Rendering massive real-time crowds

This thesis presents how to visualize a large crowd of virtual human characters in real time on a standard issue personal computer. The virtual humans are distributed into rendering fidelities such that the humans closer to the viewer are detailed and expressive while the further away they are, the less detailed they become. Fidelity partitioning starts with fully dynamic and geometric humans, meaning they can perform a full suit of animations even computed on-demand. Dynamic geometry is followed by static geometry such that a constrained set of animations can be achieved while the last and farthest detail level from the viewer is image-based and static. Various rendering accelerations applicable to each fidelity are used and compared, such as caching schemes, levels-of-detail, shaders and state sorting. Memory usage and artistic workload is reduced using template humans that are instantiated with individual varieties in animation, clothing, facial appearance and color combinations. An innovative constraining method for randomized colors is presented. With the opportunity of rendering large crowds, emerges the need for novel interaction methods such as the CrowdBrush, an intuitive spraycan interface for crowds. In the area of virtual therapy, individual human picking is presented using the GazeMap. Several other applications are shown to present the versatility and flexibility of the crowd rendering engine.

Crowds for interactive virtual environments

Branislav Ulicny

Crowds are part of our everyday experience; nevertheless, in virtual worlds they are still relatively rare. In this thesis we explore the challenges of bringing crowds into interactive virtual environments and the possible applications of real-time interactive crowds, for example, in the domains of virtual heritage and training systems. We address several topics including real-time generation of higher-level behaviors, lower-level motion control for many characters, management of variety, integration of crowds into virtual environments, interaction with virtual crowds and authoring of scenarios. In comparison with the other crowd modeling approaches, we focus on more complex behaviors of many agents in dynamic environments with possible user interaction. In our system a crowd is modeled as a collection of individuals which react to the environment, to other agents and to real human participants of the simulation and can have very different behaviors, both for one agent in different situations, and for many agents in the same situation. We emphasize the importance of variety as one of the most distinguishing features of the crowd simulations; we introduce the notion of levels-of-variety. We address as well the question of how to author crowd scenes in an efficient way. We introduce a novel approach to create complex scenes involving thousands of animated individuals in a simple and intuitive way. By employing a brush metaphor, analogous to the tools used in image manipulation programs, we can distribute, modify and control crowd members in real-time with immediate visual feedback. We demonstrate the validity of our behavior simulation approach with several case studies, where we use our crowd system to manage crowd behaviour in a virtual reality training system and virtual heritage reconstruction. The potential of our authoring approach is shown by authoring a scenario of a virtual audience in a theater and a scenario of a pedestrian crowd in a city.

EPFL2005

Simulating interactions with virtual characters for the treatment of social phobia

Helena Stephanie Grillon Le Gallennec

Virtual Reality (VR) has nowadays become a very useful tool for therapists in the treatment of phobias. Indeed, it allows the simulation of scenarios which are difficult to reproduce in real life. It also allows for a situation to be repeated as much as one wants. Moreover, it allows for a complete control over the situation. The simulation can be stopped if the patient cannot handle it. It can also be tweaked for gradual exposure. Virtual Reality Exposure Therapy (VRET) has proven to be efficient in the context of phobias such as acrophobia or the fear of flying. Social phobia, however, are much harder to deal with. Indeed, as humans, we are experts in human representations and behaviors; it makes it much harder to obtain credible and immersive environments. In this thesis, we describe a set of tools and applications which we have developed to be used in VRET of social phobia and agoraphobia with crowds. We first describe how we create different scenarios for VRET of social phobia. We then expose the application we have developed which allows for elaborate interactions between a user and virtual characters. In particular, we have designed and implemented a software which allows for virtual characters to change behavior depending on the user's eye contact behavior. It allows them to seem interested when being looked at and distracted when not. We then describe the model we have implemented to simulate gaze attention behaviors for crowds of virtual characters. This consists of a method that automatically detects where and when each virtual character in a crowd should look. Secondly, it consists of a dedicated gaze Inverse Kinematics (IK) solver in order for the virtual characters to satisfy the constraints defined by the automatically detected points to be looked at. This allows for the characters to perform the looking motion in a natural and human like way. We then describe the architecture we have developed to combine the work we have done in the domain of social phobia and this model of attention behaviors for crowd characters. We thus use our model of looking behaviors to allow for crowd characters to look at each other. We also use eye-tracking and optical motion capture to determine where a user is looking in a CAVE environment. The virtual characters then respond by either looking at the user, looking at what the user is looking at, or looking at other characters in the crowd. We thus obtain an immersive and interactive environment for VRET in the domain of agoraphobia with crowds. The third part of this thesis describes various experiments we have conducted in order to validate our applications. Our first study consists of using VR in a head-mounted display (HMD) for the treatment of social phobia. In this study, we also use eye-tracking in order to analyze eye contact avoidance behaviors before and after therapy. We then discuss the use of eye-tracking as a tool to help assess and diagnose social phobia. Since eye contact avoidance behaviors are frequent in people suffering from such phobias, eye-tracking can certainly be a helpful tool. We describe an experiment in which we tested eye-tracking as a diagnosis and assessment tool on a phobic population and on a control group. We also describe an experiment to evaluate the potential of our proposed interaction loop in the context of social phobia. Finally, we describe the experiment we have conducted to evaluate our application in the context of agoraphobia with crowds.

EPFL2009

Crowds for interactive virtual environments

Branislav Ulicny

EPFL2005

Simulating interactions with virtual characters for the treatment of social phobia

Helena Stephanie Grillon Le Gallennec

EPFL2009