Now to be clear, you do not need to buy the product to take advantage of the videos. The product is there to provide additional examples based on the content of the videos. But you could do that for yourself. Given time.
The fabric materials look outstanding. You're a master of the DTE.
From the outstanding videos David made, I compiled a more theoretical document covering the complete DTE. As agreed with DAZ in February 2011, this compilation will be added as appendix to the official Bryce 7.1 documentation. Until the documentation materializes, the DTE doc can be downloaded separately from here: http://www.horo.ch/raytracing/tuts/pdf/DTEdoc.zip - Please note that this service will be discontinued once the Bryce 7.1 documentation is available. The zipped file is 21 MB and contains the PDF containing over 900 ppictures on 84 pages.