Realistic following behaviors for crowd simulation

International audienceWhile walking through a crowd, a pedestrian experiences a large number of interactions with his neighbors. The nature of these interactions is varied, and it has been observed that macroscopic phenomena emerge from the combination of these local interactions. Crowd models have hitherto considered collision avoidance as the unique type of interactions between individuals, few have considered walking in groups. By contrast, our paper focuses on interactions due to the following behaviors of pedestrians. Following is frequently observed when people walk in corridors or when they queue. Typical macroscopic stop-and-go waves emerge under such traffic conditions. Our contributions are, first, an experimental study on following behaviors, second, a numerical model for simulating such interactions, and third, its calibration, evaluation and applications. Through an experimental approach, we elaborate and calibrate a model from microscopic analysis of real kinematics data collected during experiments. We carefully evaluate our model both at the microscopic and the macroscopic levels. We also demonstrate our approach on applications where following interactions are prominent

Planning Human Walk in Virtual Environments

This paper presents a method for animating human characters, especially dedicated to walk planning problems. The method is integrated in a randomized motion planning scheme, including a steering method dedicated to human walk. This steering method integrates a character motion controller assuming realistic animations. The navigation of the character through the virtual environment is modeled as a composition of Bezier curves. The controller is based on motion capture data editing techniques. This approach satisfies some essential computer graphics criteria : realistic result, low response time, collision-free motion in possibly constrained 3D environments. The approach has been implemented and successfully demonstrated on several examples

Guided by gaze: Prioritization strategy when navigating through a virtual crowd can be assessed through gaze activity

Modelling crowd behavior is essential for the management of mass events and pedestrian traffic. Current microscopic approaches consider the individual's behavior to predict the effect of individual actions in local interactions on the collective scale of the crowd motion. Recent developments in the use of virtual reality as an experimental tool have offered an opportunity to extend the understanding of these interactions in controlled and repeatable settings. Nevertheless, based on kinematics alone, it remains difficult to tease out how these interactions unfold. Therefore, we tested the hypothesis that gaze activity provides additional information about pedestrian interactions. Using an eye tracker, we recorded the participant's gaze behavior whilst navigating through a virtual crowd. Results revealed that gaze was consistently attracted to virtual walkers with the smallest values of distance at closest approach (DCA) and time to closest approach (TtCA), indicating a higher risk of collision. Moreover, virtual walkers gazed upon before an avoidance maneuver was initiated had a high risk of collision and were typically avoided in the subsequent avoidance maneuver. We argue that humans navigate through crowds by selecting only few interactions and that gaze reveals how a walker prioritizes these interactions. Moreover, we pose that combining kinematic and gaze data provides new opportunities for studying how interactions are selected by pedestrians walking through crowded dynamic environments.FWN – Publicaties zonder aanstelling Universiteit Leide

Continuous Level of Detail for Large Scale Rendering of 3D Animated Polygonal Models

Current simulation applications are mainly focused on the efficient management of scenarios with static objects. However, managing dynamic objects, such as animated characters, is very different and requires more specific processing methods which tend to have a high computational cost. Recent advances in graphics hardware offer more ways to improve the performance of these scenes. In this paper, we introduce a new method for rendering large crowds of animated characters at interactive frame rates. Our method is a fully-GPU hybrid combination of mesh instancing, continuous level of detail and hardware palette skinning. Thus, we take advantage of mesh instancing to render multiple instances of a given mesh belonging to a continuous level of detail model, avoiding the typical popping artifacts existing on previous approaches. We finally obtained a low storage cost, performance improvements when applying level of detail and mesh instancing techniques and, moreover, a minimization of the overhead produced by animating

An Analysis of Motion Blending Techniques

Abstract. Motion blending is a widely used technique for character animation. The main idea is to blend similar motion examples according to blending weights, in order to synthesize new motions parameterizing high level characteristics of interest. We present in this paper an in-depth analysis and comparison of four motion blending techniques: Barycentric interpolation, Radial Basis Function, K-Nearest Neighbors and Inverse Blending optimization. Comparison metrics were designed to measure the performance across different motion categories on criteria including smoothness, parametric error and computation time. We have implemented each method in our character animation platform SmartBody and we present several visualization renderings that provide a window for gleaning insights into the underlying pros and cons of each method in an intuitive way.

Gap flow in an Alpine valley during a shallow south föhn event: Observations, numerical simulations and hydraulic analogue

International audienceThis paper examines the three-dimensional structure and dynamics of southerly hybrid gap/mountain ow through the Wipp valley (Wipptal), Austria, observed on 30 October 1999 using high-resolution observations and model simulations. The observations were obtained during a shallow south föhn event documented in the framework of the Mesoscale Alpine Programme (MAP). Three important data sources were used: the airborne differential-absorption lidar LEANDRE 2, the ground-based Doppler lidar TEACO2 and in situ measurements from the National Oceanic and Atmospheric Administration P-3 aircraft. This event was simulated down to 2 km horizontal resolution using the non-hydrostatic mesoscale model Meso-NH. The structure and dynamics of the ow were realistically simulated. The combination of high-resolution observations and numerical simulations provided a comprehensive three-dimensional picture of the ow through the Wipptal: in the gap entrance region (Brenner Pass, Austria), the low-level jet was not solely due to the channelling of the southerly synoptic ow through the elevated gap. Part of the Wipptal ow originated as a mountain wave at the valley head wall of the Brenner Pass. Downstream of the pass, the shallow föhn ow had the characteristics of a downslope windstorm as it rushed down towards the Inn valley (Inntal) and the City of Innsbruck, Austria. Downhill of the Brenner Pass, the strongest ow was observed over a small obstacle along the western side wall (the Nösslachjoch), rather than channelled in the deeper part of the valley just to the east. Further north, the low-level jet was observed in the centre of the valley. Approximately halfway between Brenner Pass and Innsbruck, where the along-axis direction of the valley changes from north to north-northwest , the low-level jet was observed to be de ected to the eastern side wall of the Wipptal. Interaction between the Stubaier Alpen (the largest and highest topographic feature to the west of the Wipptal) and the south-westerly synoptic ow was found to be the primary mechanism responsible for the dee ection. The along-and cross-valley structure and dynamics of the ow were observed to be highly variable due to the in uence of surrounding mountains, localized steep slopes within the valley and outt ows from tributaries (the Gschnitztal and the Stubaital) to the west of the Wipptal. For that shallow föhn case, observations and simulations provided a large body of evidence that downslope ow created thinning/ thickening uid and accelerations/ decelerations reminiscent of mountain wave/hydraulic theory. Along the Wipptal, two hydraulic-jump-like transitions were observed and simulated, (i) on the lee slope of the Nösslachjoch and (ii) in the Gschnitztal exit region. A hydraulic solution of the ow was calculated in the framework of reduced-gravity shallow-water theory. The down-valley evolution of the Froude number computed using LEANDRE 2, P-3 ight level and TEACO2 measurements conn rmed that these transitions were associated with super-to subcritical transitions