RSE Day 2025 · The development of OCTA: A Python toolbox and point-and-click application for visual stimulus generation in psychology

Eline Van Geert
Research Software Engineering Day 2025 · December 4, 2025 · Leuven, Belgium

The Order & Complexity Toolbox for Aesthetics (OCTA) is a recently developed, freely available open-source Python toolbox and point-and-click online Shiny application to create visual stimuli containing multiple elements, with tools to manipulate regularity (order) and variety (complexity) along multiple element features (e.g., position, shape, size, color, orientation) in a controlled manner (Van Geert, Bossens, & Wagemans, 2023; https://elinevg.github.io/OCTA/). Elements can include geometric shapes, but also images or custom-defined vector-based shapes. The standard vector-based output is ideal for online use and the creation of dynamic interfaces and stimuli, but raster-based output is possible too. Furthermore, some element or stimulus characteristics can be easily animated over time. Although the toolbox is mainly meant to provide perception and aesthetics researchers with a free and easy way to create reproducible and parametrically manipulated stimulus sets, it can also be used by the general public to easily create interesting visual displays. Furthermore, outcomes from research using OCTA stimuli can also be visualized using interactive online applications (e.g., https://elinevg.shinyapps.io/OCTAratings_explore/), making research data available for exploration by a broader audience in an easy and interactive way. In this presentation, we will introduce the open-source toolbox, discuss why this open-source toolbox was created and detail decisions taken in the development process.