Perceived roughness of glossy objects: The influence of Fresnel effects and correlated image statistics

Influence of Fresnel effects on the glossiness and perceived depth of depth-scaled glossy objects

Fresnel effects, that is, shape-dependent changes in the strength of specular reflection from glossy objects, can lead to large changes in reflection strength when objects are scaled along the viewing axis. In an experiment, we scaled sphere-like bumpy objects with fixed material parameters in the depth direction and then measured with and without Fresnel effects how this influences the gloss impression, gloss constancy, and perceived depth. The results show that Fresnel effects in this case lead to a strong increase in gloss with depth, indicating lower gloss constancy than without them, but that they improve depth perception. In addition, we used inverse rendering to investigate the extent to which Fresnel effects in a rendered image limit the possible object shapes in the underlying scene. We found that, for a static monocular view of an unknown object, Fresnel effects by themselves provide only a weak constraint on the overall shape of the object.

Glossy Appearance Editing for Heterogeneous Material Objects

Abstract With the proliferation of smartphones and social networking services, the opportunities for individuals to take photographs have increased exponentially. In a previous study, the perceived gloss of an object was reduced by its representing as a digital image and compared with a real object. It is also known that image editing, such as lossy image compression, can reduce the glossiness of an image. Therefore, the glossiness of real objects may be easily changed in digital images; thus, a method for appropriately editing the gloss in digital images is required for post-processing. In this study, we propose a gloss appearance editing method for various material objects in a single digital image. The proposed method consists of three steps: color space conversion, gloss detection, and gloss editing. The relationship between the proposed method and the respective reflection models of inhomogeneous objects, metallic objects, and translucent objects was analyzed. Consequently, we determined that the gloss editing of the proposed method is equivalent to editing the specular reflection component of an inhomogeneous object, the grazing reflection component of a metallic object, and the specular reflection component of a translucent object. We applied the proposed method to test images including objects of various materials and confirmed its effectiveness through a subjective evaluation by visual inspection and an objective evaluation using image statistics.