An image-based approach to the rendering of crowds in real-time

The wide use of computer graphics in games, entertainment, medical, architectural and cultural applications, has led it to becoming a prevalent area of research. Games and entertainment in general have become one of the driving forces of the real-time computer graphics industry, bringing reasonably realistic, complex and appealing virtual worlds to the mass-market. At the current stage of technology, an user can interactively navigate through complex, polygon-based scenes rendered with sophisticated lighting, at times interacting with Al-based synthetic characters or virtual humans. As the size and complexity of the environments continuously increase, there is a growing need to add common real-life phenomenons such as the presence of crowds. Rendering highly populated urban environments requires a good synthesis of two partially overlapping problems: the management of vast and detailed environments, and the visualisation of large-scale crowds. While in the past a large amount of research has gone into the investigation of optimisation strategies and speed-up methods dedicated to large and static polygonal models, real-time visualisation of animated crowds poses novel challenges due to the computational power needed to visualize a multitude of animated characters scenarios where thousands of characters are on-screen simultaneously can easily lead to polygon budgets exceeding millions of triangles, that are hardly possible to render at interactive frame-rates even on the most powerful graphics technology available today. The present thesis extensively investigates this topic, and proposes the usage of an image-based data representation in order to speed-up rendering of animated characters so to achieve interactive frame-rates even when crowds composed by thousands of individuals are on-screen. We advance over the state of the art in this field introducing a novel form of impostor rendering techniques for animated crowds, and presenting methods that exploit this novel form of representation to handle also advanced rendering effects such as crowd lighting and shadowing we also discuss the important aspects of compatibility of our new method with existing polygonal based scene-graphs architectures. The results are showing that real-time crowd rendering is an application scenario where the introduction of Image Based Rendering methods can truly be beneficial, making possible the rendering of crowds composed by thousands of individual in real time in any existing rendering software framework even on commodity hardware