Mechanisms of gloss perception

光泽的感知是材料感知的一个重要方面。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表面方面。计划中的研究项目主要涉及视网膜图像中的反射，感知系统使用这些反射来检测光滑物体并量化其材料特性。这些问题的澄清是困难的，因为光泽度与环境中的光源或物体从物体表面的反射密切相关。因此，视网膜图像不仅取决于表面的材料特性，而且在相当大的程度上取决于环境的特性。在这个项目中，我们将处理两个子主题，这两个子主题直接来自正在进行的项目的初步工作和结果。第一个子项目的主要主题是如何将局部光泽度提示（存在于不同的表面点，例如孤立的高光）整合到整体光泽印象中。为此，我们一方面将研究物理光泽特性不均匀的材料，另一方面将使用复杂的照明，这些照明由具有主要可区分特性的光源组成。这使得有可能系统地改变局部刺激特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成果，即视觉系统在确定表面光泽度时利用镜面反射的强度取决于光的入射方向（菲涅尔效应）这一事实。在以往的许多光泽感知研究中，这种菲涅耳效应被忽略了。因此，这些研究中获得的结果很可能有效性有限。为了研究这个问题并量化对光泽度和光泽度恒定性的潜在影响，我们将在有和没有菲涅尔效应的情况下复制这些主题的一些关键研究。理论考虑和非正式观察进一步表明，菲涅尔效应还包含可用于形状感知的信息，以及有关光源颜色的特定信息，可用于材料识别。因此，还将研究菲涅耳效应对形状和材料感知的潜在影响。

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.