Glossary
Terms used in accessibility research and practice. Each entry has a definition, common aliases, and category tags.
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- Ray Casting(also: Raycasting)
- An interaction technique in 3-D environments where an invisible ray is projected from a point (such as a user's finger position or controller) into the virtual scene to determine which object the ray intersects first. In VR accessibility, ray casting translates 2-D touch input…
- Redundant Input(also: Redundant Input Channels, Multimodal Redundancy)
- A design approach in which a user interface accepts the same command through more than one input channel — for example, voice and gesture, keyboard and pointer, or speech and switch — so that users can choose whichever modality suits their current abilities, context, or…
- Relevance Threshold(also: Filtering Threshold, Display Threshold)
- A user-adjustable cutoff value that determines which content elements are displayed or hidden based on their relevance scores. Elements scoring above the threshold are shown; those below are de-emphasized or removed. Relevance thresholds provide users with agency over how…
- Row-Column Scanning(also: RCS, Grid Scanning, Two-Switch Scanning)
- The most widely used single-switch selection method for augmentative and alternative communication (AAC) devices and on-screen keyboards. Options are arranged in a two-dimensional grid, and the interface sequentially highlights each row. When the user clicks their switch, the…
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