Impact of Background Type and Text Orientation Angle on Glance-Based 3D Text Legibility for Mixed-Reality Applications

Textual information in augmented and mixed-reality (AR/MR) is often presented as two-dimensional, front-facing content. Spatially oriented 3D text provides an alternative that may allow textual information to be integrated more naturally into the surrounding environment and potentially reduce scene occlusion. However, introducing spatial orientation also raises questions about how text orientation angle and complex visual backgrounds affect text legibility. This study examined the effects of background type and text orientation angle using a glance-based methodology for assessing 3D text legibility in a controlled screen-based simulation relevant to handheld MR. Eighteen participants completed all experimental conditions (270 trials per participant) in which white 3D text was displayed for 659 ms at 15°, 30°, and 45° over three types of complex backgrounds, each represented by three images. Objective performance was assessed using accuracy and total error and complemented by Raw NASA-TLX and subjective ratings. Text orientation angle produced the strongest and most consistent effect: performance was the lowest at 15° and substantially improved at 30° and 45°, while subjective workload was the highest at 15°. Background-type effects were smaller and varied across angles and outcome measures, with no single category consistently producing the highest or lowest legibility. Considerable variability was also observed among individual background images and specific text stimuli. The findings indicate that spatial orientation is a major determinant of glance-based 3D text legibility, while the impact of background type was less consistent.