Choosing rendering parameters for effective communication of 3D shape

We conducted a series of perceptual experiments to assess the contributions of rendering parameters to the perception of the shape of three-dimensional objects. For the experiments, observers viewed graphically rendered displays consisting of pairs of rotating objects and judged whether their shapes were identical. For some pairs they were, while for other pairs they differed by varying amounts. We determined the accuracy of shape perception from these discrimination judgments. We provide background information for the operational definition of shape used throughout the experiments, as well as for the rendering factors under experimental investigation: occluding contour, smooth shading, and specular highlights. Following that, we describe a series of experiments. Experiment 1 demonstrated the effectiveness of our new technique for the exploration of perceptual issues related to graphic interfaces. An additional four experiments produced results concerning the effects of rendering parameters on the communication of 3D shape. Experiments 2 and 3 investigated the contributions of basic rendering conditions such as the presence of occluding contours and smooth surface shading. In Experiments 4 and 5, the manipulation of specular highlighting revealed that accurate shape discrimination judgments were possible either with or without the specular component. These results lay a foundation for reasoned manipulation of interface properties when accurate communication of 3D shape is a primary goal of the display.