Calculating detailed solar shading and overshadowing is a problem for most building analysis tools, ECOTECT included. It is important to a whole range of building performance criteria, from thermal and daylighting analysis through to solar access and rights-to-light. However, to do it properly can take a frustratingly long time. This article explains exactly what is happening during these calculations and offers tips on how to optimise the process and make best use of your existing shading data.