From Edo Culture: Daily Life and Diversions in Urban Japan, 1600–1868, by Nishiyama Matsunosuke, trans. and ed. by Gerald Groemer (U. Hawai‘i Press, 1997), pp. 70-71:
Gennai, who was well versed in Western art and painted in oils himself, was surrounded by a cultural group whose role in Edo-period culture can hardly be overestimated. Gennai’s coterie included scholars of Western learning, doctors practicing Dutch-style medicine, scholars of Chinese literature, calligraphers, and many others. The interaction of these men led to the creation of a number of ukiyo-e and books.
Nishiki-e were an artistic development that stood in sharp contrast to earlier Japanese prints. In Japanese painting before the age of nishiki-e, empty space was charged with great meaning. Use of blank areas was deeply related to the Buddhist notions of emptiness (kū), to specifically Japanese ideas of space (ma), and to Japanese philosophies of nature. These concepts are in turn related to the idea of nothingness (mu) found in Eastern thought in general. From the time of Harunobu’s nishiki-e, however, virtually the entire surface of the picture was filled with color. Moreover, many nishiki-e employed Western techniques of perspective. This denial of the Eastern concept of mu and departure from the design and coloration of previous Japanese pictorial art was in part the result of a familiarity with Western techniques of oil painting and copperplate etching. Not everything was taken from these sources, but the works of Harunobu, Haruaki, Sharaku, Utamaro, and Hokusai unambiguously show such influence. These men (with the possible exception of Sharaku) often attended the daishōkai [calendar designing and printing events] and were good friends with Hiraga Gennai, Shiba Kōkan, and Gennai’s outstanding disciple Morishima Chūryō.
The establishment of nishiki-e with perspective within the context of traditional “flat” Japanese painting was an epoch-making event in the history of Japanese pictorial art. Western techniques had here been completely absorbed into Japanese culture. Although the roots of these techniques could be traced back a century and a half to Western influence at the start of the Edo period. Western procedures now reemerged as something entirely new. Nishiki-e met with such unusual acclaim by the Japanese commoner population because Western techniques had been so thoroughly assimilated.
This process of assimilation also led to the nishiki-e fads in Europe and the United States. From the end of the Edo period to the early years of the Meiji era, a tremendous number of nishiki-e masterpieces were sold to foreigners. The works of Hokusai, which were perhaps the most Western in tone, were especially prized and often became the subject of scholarly studies.