3D Environments Require 3D Visualisations

1Problem

We assess 3D spatial knowledge with a 2D medium. Pen-and-paper sketch maps of vertically-complex environments make it difficult to draw and assess vertical understanding.

A 2D pen-and-paper sketch map from our dataset, showing the difficulty of representing vertical structure on flat paper.

A 2D pen-and-paper sketch map from our dataset (Exp 1, participant id24). The vertically layered building has to be flattened onto the page, so up–down relations are hard to draw and hard to assess.

2Method

Two VR experiments. Each participant produced a 2D pen-and-paper and a 3D Gravity Sketch map of the same environment.

Experiment 1 environment: a three-storey building with the middle floor rotated 90 degrees, viewed in cutaway.

Exp 1 · Vertically layered building

n: 27
Levels: 3 (middle rotated 90°)
Landmarks: 6 (3 in, 3 out)
Locomotion: Joystick (free)

▶ Video demonstration of the experimental procedure

Experiment 2 environment: an urban scene of six buildings with landmarks placed at three different heights.

Exp 2 · Vertically volumetric urban scene

n: 37
Buildings: 6
Landmark heights: 3 levels
Locomotion: Drone fly-through

▶ Video demonstration of the experimental procedure

Each sketch was coded for occurrence and correctness of qualitative spatial relations along X, Y, Z axes separately. Bayesian Bernoulli mixed-effects models with random effects for participant and relation.

3Results

2D sketch maps act as a bottleneck: people store vertical spatial knowledge that the 2D medium hides but a 3D medium reveals.

H1 · supported

When drawing on paper, people show a bias toward the horizontal plane: they leave out vertical (up–down) relations far more often than horizontal ones.

Exp 1 · building

2.0× lower odds

OR 0.49, 95% CI [0.22, 1.10] · posterior 93%, moderate.

Exp 2 · urban

35× lower odds

OR 0.03, 95% CI [0.02, 0.05] · posterior ~100%, strong.

H2 · not supported

When a vertical relation is drawn in both formats, the 3D sketch is no more accurate than the 2D one. 3D doesn't make relations more correct — just more likely to appear.

Exp 1 · building

no difference

log-OR −0.32, 95% CI [−1.17, 0.52] · ~3× more likely under null.

Exp 2 · urban

no difference

log-OR −0.31, 95% CI [−0.76, 0.12] · ~7× more likely under null.

H3 · supported

When a relation is missing from someone's 2D sketch but appears on their 3D sketch, it's mostly correct — the spatial knowledge was there; the 2D medium was hiding it.

Exp 1 · building

91% correct

OR vs chance 10.5, 95% CI [6.5, 17.5] · posterior ~100%.

Exp 2 · urban

67% correct

OR vs chance 1.88, 95% CI [1.47, 2.41] · posterior ~100%.

4Sketch maps

Every participant’s 2D and 3D sketch, side by side. Click a card.