Tactile Vega-Lite: Rapidly Prototyping Tactile Charts with Smart Defaults

TL;DR

Tactile Vega-Lite (TVL) extends the Vega-Lite grammar with tactile-specific abstractions, including texture encodings, braille integration, navigational aids, and layout controls, paired with smart defaults aligned to tactile design guidelines. The system enables non-experts to rapidly prototype guideline-conformant tactile charts while preserving expert customization through override capabilities; a prototype editor renders SVG outputs suitable for embossing or swell-form production. A user study with 12 tactile graphics designers demonstrates that TVL accelerates iteration and enhances consistency via predefined textures and line styles, while highlighting the ongoing need for customization and production tooling. The work advances tactile-first data representation design and motivates future multimodal accessibility research, with implications for tooling that bridges design, production, and reader experience.

Abstract

Tactile charts are essential for conveying data to blind and low vision (BLV) readers but are difficult for designers to construct. Non-expert designers face barriers to entry due to complex guidelines, while experts struggle with fragmented and time-consuming workflows that involve extensive customization. Inspired by formative interviews with expert tactile graphics designers, we created Tactile Vega-Lite (TVL): an extension of Vega-Lite that offers tactile-specific abstractions and synthesizes existing guidelines into a series of smart defaults. Predefined stylistic choices enable non-experts to produce guideline-compliant tactile charts quickly. Expert users can override defaults to tailor customizations for their intended audience. In a user study with 12 tactile graphics creators, we show that Tactile Vega-Lite enhances flexibility and consistency by automating tasks like adjusting spacing and translating braille while accelerating iterations through pre-defined textures and line styles. Through expert critique, we also learn more about tactile chart design best practices and design decisions.

Figures (10)

• Figure 1: Comparison of visual and tactile charts representing fertility rate trends for China and Australia from 1955 to 2005. This comparison shows design considerations necessary when transforming visual data into tactile formats, such as converting text to braille, adjusting scaling and spacing of chart elements, re-arranging the legend, and substituting visual encodings with tactile encodings.
• Figure 2: Example walkthrough of an expert designer's tactile chart creation process. 1) Tracing a visual reference. 2) Creating tactile encodings. 3) Creating a legend. 4) Adjusting spacing. 5) Scaling the axes to avoid overlaps.
• Figure 3: Braille representations of the word 'Australia' in Grade 1 (left) and Grade 2 (right).
• Figure 4: Educators often use a combination of specialized software, embossing techniques, and hands-on materials to create tactile graphics that convey visual information in accessible formats for blind and low-vision students.
• Figure 5: Tactile chart creators can use the TVL code editor to customize key properties such as axis labels, tick marks, sorting, and texture encodings. The rendered outputs on the right showcase the parallel visual and tactile representations. Highlighted code snippets in yellow show properties that were added in TVL.