Abstract: Apparatus and methods are disclosed for providing virtual bags that can be used to simulate and quantify performance of different explosive detection system architectures. The virtual bags can be provided to a simulator for designing and simulating operation of imaging scanners, including X-ray and millimeter-wave based threat detection equipment deployed in transit facilities and other secure locations. One example method of generating container models for a container inspection system includes generating a plurality of objects using a probability function; generating a respective position, scale, and orientation for each of the objects within a container having a defined boundary; generating pairings for a respective material for each of the objects using a probability function; and storing a container instance indicating at least one of: the generated pairings, the respective object positions, object scales, object orientation, the objects, or the respective materials in a computer-readable storage device.