The diagram below provides a forward-looking high level overview of a full PX4 onboard and offboard stack. The left hand side shows one possible hardware configuration with a flight controller (light blue) connected to a perception computer (dark blue) via RTPS. The perception computer provides vision control and object avoidance using a camera sensor array, and has a separate payload camera.
The right hand side of the diagram shows the end-to-end software stack. The stack "approximately" aligns horizontally with the hardware parts of the diagram, and is colour-coded to show which software is running on the flight controller and which on the companion computer.