This paper presents a new software architecture for 3D mixed reality applications, named Tinmith-evo5. Currently there are a limited number of existing toolkits for the development of 3D mixed reality applications, each optimised for a particular feature but at the detriment of others. Complex interactive user interfaces and applications require extensive supporting infrastructure, and can be hampered by inadequate support. The Tinmith-evo5 architecture is optimised to develop mobile augmented reality and other interactive 3D applications on portable platforms with limited resources. This architecture is implemented in C++ with an object-oriented data flow design, an object store based on the Unix file system model, and uses other ideas from existing previous work.