We present the Minimal Retroreflective Microfacet (MRM) model, which turns any existing microfacet BSDF into a physically plausible retroreflective one by a single substitution: replacing the view direction with its reflection about the surface normal before evaluating the standard model. Based on the previously published back-vector formulation, MRM requires only minimal code changes and has been adopted in the OpenPBR and MaterialX material standards. We prove reciprocity and energy conservation under the assumption of a reflection-symmetric normal distribution function (NDF), which holds for all commonly used distributions, and validate the model against measured retroreflective material data.

翻译：我们提出了最小逆反射微面（MRM）模型，该模型通过一个简单的替换即可将任何现有的微面BSDF转变为物理合理的逆反射模型：在评估标准模型之前，将视线方向替换为其关于表面法线的反射方向。MRM基于先前发表的背向向量公式，仅需极少的代码修改，并已被纳入OpenPBR和MaterialX材质标准中。我们证明了在反射对称法线分布函数（NDF）假设下的互易性和能量守恒性，该假设适用于所有常用分布，并通过实测逆反射材料数据对模型进行了验证。