3.5.7.10 Duty Cycle The Duty Cycle setting is provided only for unusual cases of heat accumulation. It is not intended to be used in other circumstances (as it offers little benefit other than as described below). Unless you are using a laptop in a restricted environment (or perhaps in orbit), this menu will be of little interest to you. Some computers - particularly laptops or notebooks - cool their CPU's by convection. No CPU fan is used. This can make this type of device prone to overheating in certain circumstances (for example, where circulation of air is restricted, such as in a confined space, or where hot air does not, by its nature, rise, such as in zero-gravity). POV-Ray makes extensive use of a processor's Floating Point Unit (FPU), a portion of the CPU that is not normally prone to high activity over long periods. Such use can potentially cause the CPU to generate more heat. Additionally, high CPU activity can cause the unit's normal heat-reducing facilities (such as lower-power CPU modes) to be inactive. The Duty Cycle setting is used to tell POV-Ray to only use a certain percentage of the CPU's available time, even if nothing else is competing for the CPU. For example, a duty cycle of 10% would cause POV-Ray, during a render, to sleep for 90% of the available time, and only render during 10% of it. During rendering, if the duty cycle is not set to 100% (the default), POV-Ray will update the status bar at the bottom of the window if it is in sleep mode. This update will show how many seconds remain until rendering starts again (which is based around a ten-second cycle). For example, a duty cycle of 70% would see POV-Ray render for seven seconds, then sleep for three. While it may seem far-fetched to include a feature in POV-Ray that seems primarily to be of use in zero-gravity, it in fact is for this exact reason it is here. On 25 April 2002, African entrepreneur Mark Shuttleworth was blasted into space in a Russian Soyuz capsule. Accompanying Mark on this launch was a copy of POV-Ray for Windows v3.5 beta 15, and a special scene written for the purpose by two of the word's best POV-Ray artists. Whilst on the International Space Station, Mark rendered a 6000x8000 pixel version of that scene. This scene is now available as a poster; see our website for more information and purchasing options.