Clone Attack! Perception of Crowd Variety
Rachel McDonnell
MicheĢal Larkin
Simon Dobbyn
Steven Collins
Carol O’Sullivan
∗Graphics, Vision and Visualization Group, Trinity College Dublin.
Figure 1: Example of a crowd used in the Appearance Variation Experiment with the maximum number of clones.
Abstract
When simulating large crowds, it is inevitable that the models and
motions of many virtual characters will be cloned. However, the
perceptual impact of this trade-off has never been studied. In this
paper, we consider the ways in which an impression of variety
can be created and the perceptual consequences of certain design
choices. In a series of experiments designed to test people’s per-
ception of variety in crowds, we found that clones of appearance
are far easier to detect than motion clones. Furthermore, we estab-
lished that cloned models can be masked by color variation, random
orientation, and motion. Conversely, the perception of cloned mo-
tions remains unaffected by the model on which they are displayed.
Other factors that influence the ability to detect clones were exam-
ined, such as proximity, model type and characteristic motion. Our
results provide novel insights and useful thresholds that will assist
in creating more realistic, heterogeneous crowds.
CR Categories:
I.3.7 [Computer Graphics]: Three-Dimensional
Graphics and Realism—[Animation]
Keywords: perception, variety, crowds, animation
1
Introduction
Realistic virtual environments depicting thousands of virtual hu-
mans can be challenging to create due to a number of limiting fac-
tors. For data-driven crowd systems, assets such as skinned human
models and motion captured character animations can be expensive
to purchase or commission, while system resources are a further
constraint. Therefore, a fixed number of template characters are
usually deployed to generate large crowds using instancing, thus
∗http://gv2.cs.tcd.ie/
producing Appearance Clones (AC ) that can often be easily no-
ticed. Character motions also consume memory resources, which