D and 3D contents. To overcome this limitation (backward incompatibility), here we propose a novel method to synthesize ghost-free stereoscopic images. Our method gives binocular disparity to a 2D image, and drives human binocular disparity detectors, by the addition of a quadrature-phase pattern that induces spatial subband phase shifts. The disparity-inducer patterns added to the left and right images are identical except for the contrast polarity. Physical fusion of the two images cancels out the disparity-inducer components and makes only the original 2D pattern visible to viewers without glasses. Unlike previous solutions, our method perfectly excludes stereo ghosts without using special hardware. A simple algorithm can transform 3D contents from the conventional stereo format into ours. Furthermore, our method can alter the depth impression of a real object without its being noticed by naked-eye viewers by means of light projection of the disparity-inducer components onto the object's surface. Psychophysical evaluations have confirmed the practical utility of our method.

Taking advantage of computer graphics technologies, recent psychophysical study on material perception has revealed how human vision estimates the mechanical property of objects, such as liquid viscosity, from image features. Here we consider how human perceive another important mechanical material property --- elasticity. We simulated scenes in which a transparent cube falling on the floor, while manipulating the elasticity of the cube. We asked observers to rate the elasticity using a 5-point scale. Human observers were quite sensitive to the change in the simulated elasticity of the cube. In comparison with the original condition, the elasticity was overestimated when only the cube contour deformation was visible, whereas underestimated when the cube contour deformation was hidden and only internal optical deformation was visible. The effects of contour and optical deformations on elasticity rating were almost the same when the observers viewed white noise fields that reproduced the optical flow fields of the cube movies. Increasing frame duration (which decreased image speed) also increased the apparent elasticity. These results suggest that human elasticity judgment is based on the pattern of image motion arising from contour and optical deformations. This scientific finding may provide a hint for computationally efficient rendering of perceptually realistic dynamic scenes.

Light projection is a powerful technique that can be used to edit the appearance of objects in the real world. Based on pixel-wise modification of light transport, previous techniques have successfully modified static surface properties such as surface color, dynamic range, gloss, and shading. Here, we propose an alternative light projection technique that adds a variety of illusory yet realistic distortions to a wide range of static 2D and 3D projection targets. The key idea of our technique, referred to as (Deformation Lamps), is to project only dynamic luminance information, which effectively activates the motion (and shape) processing in the visual system while preserving the color and texture of the original object. Although the projected dynamic luminance information is spatially inconsistent with the color and texture of the target object, the observer's brain automatically combines these sensory signals in such a way as to correct the inconsistency across visual attributes. We conducted a psychophysical experiment to investigate the characteristics of the inconsistency correction and found that the correction was critically dependent on the retinal magnitude of the inconsistency. Another experiment showed that the perceived magnitude of image deformation produced by our techniques was underestimated. The results ruled out the possibility that the effect obtained by our technique stemmed simply from the physical change in an object's appearance by light projection. Finally, we discuss how our techniques can make the observers perceive a vivid and natural movement, deformation, or oscillation of a variety of static objects, including drawn pictures, printed photographs, sculptures with 3D shading, and objects with natural textures including human bodies.