Abstract
Complex specular microstructures found in glittery, scratched or brushed metal materials exhibit high-frequency variations in reflected light intensity. These variations are important for the human eye and give materials their uniqueness and personality. To model such microsurfaces, high-definition normal maps are very effective. The works of Yan et al. (ACM Trans Graph 33(4):116:1–116:9, 2014; ACM Trans Graph 35(4):56:1–56:9, 2016) enable the rendering of such material representations by evaluating a microfacet-based BRDF related to a whole ray footprint. Still, in specific configurations and especially at grazing angles, their method does not fully capture the expected material appearance. We propose to build upon their work and tackle the problem of accuracy using a more physically based reflection model. To do so, the normal map is approximated with a mixture of anisotropic, noncentered Beckmann normal distribution functions from which a closed form for the masking–shadowing term can be derived. Based on our formal definition, we provide a fast approximation leading to a performance overhead varying from 5 to 20% compared to the method of Yan et al. (2016). Our results show that we more closely match ground truth renderings than their methods.
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References
Atanasov, A., Koylazov, V.: A practical stochastic algorithm for rendering mirror-like flakes. In: ACM SIGGRAPH 2016 Talks, SIGGRAPH ’16, pp. 67:1–67:2. ACM, New York (2016)
Belcour, L., Yan, L.Q., Ramamoorthi, R., Nowrouzezahrai, D.: Antialiasing complex global illumination effects in path-space. ACM Trans. Graph. 36(1), 9:1–9:13 (2017)
Bosch, C., Patow, G.: Real-time path-based surface detail. Comput. Graph. 34(4), 430–440 (2010). Procedural methods in computer graphics illustrative visualization
Bosch, C., Pueyo, X., Mérillou, S., Ghazanfarpour, D.: A physically based model for rendering realistic scratches. Comput. Graph. Forum 23(3), 361–370 (2004)
Dupuy, J., Heitz, E., Iehl, J.C., Poulin, P., Neyret, F., Ostromoukhov, V.: Linear efficient antialiased displacement and reflectance mapping. ACM Trans. Graph. 32(6), 211:1–211:11 (2013)
Han, C., Sun, B., Ramamoorthi, R., Grinspun, E.: Frequency domain normal map filtering. ACM Trans. Graph. 26(3), 28 (2007)
Heckbert, P.S.: Fundamentals of texture mapping and image warping. Master’s thesis (1989)
Heitz, E.: Understanding the masking–shadowing function in microfacet-based BRDFs. J. Comput. Graph. Tech. 3(2), 48–107 (2014)
Igehy, H.: Tracing ray differentials. In: Proceedings of the 26th Annual Conference on Computer Graphics and Interactive Techniques, SIGGRAPH ’99, pp. 179–186. ACM Press/Addison-Wesley Publishing Co., New York (1999)
Jakob, W., Hašan, M., Yan, L.Q., Lawrence, J., Ramamoorthi, R., Marschner, S.: Discrete stochastic microfacet models. ACM Trans. Graph. 33(4), 115:1–115:10 (2014)
Lewis, R.R.: Making shaders more physically plausible. Comput. Graph. Forum 13(2), 109–120 (1994)
Merillou, S., Dischler, J., Ghazanfarpour, D.: Surface scratches: measuring, modeling and rendering. Vis. Comput. 17(1), 30–45 (2001)
Olano, M., Baker, D.: Lean mapping. In: Proceedings of the 2010 ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, I3D ’10, pp. 181–188. ACM, New York (2010)
Pharr, M., Jakob, W., Humphreys, G.: Physically Based Rendering: From Theory to Implementation, 3rd edn. Morgan Kaufmann Publishers Inc., San Francisco (2016)
Raymond, B., Guennebaud, G., Barla, P.: Multi-scale rendering of scratched materials using a structured SV-BRDF model. ACM Trans. Graph. 35(4), 57:1–57:11 (2016)
Smith, B.: Geometrical shadowing of a random rough surface. IEEE Trans. Antennas Propag. 15(5), 668–671 (1967)
Suykens, F., Willems, Y.D.: Path differentials and applications. In: Gortler, S.J., Myszkowski, K. (eds.) Rendering Techniques 2001, pp. 257–268. Springer, Vienna (2001)
Toksvig, M.: Mipmapping normal maps. J. Graph. Tools 10(3), 65–71 (2005)
Walter, B., Marschner, S.R., Li, H., Torrance, K.E.: Microfacet models for refraction through rough surfaces. In: Proceedings of the 18th Eurographics Conference on Rendering Techniques, EGSR’07, pp. 195–206. Eurographics Association, Aire-la-Ville (2007)
Xu, C., Wang, R., Zhao, S., Bao, H.: Real-time linear BRDF MIP-mapping. Comput. Graph. Forum 36(4), 27–34 (2017)
Yan, L.Q., Hašan, M., Jakob, W., Lawrence, J., Marschner, S., Ramamoorthi, R.: Rendering glints on high-resolution normal-mapped specular surfaces. ACM Trans. Graph. 33(4), 116:1–116:9 (2014)
Yan, L.Q., Hašan, M., Marschner, S., Ramamoorthi, R.: Position-normal distributions for efficient rendering of specular microstructure. ACM Trans. Graph. 35(4), 56:1–56:9 (2016)
Yan, L.Q., Hašan, M., Walter, B., Marschner, S., Ramamoorthi, R.: Rendering specular microgeometry with wave optics. ACM Trans. Graph. 37(4), 75:1–75:10 (2018)
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Chermain, X., Claux, F. & Mérillou, S. A microfacet-based BRDF for the accurate and efficient rendering of high-definition specular normal maps. Vis Comput 36, 267–277 (2020). https://doi.org/10.1007/s00371-018-1606-7
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DOI: https://doi.org/10.1007/s00371-018-1606-7