Following the remarkable success of diffusion models on image generation,
recent works have also demonstrated their impressive ability to address a
number of inverse problems in an unsupervised way, by properly constraining the
sampling process based on a conditioning input. Motivated by this, in this
paper, we present the first approach to use diffusion models as a prior for
highly accurate 3D facial BRDF reconstruction from a single image. We start by
leveraging a high-quality UV dataset of facial reflectance (diffuse and
specular albedo and normals), which we render under varying illumination
settings to simulate natural RGB textures and, then, train an unconditional
diffusion model on concatenated pairs of rendered textures and reflectance
components. At test time, we fit a 3D morphable model to the given image and
unwrap the face in a partial UV texture. By sampling from the diffusion model,
while retaining the observed texture part intact, the model inpaints not only
the self-occluded areas but also the unknown reflectance components, in a
single sequence of denoising steps. In contrast to existing methods, we
directly acquire the observed texture from the input image, thus, resulting in
more faithful and consistent reflectance estimation. Through a series of
qualitative and quantitative comparisons, we demonstrate superior performance
in both texture completion as well as reflectance reconstruction tasks.

该论文提出了第一种使用扩散模型作为先验的高精度三维面部 BRDF 重建方法，通过利用高质量的 UV 数据集进行渲染，使用样本处理过程来训练扩散模型，并在测试时通过对给定图像进行三维可塑模型拟合和 UV 纹理解耦，从而能够单个去噪步骤中完成掩蔽区域的纹理完成和未知反射组分的纹理自动填充，相较于现有方法，该方法更能忠实地和一致地估算反射率。

通过扩散模型从一张单照片中重光一个重光可调的 3D 人脸

Relightify: Relightable 3D Faces from a Single Image via Diffusion  Models

This study explores the use of photometric techniques (shape-from-shading and
uncalibrated photometric stereo) for upsampling the low-resolution depth map
from an RGB-D sensor to the higher resolution of the companion RGB image. A
single-shot variational approach is first put forward, which is effective as
long as the target's reflectance is piecewise-constant. It is then shown that
this dependency upon a specific reflectance model can be relaxed by focusing on
a specific class of objects (e.g., faces), and delegate reflectance estimation
to a deep neural network. A multi-shot strategy based on randomly varying
lighting conditions is eventually discussed. It requires no training or prior
on the reflectance, yet this comes at the price of a dedicated acquisition
setup. Both quantitative and qualitative evaluations illustrate the
effectiveness of the proposed methods on synthetic and real-world scenarios.

本研究探索了使用光度学技术（阴影形状和非标定光度立体）将 RGB-D 传感器的低分辨率深度图上采样到伴随的 RGB 图像的高分辨率。首先提出了一种有效的单次变分方法，而这依赖于目标的反射率是分段常数。随后，展示了这个依赖特定反射模型的限制可以通过关注特定类别的对象（例如面部），并将反射率估计委托给深度神经网络来缓解。最后讨论了一种基于随机变化光照条件的多次采集策略。这不需要反射率的培训或先前知识，但其代价是专用采集设置。通过定量和定性评估，证明了所提出方法在合成和真实场景中的有效性。