How our brain designs 3D shapes from shades!

How our brain designs 3D shapes from shades!

On July 11, 2025, researchers from the Justus Liebig University Giessen in cooperation with Yale University published a groundbreaking article in the journal PNAS that could significantly influence the perception of 3D shapes. The study examines how people perceive shades and their influence on the construction of three-dimensional images in the brain.

Previously, it was assumed that the human brain interpreted shades in a similar way to machines, by backwards engineering shape and lighting. This study challenges this concept. The researchers show that the brain uses so-called “edge detectors” to identify lines and sketch 3D shapes. Shading patterns that appear in the brain outline blurry lines that follow the 3D curves of objects.

New insights into shading perception

A key finding of the research is that physically correct shading is not necessary to perceive 3D shapes. Even “strange” shades that break physical rules produce similar perceptions to correct shades. This applies to shaded objects made of different materials, from matte to shiny chrome. The results suggest that edge detection plays a larger role in visual perception than previously thought.

The research team is already planning further studies to investigate how learned relationships between line patterns and 3D objects influence human perception. This could have far-reaching implications for our understanding of perceptual psychology and the way we process visual information.

Basics of perception psychology

Perceptual psychology, which deals with the subjective component of perception, plays a crucial role in this context. She examines the differences between objectively measurable physical properties and the subjective perception of stimuli, which often cannot be fully explained by objective sensory physiological aspects.

For example, a deciduous tree is not perceived as a collection of individual leaves, but as an entire object. This subjective perception can be illustrated by optical illusions that highlight the discrepancy between what we see and what actually is. There are several stages involved in this process of perception: sensing, organizing and classifying, all of which are necessary to understand and interpret sensory impressions.

Furthermore, it becomes clear that experience influences perception, as already described by Hermann von Helmholtz. James J. Gibson's ecological theory of perception also suggests that perception depends on the analysis of environmental information and the specific options for action that living beings have.

The findings of this study could not only be important for basic research on perception, but also have applications in various fields, from visual art to robotics. Further information is available, among other things, in the master’s program “Mind, Brain and Behavior” at JLU.