The diffuseness of light and its angle of incidence influence the way we perceive material properties like roughness and shininess, but whether it influences our ability to discriminate between differently textured materials is unclear. Therefore we examined the effect of diffuseness and direction of light on the perceived texture visibility of images of different materials. Images were made under strongly collimated or strongly diffuse lighting and superimposed to obtain mixed images with varying diffuseness levels. Participants rated texture visibility pairs of images using a 2-alternative forced choice task (AFC). We found that overall the perceived texture visibility was best for the most diffuse light source and worst for intermediate diffuseness levels. Texture visibility improved with angle of incidence for collimated lighting. The effect of the diffuseness level of the illuminant was strongly dependent the material. Our results confirm that the diffuseness of light is an important factor for discriminating textures of real materials.
How do different object properties combine for the purposes of object identification? We developed a paradigm that allows us measure the degree to which human observers rely on one object property (e.g., color) vs. another (e.g., material) when they make forced-choice similarity judgments. On each trial of our experiment, observers viewed a target object paired with two test objects: a material match, that differed from the target only in color (along a green-blue axis) and a color match, that differed from the target only in material (along a glossy-matte axis). Across trials, the target was paired with different combinations of material-match and color-match tests and observers selected the test that appeared more similar to the target. To analyze observer responses, we developed a model (a two-dimensional generalization of the maximum-likelihood difference scaling method) that allows us to recover (1) the color-material weight, reflecting the relative importance of color vs. material in object identification and (2) the underlying positions of the material-match and color-match tests in a perceptual color-material space. Our results reveal large individual differences in the relative weighting of color vs. material.
Particular motions are important to play sports with high performance. The particular motions are mastered by learning motions, and visual information is considered to be effective for understanding and learning motions. In recent years, HMD with VR has been introduced as a new tool for learning motions with visual information. An advantage of the HMD-based motion learning method is that it enables learners to switch their observation view. Here, this research investigates basic view characteristics of observing and reproducing particular dynamic motions, which would be necessary to develop some methods for switching observation view properly. An experiment was conducted in order to study the basic view characteristics. As for the observation view factor, we prepared two factor levels, one was the front mirror view, and the other the rear camera view. In the experiment, a subject recognized and reproduced some reference dynamic motions on real time with each of the two views. The experimental results revealed that the reproduction performance with the rear camera view was significantly better than that with the front mirror view in the case of the depth-directional motions, compared with the other case of the depth-uncorrelated motions. It should be noted that the difference in the motion reproduction may become crucial for learners in particular as the motion velocity increases. It is supposed that the observation with the front mirror view requires some mental transformation operation when the learners reproduce motions. In selecting the observation view, it is required to minimize the mental transformation operation. The requirement is expected to be satisfied with the rear camera view, provided that occlusions are not crucial for learners to observe reference motions.