A toolbox for creation and rendering of dynamic virtual acoustic environments (TASCAR) that allows direct user interaction was developed for application in hearing aid research and audiology. This technical paper describes the general software structure and the time-domain simulation methods, i.e., transmission model, image source model, and render formats, used to produce virtual acoustic environments with moving objects. Implementationspecific properties are described, and the computational performance of the system was measured as a function of simulation complexity. Results show that on commercially available commonly used hardware the simulation of several hundred virtual sound sources is possible in the time domain.