Surface tilt (the direction of slant): A neglected psychophysical variable
Surface tilt (the direction of slant): A neglected psychophysical variable
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表面倾斜（倾斜方向）：一个被忽视的心理物理变量
DOI：
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发表时间：
1983
期刊：
影响因子：
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通讯作者：
K. A. Stevens
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文献类型：
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作者：
K. A. Stevens
表面倾斜(视线与表面法线之间的夹角)是一个重要的心理物理变量。然而，倾斜角度仅捕获曲面方向的两个自由度中的一个，另一个是倾斜方向。在图像平面中测量的倾斜方向与从观察者到表面的距离梯度的方向一致，并且等价地，与如果投影到图像平面上表面法线将指向的方向一致。由于倾斜方向可以通过投影法线的倾斜度(在额面上的范围超过360度)来量化，因此这里指的是面倾斜度。(请注意，倾斜角度是垂直于图像平面测量的，而倾斜角度是在图像平面中测量的。)与倾斜角度作为心理物理变量的流行程度相比，对表面倾斜的关注似乎是不必要的。报道了一种测量表面表观倾斜度的实验。实验刺激是斜十字和平行四边形，这表明在3-D中有定向平面。可以通过在3-D中将针定向以使其看起来正常，将法线投影到图像平面上，并测量其方向(例如，相对于水平线)来探测平面的明显倾斜。然而，显示出仅在2-D中旋转叠加在显示器上的线段，直到它看起来垂直于所感知的表面，是更可取的。在这些实验中记录的表观表面倾斜度与假设3-D构型由等长线和垂直交点组成的预测结果非常一致。
Surface slant (the angle between the line of sight and the surface normal) is an important psychophysical variable. However, slant angle captures only one of the two degrees of freedom of surface orientation, the other being thedirection of slant. Slant direction, measured in the image plane, coincides with the direction of the gradient of distance from viewer to surface and, equivalently, with the direction the surface normal would point if projected onto the image plane. Since slant direction may be quantified by the tilt of the projected normal (which ranges over 360 deg in the frontal plane), it is referred to here assurface tilt. (Note that slant angle is measured perpendicular to the image plane, whereas tilt angle is measured in the image plane.) Compared with slant angle’s popularity as a psychophysical variable, the attention paid to surface tilt seems undeservedly scant. Experiments that demonstrate a technique for measuring apparent surface tilt are reported. The experimental stimuli were oblique crosses and parallelograms, which suggest oriented planes in 3-D. The apparent tilt of the plane might be probed by orienting a needle in 3-D so as to appear normal, projecting the normal onto the image plane, and measuring its direction (e.g., relative to the horizontal). It is shown to be preferable, however, to merely rotate a line segment in 2-D, superimposed on the display, until it appears normal to the perceived surface. The apparent surface tilt recorded in these experiments corresponded closely to that predicted by assuming the 3-D configurations consist of equal-length lines and perpendicular intersections.