Ecotect from Square One Research is a building performance analysis and design tool that includes a 3D modeller that can export to Radiance. It is available only for the Windows operative system.
A typical Radiance session would be:
Ecotect, set location, materials properties.Radiance Control Panel, set sky, resolution, analysis configuration.Radiance Image Viewer.
The Radiance Control Panel and '‘Radiance Image viewer are free and available from http://www.squ1.com/downloads and http://squ1.com/projects/freeware
It is necessary to have Desktop Radiance or other Radiance binaries for windows installed, like the MinGW ones.