Previous research investigated the perceptual dimensionality of achromatic reflection of opaque surfaces, by using either simple analytic models of reflection or measured reflection properties of a limited sample of materials. Here, we aim to extend this work to a broader range of simulated materials. In a first experiment, we used sparse multidimensional scaling techniques to represent a set of rendered stimuli in a perceptual space that is consistent with participants’ similarity judgments. Participants were presented with one reference object and four comparisons, rendered with different material properties. They were asked to rank the comparisons according to their similarity to the reference, resulting in an efficient collection of a large number of similarity judgments. To interpret the space individuated by multidimensional scaling, we ran a second experiment in which observers were asked to rate our experimental stimuli according to a list of 30 adjectives referring to their surface reflectance properties. Our results suggest that perception of achromatic reflection is based on at least three dimensions, which we labelled “Lightness,” “Gloss,” and “Metallicity,” in accordance with the rating results. These dimensions are characterized by a relatively simple relationship with the parameters of the physically based rendering model used to generate our stimuli, indicating that they correspond to different physical properties of the rendered materials. Specifically, “Lightness” relates to diffuse reflections, “Gloss” to the presence of high contrast sharp specular highlights, and “Metallicity” to spread out specular reflections.

中文翻译：

---

镜面反射和漫反射的三个感知维度

先前的研究通过使用简单的反射分析模型或测量有限材料样本的反射特性，研究了不透明表面消色差反射的感知维度。在这里，我们的目标是将这项工作扩展到更广泛的模拟材料。在第一个实验中，我们使用稀疏多维缩放技术来表示与参与者的相似性判断一致的感知空间中的一组渲染刺激。向参与者展示了一个参考对象和四个比较，用不同的材料属性渲染。他们被要求根据与参考的相似性对比较进行排名，从而有效地收集了大量的相似性判断。为了解释由多维尺度划分的空间，我们进行了第二个实验，要求观察者根据 30 个形容词的表面反射特性对我们的实验刺激进行评分。我们的结果表明，消色差反射的感知至少基于三个维度，我们根据评级结果将其标记为“亮度”、“光泽度”和“金属度”。这些维度的特点是与用于生成我们的刺激的基于物理的渲染模型的参数的关系相对简单，表明它们对应于渲染材料的不同物理特性。具体来说，“亮度”与漫反射有关，“光泽”与高对比度的尖锐镜面高光有关，“金属性”与分散镜面反射有关。