Artistic authoring of 3D environments is a laborious enterprise that also requires skilled content creators. There have been impressive improvements in using machine learning to address different aspects of generating 3D content, such as generating meshes, arranging geometry, synthesizing textures, etc. In this paper we develop a model to generate Bidirectional Reflectance Distribution Functions (BRDFs) from descriptive textual prompts. BRDFs are four dimensional probability distributions that characterize the interaction of light with surface materials. They are either represented parametrically, or by tabulating the probability density associated with every pair of incident and outgoing angles. The former lends itself to artistic editing while the latter is used when measuring the appearance of real materials. Numerous works have focused on hypothesizing BRDF models from images of materials. We learn a mapping from textual descriptions of materials to parametric BRDFs. Our model is first trained using a semi-supervised approach before being tuned via an unsupervised scheme. Although our model is general, in this paper we specifically generate parameters for MDL materials, conditioned on natural language descriptions, within NVIDIA's Omniverse platform. This enables use cases such as real-time text prompts to change materials of objects in 3D environments such as "dull plastic" or "shiny iron". Since the output of our model is a parametric BRDF, rather than an image of the material, it may be used to render materials using any shape under arbitrarily specified viewing and lighting conditions.

翻译：三维环境的艺术创作是一项劳动密集型工作，且需要熟练的内容创作者。近年来，利用机器学习解决三维内容生成不同方面（如生成网格、布局几何体、合成纹理等）已取得显著进展。本文开发了一种模型，能够从描述性文本提示生成双向反射分布函数（BRDF）。BRDF是描述光线与表面材料相互作用的四维概率分布，其表示方式有两种：参数化表示或通过表格记录每个入射角与出射角对应的概率密度。前者适用于艺术编辑，后者常用于测量真实材料的外观。已有大量研究聚焦于从材料图像中推断BRDF模型。本文学习从材料文本描述到参数化BRDF的映射。我们的模型首先采用半监督方法训练，随后通过无监督方案进行微调。尽管模型具有通用性，本文具体针对NVIDIA Omniverse平台，基于自然语言描述生成MDL材料的参数。这实现了实时文本提示改变三维环境中物体材质（如"哑光塑料"或"亮面铁")的应用场景。由于模型输出为参数化BRDF而非材料图像，可在任意指定的视角与光照条件下，使用任意形状对材料进行渲染。