Recent advances in Neural Radiance Fields (NeRFs) have made it possible to reconstruct and reanimate dynamic portrait scenes with control over head-pose, facial expressions and viewing direction. However, training such models assumes photometric consistency over the deformed region e.g. the face must be evenly lit as it deforms with changing head-pose and facial expression. Such photometric consistency across frames of a video is hard to maintain, even in studio environments, thus making the created reanimatable neural portraits prone to artifacts during reanimation. In this work, we propose CoDyNeRF, a system that enables the creation of fully controllable 3D portraits in real-world capture conditions. CoDyNeRF learns to approximate illumination dependent effects via a dynamic appearance model in the canonical space that is conditioned on predicted surface normals and the facial expressions and head-pose deformations. The surface normals prediction is guided using 3DMM normals that act as a coarse prior for the normals of the human head, where direct prediction of normals is hard due to rigid and non-rigid deformations induced by head-pose and facial expression changes. Using only a smartphone-captured short video of a subject for training, we demonstrate the effectiveness of our method on free view synthesis of a portrait scene with explicit head pose and expression controls, and realistic lighting effects. The project page can be found here: http://shahrukhathar.github.io/2023/08/22/CoDyNeRF.html

CoDyNeRF是一个在现实世界的采集条件下创建完全可控的3D肖像的系统，通过在规范空间中基于预测的表面法线和面部表情与头部姿态变形的条件下近似光照相关效果的动态外观模型来学习，它使用3DMM法线作为人头粗略法线的先验之一来引导表面法线预测，只需要使用手机拍摄的短视频进行训练，我们展示了该方法在具有明确头部姿态和表情控制以及逼真光照效果的肖像场景的自由视图合成中的有效性。

可控的神经网络3D肖像的动态外貌