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化身动画仍然困难重重，现有方法不得不在速度与质量之间进行权衡。基于3DMM的方法常难以建模非面部结构（如眼镜和发型），而神经隐式模型则面临变形灵活性不足和渲染效率低下的问题。尽管3D高斯已被证明在几何表示和辐射场重建方面具有潜力，但在头部虚拟化身创建中应用3D高斯仍是一项重大挑战，因为3D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，一种新颖的可动画头部虚拟化身创建框架，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3D高斯进行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），它使用点而非网格进行3D表示，以实现更强的表示灵活性。PMSM首先通过曲面采样及网格外采样将FLAME网格转换为点，从而不仅能够重建类曲面结构，还能重建眼镜、发型等复杂几何体。通过以分析合成方式将这些点与头部形状对齐，PMSM使得利用3D高斯进行精细细节表示和外观建模成为可能，进而实现高保真虚拟化身的创建。实验表明，PSAvatar能够重建多种对象的高保真头部虚拟化身，并且这些化身可实时动画化（在512 × 512分辨率下帧率≥25 fps）。