Evalglare (see the PDF at http://www.radiance-online.org/learning/documentation/manual-pages/pdfs/evalglare.pdf) calculates DGI, as well as several other daylight metrics, and it is now part of the NREL Radiance distribution. If you're using it as a design tool as well as to satisfy Chinese code requirements, I recommend looking at DGP.

Evalglare (see http://www.radiance-online.org/learning/documentation/manual-pages/pdfs/evalglare.pdf) calculates DGI, as well as several other daylight metrics, and it is now part of the NREL Radiance distribution. If you're using it as a design tool as well as to satisfy Chinese code requirements, I recommend looking at DGP.