Surface Attitude Judgements in Real-World Scenes

Objective. Human observers can appreciate 3D properties such as surface attitude in 2D images. Here we evaluate methods for making surface attitude judgements for real-world scenes and the effect of context on such judgements. Methods: Real-world image patches from the SYNS dataset (Adams et al., 2016) were presented monocularly. In Experiment 1, we tested two response methods for judging 9° image patches: a gauge figure providing perspective cues and a 2D dial with separate slant and tilt indicators. In Experiment 2, we used the gauge figure method to compare judgments of patches with two different sizes: a 9° diameter circle presented full size and 64° by 36° patch presented at 37.5% of full size. The latter provided more contextual visual information. Results: Slant: Slant judgements from the gauge figure method correlated more strongly with the ground truth than the dial method and was reported to be the easier method to use. The larger patches (Exp 2) also produced a stronger correlation with ground truth than the smaller patches. Tilt: Some of our observers produced a significant correlation between tilt judgements and ground truth for the small image patches of Experiment 1. However, observers often mischaracterised many real-world tilt values as facing left or right, although cardinal facing surfaces were judged correctly. Preliminary data for Experiment 2 showed improved tilt judgements for the larger patches although the same mischaracterisation persisted. Conclusion: Both the gauge figure and dial methods can produce reasonable judgements of slant and tilt for real-world images, but the dial method is less reliable and more difficult to use. Tilt judgements for real-world images indicated a potential bias toward allocentric (gravity-centered) coordinates. While providing a wider field of view generally improves judgements, it does not eliminate this allocentric bias.