Discrete-event material flow simulation tools are already offering possibilities to visualize factory operations in virtual worlds. This feature allows less experienced users to analyze the underlying system. Beyond this, visualization is not used to interact with the simulated (underlying) system to improve or control the material flow under disturbances. This paper presents a simulation-based two-tier framework, which seeks to control or improve material flow by means of user immersive visualization. The first tier uses optimization to compute the material flow
based on deterministic disturbances. The second tier is a reactive algorithm, which computes solutions for probabilistic disturbances. The results of the two tiers are used for interacting with the underlying system using visualization. We show conceptually that it is possible to integrate real-time decision making in virtual simulation environments.