Mamassian P, Landy M S
Department of Psychology, New York University, NY 10003, USA.
Vision Res. 1998 Sep;38(18):2817-32. doi: 10.1016/s0042-6989(97)00438-0.
Line drawings produced by contours traced on a surface can produce a vivid impression of the surface shape. The stability of this perception is notable considering that the information provided by the surface contours is quite ambiguous. We have studied the stability of line drawing perception from psychophysical and computational standpoints. For a given family of simple line drawings, human observers could perceive the drawings as depicting either an elliptic (egg-shaped) or hyperbolic (saddle-shaped) smooth surface patch. Rotation of the image along the line of sight and change in aspect ratio of the line drawing could bias the observer toward either interpretation. The results were modeled by a simple Bayesian observer that computes the probability to choose either interpretation given the information in the image and prior preferences. The model's decision rule is noncommitting: for a given input image its responses are still probabilistic, reflecting variability in the modeled observers' judgements. A good fit to the data was obtained when three observer assumptions were introduced: a preference for convex surfaces, a preference for surface contours aligned with the principal lines of curvature, and a preference for a surface orientation consistent with an object viewed from above. We discuss how these assumptions might reflect regularities of the visual world.
通过在曲面上追踪轮廓生成的线条图能够生动地展现曲面形状。考虑到曲面轮廓所提供的信息相当模糊，这种感知的稳定性便显得尤为突出。我们从心理物理学和计算的角度研究了线条图感知的稳定性。对于给定的一组简单线条图，人类观察者能够将这些图视为描绘了一个椭圆形（蛋形）或双曲线形（鞍形）的光滑曲面块。图像沿线的视线旋转以及线条图长宽比的变化可能会使观察者偏向于其中一种解释。结果由一个简单的贝叶斯观察者模型进行模拟，该模型根据图像中的信息和先验偏好计算选择两种解释的概率。该模型的决策规则并不明确：对于给定的输入图像，其响应仍然是概率性的，反映了模拟观察者判断中的变异性。当引入三个观察者假设时，该模型与数据拟合良好：对凸面的偏好、对与主曲率线对齐的曲面轮廓的偏好以及对与从上方观察物体一致的曲面方向的偏好。我们讨论了这些假设如何可能反映视觉世界的规律。
