Consistency of a Tactile Pattern Set
Denise Prescher, Jens Bornschein, Gerhard Weber · 2017 · ACM Transactions on Accessible Computing · doi:10.1145/3053723
Summary
This paper addresses a fundamental challenge in tactile graphics production: how to create fill patterns that remain recognizable and distinguishable across different production media with varying resolutions. The three media studied were microcapsule (swell) paper (>20 dpi), high-resolution Braille embossers (~20 dpi), and pin-matrix devices like the BrailleDis 7200 (~10 dpi). The researchers used a user-centered design approach, starting with 45 candidate patterns derived from existing guidelines (including BANA) and prior research. Five tactile graphics experts narrowed this to 24 patterns through preselection. The main study involved 9 blind participants (ages 21-51, mix of early and late blind) who explored patterns on all three media, rating both recognizability within each medium and similarity across media. A follow-up contrast rating study with 10 participants (8 blindfolded sighted, 2 blind) confirmed distinguishability of the final set. The entire methodology prioritized practical usability over theoretical completeness, with the explicit goal of creating a pattern palette that real users could reliably work with.
Key findings
The final pattern set consists of 9 patterns that work across all three production media: solid fill, vertical lines, horizontal lines, dashed double lines, grid, dots, stair pattern, and two diagonal line variants (wide and close spacing). Several patterns were rejected due to confusion—circles were too similar to grids on low-resolution displays, vertical strokes confused with horizontal lines, and filled squares mistaken for dotted patterns. The research confirmed that for good pattern contrast, patterns must differ in at least two tactile features: shape or size of elements, spacing or frequency, and direction. Participants tolerated variations in line width and spacing across media but were less tolerant of size variations. An important practical finding was that 12 patterns can be reliably remembered during exploration, while 36 patterns overwhelmed users. The study also found that simple line and dot patterns consistently performed best, validating earlier research by Schiff on tactile contrast principles.
Relevance
This work provides an immediately usable resource for anyone creating tactile graphics. The complete SVG code for all 9 patterns is published, with media-specific versions that can be embedded directly in graphics production workflows. The patterns are already integrated into the Tangram workstation, a LibreOffice extension for collaborative tactile graphics creation. For practitioners, the key takeaway is the importance of cross-media consistency—when educational materials may be produced in multiple formats, using this validated pattern set ensures blind users encounter the same tactile vocabulary regardless of production method. The research also offers practical guidance: limit graphics to 7-12 different patterns, ensure patterns differ in at least two tactile dimensions, and prefer simple geometric patterns over complex figural ones.
Tags: tactile graphics · blindness · non-visual access · fill patterns · cross-media consistency · user-centered design
Standards referenced: BANA Guidelines for Tactile Graphics