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Our approach generalizes the anisotropic monodisperse micrograin model We first reformulate it in a non\u2010axis\u2010aligned configuration, allowing for the later combination of different micrograin types elongated in arbitrary directions. We then extend the monodisperse model to the polydisperse case, deriving its three key components: (i) a general filling factor that controls the mix between micrograins and the bulk medium; (ii) an exact normal distribution function for surfaces composed of polydisperse micrograin distributions; and (iii) the corresponding fully\u2010correlated shadowing and masking term. This results in an analytical single\u2010scattering BSDF for discrete polydisperse surface materials, validated over ground truth simulations, for which we also derive a dedicated importance sampling procedure. Our model supports varying heights and anisotropy orientations of different micrograin types as input, giving additional control to simulate phenomena like retro\u2010reflection from mixed materials, color mixture depending on lighting and observation directions, multiple directions of anisotropy, etc.<\/jats:p>","DOI":"10.1111\/cgf.70387","type":"journal-article","created":{"date-parts":[[2026,3,30]],"date-time":"2026-03-30T12:45:29Z","timestamp":1774874729000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A Discrete Polydisperse Anisotropic BSDF Model based on the Micrograin Framework"],"prefix":"10.1111","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-2219-5407","authenticated-orcid":false,"given":"K.","family":"Xu","sequence":"first","affiliation":[{"name":"Universit\u00e9 de Poitiers, CNRS XLIM UMR 7252  France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-6134-7668","authenticated-orcid":false,"given":"S.","family":"Lucas","sequence":"additional","affiliation":[{"name":"Inria  France"},{"name":"Universit\u00e9 C\u00f4te d'Azur  France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2964-2608","authenticated-orcid":false,"given":"M.","family":"Ribardi\u00e8re","sequence":"additional","affiliation":[{"name":"Universit\u00e9 de Poitiers, CNRS XLIM UMR 7252  France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8992-4458","authenticated-orcid":false,"given":"B.","family":"Bringier","sequence":"additional","affiliation":[{"name":"Universit\u00e9 de Poitiers, CNRS XLIM UMR 7252  France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2844-6656","authenticated-orcid":false,"given":"P.","family":"Barla","sequence":"additional","affiliation":[{"name":"Inria  France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2026,3,30]]},"reference":[{"issue":"4","key":"e_1_2_11_2_2","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1111\/cgf.14590","article-title":"Microsurface transformations","volume":"41","author":"Atanasov A.","year":"2022","journal-title":"Computer Graphics Forum"},{"issue":"2","key":"e_1_2_11_3_2","doi-asserted-by":"crossref","first-page":"15:1","DOI":"10.1145\/3406183","article-title":"\ua7fbLIP: A Difference Evaluator for Alternating Images","volume":"3","author":"Andersson P.","year":"2020","journal-title":"Proceedings of the ACM on Computer Graphics and Interactive Techniques"},{"key":"e_1_2_11_4_2","doi-asserted-by":"crossref","unstructured":"AshikminM. 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