An important challenge in virtual environment applications is to steer virtual characters through complex and dynamic worlds. The characters should be able to plan their paths and move toward their desired locations, avoiding at the same time collisions with the environment and with other moving entities. In this paper we propose a general method for realistic path planning, the Indicative Route Method (irm). In the irm, a so-called indicative route determines a global route for the character, whereas a corridor around this route is used to handle a broad range of other path planning issues, such as avoiding characters and computing smooth paths. As we will show, our method can be used for real-time navigation of many moving characters in complicated environments. It is fast, flexible and generates believable paths.

A central problem in games is planning high-quality paths for characters avoiding obstacles in the environment. Current games require a path planner that is fast (to ensure real-time interaction) and flexible (to avoid local hazards). In addition, a path needs to be natural, meaning that the path is smooth, short, keeps some clearance to obstacles, avoids other characters, etcetera. Game worlds are normally populated with a large number of characters. In this paper we show how the recently introduced Corridor Map Method can be extended and used to efficiently compute smooth motions for these characters. We will consider crowds in which the characters wander around, characters have goals, and characters behave as a coherent group. The approach is very fast. Even in environments with 5000 characters it uses only 40 % of the processing power of a single core of a cpu. Also the resulting paths are indeed natural.

Abstract — Virtual characters often need to plan visually convincing paths through a complicated environment. For example, a traveler may need to walk from an airport entrance to a staircase, descend the staircase, walk to a shuttle, ride the shuttle to a destination, ride an elevator back to the ground floor, and finally move on the ground floor again to reach the desired airplane. Most previous research only supports path planning in a single plane because the underlying data structures are two-dimensional. The goal of this paper is to permit visually convincing paths to be efficiently computed in a multi-layered environment such as an airport or a multistorey building. We describe an algorithm to create a navigation mesh, and our implementation demonstrates the feasibility of the approach. A multi-layered environment is represented by a set of twodimensional layers and a set of connections. Each layer is a collection of two-dimensional polygons that all lie in a single plane, and each connection provides a means of moving between layers. We first compute the traditional medial axis of each twodimensional layer in the environment. The connections are then used to iteratively merge this collection of medial axes into a single data structure. By adding a linear number of line segments to this structure, we obtain a navigation mesh that mathematically describes the walkable areas in a multilayered environment. This mesh can easily be input into existing planners to generate visually convincing paths for thousands of virtual characters in real-time. I.

Abstract. Path planning is a central problem in virtual environments and games. When computer-controlled characters move around in virtual worlds they have to plan their paths to desired locations. These paths must avoid collisions with the environment and with other moving characters. Also a chosen path must be natural, meaning that it is the kind of path a real human being could take. The algorithms for planning such paths must be able to handle hundreds of characters in real-time and must be flexible. The Corridor Map Method (cmm) was recently introduced as a flexible path planning method in interactive virtual environments and games. The method is fast and flexible and the resulting paths are reasonable. However, the paths tend to take unnatural turns when characters get close to other characters or small obstacles. In this paper we will improve on the cmm by decoupling collision avoidance with the environment and local steering behavior. The result is a method that keeps the advantages of the cmm but has much more natural steering. Also the method allows for more flexibility in the desired routes of the characters.

Abstract. Planning high-quality camera motions is a challenging problem for applications dealing with interactive virtual environments. This challenge is caused by conflicting requirements. On the one hand we need good motions, formed by trajectories that are collision-free and keep the character that is being followed in clear view. On the other hand, we need frame coherence, i.e. the view must change smoothly such that the viewer does not get disoriented. Since camera motions dynamically evolve, good motions may require the camera to jump, leading to a broken frame coherence. Hence, a careful trade-off must be made. In addition to this challenge, interactive applications require real-time computations, preventing an exhaustive search for ‘the best ’ solution. We propose a new method for planning camera motions which tackles this trade-off in real-time. The method can be used for planning camera motions of npc’s and first-person characters. Experiments show that high-quality camera motions are obtained for both scenarios in real-time. 1

Virtual characters often need to plan visually convincing paths through a complicated environment. For example, a traveler may need to walk from an airport entrance to a staircase, descend the staircase, walk to a shuttle, ride the shuttle to a destination, ride an elevator back to the ground floor, and finally move on the ground floor again to reach the desired airplane. Most previous research only supports path planning in a single plane because the underlying data structures are two-dimensional. The goal of this paper is to permit visually convincing paths to be efficiently computed in a multi-layered environment such as an airport or a multistorey building. We describe an algorithm to create a navigation mesh, and our implementation demonstrates the feasibility of the approach. A multi-layered environment is represented by a set of two-dimensional layers and a set of connections. Each layer is a collection of two-dimensional polygons that all lie in a single plane, and each connection provides a means of moving between layers. We first compute the traditional medial axis of each twodimensional layer in the environment. The connections are then used to iteratively merge this collection of medial axes into a single data structure. By adding a linear number of line segments that connect the medial axis to the nearest obstacles, we obtain a navigation mesh that mathematically describes the walkable areas in a multi-layered environment. This mesh can easily be input into existing planners to generate visually convincing paths for thousands of characters in real-time. 1

Abstract not found

Virtual characters in games and simulations often need to plan visually convincing paths through a crowded environment. This paper describes how crowd density information can be used to guide a large number of characters through a crowded environment. Crowd density information helps characters avoid congested routes that could lead to traffic jams. It also encourages characters to use a wide variety of routes to reach their destination. Our technique measures the desirability of a route by combining distance information with crowd density information. We start by building a navigation mesh for the walkable regions in a polygonal 2D or multi-layered 3D environment. The skeleton of this navigation mesh is the medial axis. Each walkable region in the navigation mesh maintains an up-to-date density value, given by the fraction of the area that is being occupied by characters. These density values are mapped onto the medial axis to form a weighted graph. An A * search on this graph yields a backbone path for each character, and forces are used to guide the characters through the weighted environment. The characters periodically replan their routes as the density values are updated. Our experiments show that we can compute congestionavoiding paths for tens of thousands of characters in real-time. 1