In the design phase and while materials, the position of the sun and raytracing settings for the scene are still being modified, it can be helpful to only process certain parts of the 3D view to check the results of raytracing. Otherwise, the whole scene would have to be processed, which according to settings could take some time, to only then find that certain details are perhaps too bright or too dark. To achieve this use the “Raytrace detail” function provided in the 3D view tool bar.
After clicking on the appropriate button the function requires a rectangle to be entered in the 3D view. Once a rectangle has been defined, processing starts automatically for the detail using the current settings for raytracing.