Mechanisms of gloss perception

光泽知觉是材料知觉的一个重要方面。它还具有重要的功能相关性，例如在识别透明物体和检测光滑或潮湿的表面方面。计划中的研究项目主要涉及视网膜图像中的规律性，感知系统利用这些规律性来检测有光泽的物体并量化其材料特性。这些问题的澄清是困难的，因为光泽度与光源或物体从物体表面在环境中的反射密切相关。因此，视网膜图像不仅依赖于表面的材料属性，而且在相当大程度上还依赖于环境的属性。在这个项目中，我们将处理两个小主题，这两个主题直接跟随着正在进行的项目的前期工作和结果。第一个子项目的主要主题是如何将存在于不同表面点的局部光泽度线索整合到整体光泽度印象中。为此，我们一方面将研究物理光泽特性不均匀的材料，另一方面将使用由主要可区分特性的光源组成的复杂照明。这使得有可能系统地改变局部刺激属性并测量对整体光泽印象的相应影响。第二个子项目涉及当前项目阶段的一个重要结果，即在确定表面的光泽度时，视觉系统利用镜面反射强度取决于光线入射方向(菲涅耳效应)这一事实。在以往许多关于光泽感知的研究中，这种菲涅尔效应被忽略了。因此，在这类研究中获得的结果很可能具有有限的有效性。为了研究这个问题并量化对光泽度和光泽度稳定性的潜在影响，我们将重复一些在有和没有菲涅耳效应的情况下的关键研究。理论上的考虑和非正式的观察进一步表明，菲涅尔效应还包含可用于形状感知的信息，以及可用于材料识别的关于光源颜色的特定信息。因此，菲涅尔效应对形状和材料感知的潜在影响也将被研究。

The perception of gloss is an important aspect of material perception. It also has an important functional relevance, e.g. in the recognition of transparent objects and the detection of smooth or moist surfaces. The planned research project is primarily concerned with the regularities in the retinal image, which are used by the perception system to detect glossy objects and to quantify their material properties. The clarification of these questions is difficult, because gloss is closely related to the reflection of light sources or objects in the environment from the objects surface. For this reason, the retinal image is not only dependent on the material properties of the surface, but also to a considerable extent on the properties of the environment. In the project we will deal with two subtopics, which directly follow from preliminary work and results of the ongoing project. The main topic of the first subproject is how local glossiness cues, which are present at different surface points, e.g. isolated highlights, can be integrated into an overall gloss impression. To this end, we will, on the one hand, investigate materials which are inhomogeneous with regard to the physical gloss properties, and on the other hand, we will use complex illuminations, which consist of light sources with principally distinguishable properties. This makes it possible to systematically vary local stimulus properties and to measure the corresponding effect on the global gloss impression. A second subproject relates to an important result of the current project phase, namely that the visual system exploits the fact that the strength of the specular reflection depends on the direction of incidence of the light (Fresnel effect) when determining the glossiness of a surface. In many previous studies on gloss perception, such Fresnel effects have been neglected. It is therefore well possible that results obtained in such studies are of limited validity. In order to investigate this question and to quantify potential effects on gloss and gloss constancy, we will replicate some key studies on these topics with and without Fresnel effects. Theoretical considerations and informal observations further suggest that Fresnel effects also contain information that may be used in shape perception, and specific information about the color of the light sources that could be used in material recognition. Potential influences of Fresnel effects on shape and material perception will therefore also be investigated.