Mechanisms for externally directing graphics processing unit data are disclosed. A simulator module includes an external application interface that is configured to communicate with an external application that is independent of the simulator module. The simulator module is configured to receive from the external application via the external application interface first user data and provide the first user data to a graphics processing unit (GPU) for use by a first shader function for image rendering during a first period of time. The simulator module continuously generates simulation data associated with a simulation and provides the simulation data to the GPU for the image rendering during the first period of time.