How users differentiate imposters from real models : Investigating a Level Of Detail-technique for crowd simulators

Sammanfattning: Crowd Simulators are used to see how large virtual crowds behave. They are mostly used to simulate crowd behaviors. One of the constraints with crowd simulators is the level of detail that should be used to still have a realistic simulation. This thesis explores the idea of using imposters as a method of lowering the level of detail. Imposters are 3D-models in a scene that are only rendered as two-dimensional objects when they are far enough from the camera. The general problem statement of this thesis is to see how well people can differentiate between 3D-models and imposters. This is tested with the underlying problem how presentation affects how one interpret imposters. Presentation is tested in regards to the distance the camera have from the imposter and from what angle you look at imposters from. Using Unity 3D, an implementation of imposters was created that can capture an imposter, render an imposter and make the imposter move in different camera angles. A user study was conducted to test how well this implementation works in regard to presentation. The study consisted of several movie clips showing an imposter and its original model walking down a road. Users had to push a button when they saw through the imposter. From the user study, it was shown that distance from the camera do affect how one sees an imposter. Almost all of the other factors does not have a significant difference from each other. Users attest to that they were specifically looking for any visual artifacts and aliasing in the imposter to find any faults in them. It would have been interesting to try this implementation in a real crowd simulator. It would help to enable using other camera angles as factors to have more extreme cases to compare to. The recommendation is to try to not use imposters outside of crowd simulators, as it is too easy to see a difference between imposters and their models if the imposter is too close.