Despite much progress, achieving real-time high-fidelity head avatar animation is still difficult and existing methods have to trade-off between speed and quality. 3DMM based methods often fail to model non-facial structures such as eyeglasses and hairstyles, while neural implicit models suffer from deformation inflexibility and rendering inefficiency. Although 3D Gaussian has been demonstrated to possess promising capability for geometry representation and radiance field reconstruction, applying 3D Gaussian in head avatar creation remains a major challenge since it is difficult for 3D Gaussian to model the head shape variations caused by changing poses and expressions. In this paper, we introduce PSAvatar, a novel framework for animatable head avatar creation that utilizes discrete geometric primitive to create a parametric morphable shape model and employs 3D Gaussian for fine detail representation and high fidelity rendering. The parametric morphable shape model is a Point-based Morphable Shape Model (PMSM) which uses points instead of meshes for 3D representation to achieve enhanced representation flexibility. The PMSM first converts the FLAME mesh to points by sampling on the surfaces as well as off the meshes to enable the reconstruction of not only surface-like structures but also complex geometries such as eyeglasses and hairstyles. By aligning these points with the head shape in an analysis-by-synthesis manner, the PMSM makes it possible to utilize 3D Gaussian for fine detail representation and appearance modeling, thus enabling the creation of high-fidelity avatars. We show that PSAvatar can reconstruct high-fidelity head avatars of a variety of subjects and the avatars can be animated in real-time ($\ge$ 25 fps at a resolution of 512 $\times$ 512 ).

翻译：尽管取得了诸多进展，实现实时高保真头部虚拟人动画仍面临挑战，现有方法需在速度与质量间权衡。基于3DMM的方法常无法建模眼镜、发型等非面部结构，而神经隐式模型则存在变形灵活性不足与渲染效率低下问题。虽然三维高斯已被证明在几何表示与辐射场重建方面具有潜力，但将其应用于头部虚拟人创建仍面临重大挑战，因为三维高斯难以建模由姿态和表情变化引起的头部形状变化。本文提出PSAvatar——一种新型可动画化头部虚拟人创建框架，该框架利用离散几何基元构建参数化可变形形状模型，并采用三维高斯实现精细细节表示与高保真渲染。参数化可变形形状模型是一种基于点的可变形形状模型（PMSM），它以点而非网格进行三维表示，从而获得更强的表示灵活性。PMSM首先通过表面采样及网格外采样将FLAME网格转换为点，使其不仅能重建表面类结构，还能重建眼镜、发型等复杂几何体。通过以合成式分析方式将这些点与头部形状对齐，PMSM使得利用三维高斯进行精细细节表示与外观建模成为可能，从而创建高保真虚拟人。实验表明，PSAvatar可重建多种主体的高保真头部虚拟人，且这些虚拟人能实现实时动画（分辨率512×512时帧率≥25帧/秒）。