We present a system allowing real-time image based lighting based on HDR panoramic images. The system performs time-consuming diffuse light calculations in a preprocessing step; which is key to attaining interactivity. The real-time subsystem processes an image based lighting model in software; which would be simple to implement in hardware. Rendering is handled by OpenGL; but could be substituted for another graphics API. Applications for the technique presented are discussed; and includes methods for realistic outdoor lighting. The system architecture is outlined; describing the algorithms used.