The inherent freedom of exploration in virtual reality poses a challenge for directing user attention toward relevant points or objects of interest, which are potentially located outside the user's field of view or are temporarily obscured. Accordingly, guidance must sustain users' perceptual focus while preserving the sense of presence. This paper presents RippleVision, a subtle gaze guidance technique using wave-like ripples that modulate brightness with inverted polarity between the eyes and appear only within a cone from the point of interest to the gaze location. A calibration study defined detectability and acceptability thresholds for the cues, followed by a comparative user study against four state-of-the-art techniques. Results show RippleVision achieves similar search times to clearly visible techniques while significantly reducing visual dominance. Moreover, its effectiveness scales with cue visibility, improving search performance with minimal impact on perceived visual obstruction and presence.

Foveated rendering adapts the image synthesis process to the user’s gaze. By exploiting the human visual system’s limitations, in particular in terms of reduced acuity in peripheral vision, it strives to deliver high-quality visual experiences at very reduced computational, storage, and transmission costs. Despite the very substantial progress made in the past decades, the solution landscape is still fragmented, and several research problems remain open. In this work, we present an up-to-date integrative view of the domain from the point of view of the rendering methods employed, discussing general characteristics, commonalities, differences, advantages, and limitations. We cover, in particular, techniques based on adaptive resolution, geometric simplification, shading simplification, chromatic degradation, as well spatio-temporal deterioration. Next, we review the main areas where foveated rendering is already in use today. We finally point out relevant research issues and analyze research trends.