Discrete Stochastic Microfacet Models

In ACM Transactions on Graphics (Proceedings of SIGGRAPH 2014)

Left: fancy pair of wo­men’s dress shoes with a glit­tery fin­ish modeled us­ing our dis­crete mi­cro­fa­cet BRDFRight: Christ­mas or­na­ments il­lus­trat­ing a range of mod­el para­met­ers in­clud­ing dif­fer­ent particle counts, sur­face rough­ness, and an­iso­tropy.


This pa­per in­vest­ig­ates ren­der­ing glit­tery sur­faces, ones which ex­hib­it shift­ing ran­dom pat­terns of glints as the sur­face or view­er moves. It ap­plies both to dra­mat­ic­ally glit­tery sur­faces that con­tain mir­ror-like flakes and also to rough sur­faces that ex­hib­it more subtle small scale glit­ter, without which most glossy sur­faces ap­pear too smooth in close-up. These phe­nom­ena can in prin­ciple be sim­u­lated by high-res­ol­u­tion nor­mal maps, but maps with tiny fea­tures cre­ate severe ali­asing prob­lems un­der nar­row-angle il­lu­min­a­tion. In this pa­per we present a stochast­ic mod­el for the ef­fects of ran­dom sub­pixel struc­tures that gen­er­ates glit­ter and spa­tial noise that be­have cor­rectly un­der dif­fer­ent il­lu­min­a­tion con­di­tions and view­ing dis­tances, while also be­ing tem­por­ally co­her­ent so that they look right in mo­tion. The mod­el is based on mi­cro­fa­cet the­ory, but it re­places the usu­al con­tinu­ous mi­cro­fa­cet dis­tri­bu­tion with a dis­crete dis­tri­bu­tion of scat­ter­ing particles on the sur­face. A nov­el stochast­ic hier­archy al­lows ef­fi­cient eval­u­ation in the pres­ence of large num­bers of ran­dom particles, without ever hav­ing to con­sider the particles in­di­vidu­ally. This leads to a multiscale pro­ced­ur­al BRDF that is read­ily im­ple­men­ted in stand­ard ren­der­ing sys­tems, and which con­verges back to the smooth case in the lim­it.



Text citation

Wenzel Jakob, Miloš Hašan, Ling-Qi Yan, Jason Lawrence, Ravi Ramamoorthi, and Steve Marschner. 2014. Discrete Stochastic Microfacet Models. In ACM Transactions on Graphics (Proceedings of SIGGRAPH) 33(4). 115:1–115:10.

    author = {Wenzel Jakob and Miloš Hašan and Ling-Qi Yan and Ravi Ramamoorthi and Steve Marschner},
    title = {Discrete Stochastic Microfacet Models},
    journal = {ACM Transactions on Graphics (Proceedings of SIGGRAPH)},
    volume = {33},
    number = {4},
    pages = {115:1--115:10},
    year = {2014},
    month = jul,
    doi = {10.1145/2601097.2601186}