Keywords: discrete-event simulation, visualization, post-processed animation, concurrent animation, visual interactive simulation, construction operations.

The current state-of-the-art in discrete-event simulation (DES) allows for the accurate modeling of a wide variety of complex construction operations. With recent advances in visualizing simulated construction operations, it is now possible to obtain accurate and realistic post-processed animations of simulated construction operations. Given these advances, current research efforts are underway to integrate current systems (simulation and animation) to build DES-based Virtual Reality (VR) systems for construction. This paper presents an overview of the work accomplished to enable concurrent simulation-animations of construction operations, which is the first major component required to build DES-based VR systems.

The difference between current systems and the proposed system is runtime user interaction with simulation models, i.e. the ability for users to change the course of the simulation in real-time. Concurrent simulation-animation or concurrent animation provides the foundation to make user interaction possible, which is not possible with the post-processed animation paradigm that is currently available.

The challenge in enabling concurrent simulation-animation (or concurrent animation) is the design of a time advance algorithm that is capable of synchronizing the internal clocks of simulation and animation systems. This is particularly challenging because each system employs a radically different time-advance mechanism. The simulation clock advances in discrete uneven time steps while the animation clock advances in a near continuous manner. In addition, this synchronization must be done such that simulation does not advance ahead of the animation.

This paper provides a brief and comprehensive overview of the current techniques available and employed to visualize simulated construction operations. The paper then discusses the time-advance mechanisms employed by simulation and animation systems by briefly explaining their algorithms. Finally, the paper presents the manner in which a concurrent simulation-animation clock must work and the conceptual design of the time-advance algorithm that achieves the required synchronization. In conclusion, this paper shows that it is possible to enable concurrent animation for discrete-event simulation.

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