Enhancing Size Perception with True-Size Viewing CAD plug-in and Cloud-enabled AR APP

Abstract

Introduction: Compared with sketching or viewing the drawing on paper at the scale of 1:1, it is difficult to have an intuitive understanding of the part size when designing and viewing models in CAD software since the displayed size usually differs from its true size[2]. The reason for this is the inaccurate size perceiving process. Size perception refers to the complex cognitive behavior of interpreting the spatial geometry magnitude of objects[5][10]. A familiar object's perceived size remains identical regardless of the changing distance[8]. This phenomenon is known as size constancy[11], and it helps humans estimate the size of unfamiliar objects. However, the part in the CAD is usually of low familiarity and presented without any familiar object, so the size perception is based on the perceived target distance and the visual angle. When observing a virtual object shown on the monitor, the convergence of two eyeballs focusing on the same object plays the most important role among all cues[3][9]. 3D CAD software uses the 2D image of a virtual camera targeting the model located at a virtual distance to display 3D models. The viewer perceives the displayed size instead of the true size, while the perceived target distance is the distance between the viewer's eyes and the monitor. Even when the virtual model is placed in a virtual environment identical to the real scene, it is also perceived to be smaller than the real object, although the retinal size is the same[12]. The CAD Window will show all the Camera Range, and the ratio of CAD Window Size to the Displayed Size equals the one of Max Camera Range to True Size. Fig. 1 is listed below to illustrate the display method in the 3D CAD more clearly.