# Geometric illusions

Geometric illusions research focuses on how our visual system misperceives size, length, angle, and other spatial properties of objects. Unlike lightness perception where the challenge is understanding how we see surface properties, geometric illusions reveal how spatial context systematically distorts our perception of basic geometric features. This area has attracted research interest partly because these illusions are often striking and counterintuitive - identical objects can appear dramatically different in size depending on their context.

## Why geometric illusions matter

These illusions aren't just curious demonstrations; they reveal fundamental principles about how our visual system processes spatial information. Each classic illusion highlights different aspects of spatial processing - from how surrounding context influences size perception to how our visual system integrates local and global information. The fact that these effects are robust and measurable makes them valuable tools for understanding visual processing mechanisms.

## Stimupy's approach

We've collected the major geometric illusions that have shaped our understanding of spatial vision. Here's what you'll find:

**Size illusions**: The classic Delboeuf illusion (`delboeufs`) where identical circles appear different sizes depending on surrounding rings, and various context effects that show how surrounding elements distort size perception.

**Length distortions**: The famous Müller-Lyer illusion (`mueller_lyers`) where identical line segments appear different lengths depending on the direction of arrowheads, and the Ponzo illusion (`ponzos`) where converging lines create perspective-like size distortions.

**3D perspective effects**: Including cube illusions (`cubes`) that use wireframe designs to create depth ambiguity and size distortions, and various stimuli that exploit our visual system's automatic perspective processing.

**Complex spatial patterns**: Things like Mondrian patterns (`mondrians`) for studying spatial segmentation, and other geometric arrangements that reveal how our visual system organizes and processes complex spatial layouts.


## Getting started

If you're studying spatial vision, testing computational models of size perception, or exploring how context affects geometric judgments, these tools give you precise control over the classic illusions. Each comes with flexible parameterization so you can explore the conditions that make these effects stronger or weaker.