Evaluation of Perceptual Difference in Dynamic Projection Mapping with and without Movement of the Target Surface

Abstract

High-frame-rate visual feedback has been proven effective for projection mapping on quickly moving targets. However, the quantitative conditions of frame rates have not been elucidated. In particular, considering that the human dynamic visual acuity generally declines as the moving target velocity increases, it may be argued that the tracking accuracy required for projection mapping on moving targets can be lower than that required for fixed targets. To examine the above-mentioned conditions of frame rates, this study compares them based on two types of projection mapping systems having equivalent relative movements to each other: projection mapping from a fixed projector/camera system to a moving target and projection mapping from a moving projector/camera system to a fixed target. We examined the effects of the target movements by having stationary observers visually recognize and evaluate them. Using the weighted up-down method, we measured the frame time that provides a just noticeable difference (JND) to the projection mapping. We found that when the visual feedback is generated at a frame time of 2 ms, the frame time that provides a JND is 3.72 ms on average for fixed targets and 3.94 ms on average for moving targets: a 1%-level significant difference. Taking the individual differences and experimental errors into account, this is not a very large variation. This suggests that, in projection mapping to moving targets, we should realize a tracking accuracy as precise as that in projection mapping to fixed targets.