When an object casts a shadow on a background surface, both the offset of the shadow and the blur of its penumbra are potential cues to the distance between the object and the background. However, the shadow offset and blur are also affected by the direction and angular extent of the light source and these are often unknown. This means that the observer must make some assumptions about the illumination, the expected distribution of depth, or the relation between offset and depth in order to use shadows to make distance judgments. Here, we measure human judgments of perceived depth over a range of shadow offsets, blurs, and lighting directions to gain insight into this internal model. We find that distance judgments are relatively unaffected by blur or light direction, whereas the shadow offset has a strong and linear effect. The data are consistent with two models, a generic shadow-to-depth model and a Bayesian model.

中文翻译：

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从阴影偏移缩放深度。

当物体在背景表面投射阴影时，阴影的偏移和半影的模糊都是物体与背景之间距离的潜在线索。然而，阴影偏移和模糊也受到光源的方向和角度范围的影响，这些通常是未知的。这意味着观察者必须对光照、预期的深度分布或偏移与深度之间的关系做出一些假设，以便使用阴影来进行距离判断。在这里，我们在一系列阴影偏移、模糊和照明方向上测量人类对感知深度的判断，以深入了解这个内部模型。我们发现距离判断相对不受模糊或光线方向的影响，而阴影偏移具有强烈的线性影响。