RealMat: Realistic Materials With Diffusion and Reinforcement Learning

Abstract Generative models for high‐quality materials are particularly desirable to make 3D content authoring more accessible. However, the majority of material generation methods are trained on synthetic data. Synthetic data provide precise supervision for material maps, which is convenient but also tends to create a significant visual gap with real‐world materials. Alternatively, recent work used a small dataset of real flash photographs to guarantee realism; however, such data are limited in scale and diversity. To address these limitations, we propose RealMat, a diffusion‐based material generator that leverages realistic priors, including a text‐to‐image model and a dataset of realistic material photos under natural lighting. In RealMat, we first fine‐tune a pre‐trained Stable Diffusion XL (SDXL) with synthetic material maps arranged in grids. This way, our model inherits some realism of SDXL while learning the data distribution of the synthetic material grids. Still, this creates a realism gap, with some generated materials appearing synthetic. We propose to further fine‐tune our model through reinforcement learning (RL), encouraging the generation of realistic materials. We develop a realism reward function for any material image under natural lighting, by collecting a large‐scale dataset of realistic material images. We show that this approach increases generated materials' realism compared to our base model and related work.