Mit­suba is a re­search-ori­ented ren­der­ing sys­tem writ­ten in cross-plat­form C++. Its code is ex­tremely mod­u­lar, con­sist­ing of a small set of core lib­rar­ies and over 100 dif­fer­ent plu­gins that im­ple­ment func­tion­al­ity ran­ging from ma­ter­i­als and light sources to com­plete ren­der­ing al­gorithms. A strong em­phas­is is placed on scalab­il­ity and par­al­lel­ism; Mit­suba has been used to render com­plex scenes us­ing over a thou­sand net­worked cores at the same time.