提出新方法实现高速高精度相位解包裹,适用于实时4D人脸扫描。
Hierarchical GraphCut Phase Unwrapping based on Invariance of Diffeomorphisms Framework
- 将图切割解包裹转化为像素标签问题,利用微分同胚不变性提升估计精度。
- 实验显示速度提升45.5倍,且L2误差更低,满足实时应用需求。
- 适合需要高动态3D重建的VR/AR、医疗成像等场景,尤其擅长复杂几何处理。
近年来,3D扫描技术快速发展,广泛应用于VR/AR、数字人创建和医学成像等领域。基于相移技术的结构光扫描因其使用低强度可见光且精度高,特别适合捕捉4D面部动态。核心步骤是相位解包裹,即从模2π的测量值中恢复连续相位Φ = φ + 2πk中的真实相位φ。目标是估计整数相位计数k。噪声、遮挡和复杂三维几何导致解包裹困难,因该问题本质病态:仅提供模2π信息,需依赖表面连续性假设来估计k。现有方法在速度与精度间权衡:快速方法精度不足,精确算法又难以实现实时处理。本文提出一种基于微分同胚不变性的分层图切割相位解包裹框架,将图切割解包裹重新建模为像素标签问题。通过共形和最优传输(OT)映射在图像空间中应用微分同胚不变性,预先计算奇数个微分同胚,再在每个域中采用分层图切割算法,最终通过多数投票融合标签图,鲁棒估计每个像素的k值。实验表明,真实实验与仿真均实现45.5倍速度提升且L2误差更低,具备实时应用潜力。
原文摘要 · Abstract (English)
Recent years have witnessed rapid advancements in 3D scanning technologies, with applications spanning VR/AR, digital human creation, and medical imaging. Structured-light scanning with phase-shifting techniques is preferred for its use of low-intensity visible light and high accuracy, making it well suited for capturing 4D facial dynamics. A key step is phase unwrapping, which recovers continuous phase values from measurements wrapped modulo 2pi. The goal is to estimate the unwrapped phase count k in the equation Phi = phi + 2pi k, where phi is the wrapped phase and Phi is the true phase. Noise, occlusions, and complex 3D geometry make recovering the true phase challenging because phase unwrapping is ill-posed: measurements only provide modulo 2pi values, and estimating k requires assumptions about surface continuity. Existing methods trade speed for accuracy: fast approaches lack precision, while accurate algorithms are too slow for real-time use. To overcome these limitations, this work proposes a phase unwrapping framework that reformulates GraphCut-based unwrapping as a pixel-labeling problem. This framework improves the estimation of the unwrapped phase count k through the invariance property of diffeomorphisms applied in image space via conformal and optimal transport (OT) maps. An odd number of diffeomorphisms are precomputed from the input phase data, and a hierarchical GraphCut algorithm is applied in each domain. The resulting label maps are fused via majority voting to robustly estimate k at each pixel. Experimental results demonstrate a 45.5x speedup and lower L2 error in real experiments and simulations, showing potential for real-time applications.
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