Zhang Fan, de Ridder Huib, Barla Pascal, Pont Sylvia
Perceptual Intelligence Lab, Faculty of Industrial Design Engineering, Delft University of Technology, Delft, The Netherlands.
INRIA, University of Bordeaux, Talence, France.
J Vis. 2019 Apr 1;19(4):11. doi: 10.1167/19.4.11.
Photographers and lighting designers set up lighting environments that best depict objects and human figures to convey key aspects of the visual appearance of various materials, following rules drawn from experience. Understanding which lighting environment is best adapted to convey which key aspects of materials is an important question in the field of human vision. The endless range of natural materials and lighting environments poses a major problem in this respect. Here we present a systematic approach to make this problem tractable for lighting-material interactions, using optics-based models composed of canonical lighting and material modes. In two psychophysical experiments, different groups of inexperienced observers judged the material qualities of the objects depicted in the stimulus images. In the first experiment, we took photographs of real objects as stimuli under canonical lightings. In a second experiment, we selected three generic natural lighting environments on the basis of their predicted lighting effects and made computer renderings of the objects. The selected natural lighting environments have characteristics similar to the canonical lightings, as computed using a spherical harmonic analysis. Results from the two experiments correlate strongly, showing (a) how canonical material and lighting modes associate with perceived material qualities; and (b) which lighting is best adapted to evoke perceived material qualities, such as softness, smoothness, and glossiness. Our results demonstrate that a system of canonical modes spanning the natural range of lighting and materials provides a good basis to study lighting-material interactions in their full natural ecology.
摄影师和灯光设计师根据经验总结的规则，营造出最能展现物体和人物形象的灯光环境，以传达各种材料视觉外观的关键特征。了解哪种灯光环境最适合传达材料的哪些关键特征，是人类视觉领域的一个重要问题。在这方面，自然材料和灯光环境的种类繁多构成了一个重大问题。在此，我们提出一种系统方法，利用由典型灯光和材料模式组成的基于光学的模型，使这个问题在灯光与材料相互作用方面变得易于处理。在两项心理物理学实验中，不同组的无经验观察者对刺激图像中描绘的物体的材料特性进行了判断。在第一个实验中，我们在典型灯光下拍摄真实物体作为刺激物。在第二个实验中，我们根据预测的灯光效果选择了三种通用的自然灯光环境，并对物体进行了计算机渲染。所选的自然灯光环境具有与典型灯光相似的特征，这是通过球谐分析计算得出的。两项实验的结果高度相关，表明（a）典型材料和灯光模式如何与感知到的材料特性相关联；以及（b）哪种灯光最适合唤起诸如柔软度、光滑度和光泽度等感知到的材料特性。我们的结果表明，一个跨越灯光和材料自然范围的典型模式系统为在其自然生态环境中全面研究灯光与材料的相互作用提供了良好的基础。
