PCDiff新框架搞定3D点云弱缺陷检测，生成异常样本更逼真，重建更准，减少误报。
现有3D点云异常检测面临弱缺陷（如划痕）重建难，偏差仅10^{-3}，且背景非缺陷区易产生误报。PCDiff框架在生成阶段嵌入实例级多模态注意力，利用纹理梯度、图像块、文本和掩模条件生成高质量弱缺陷异常样本。检测阶段采用联合局部-全局重建算法，同时恢复局部异常和保持全局几何一致性。实验表明PCDiff在异常生成保真度和重建质量上显著超越现有方法。
Point Cloud Diffusion with Global and Local Reconstruction for Instance-Level 3D Anomaly Detection
3D anomaly detection in point clouds is critical for high-precision industrial manufacturing. Reconstruction-based methods have laid a strong foundation by detecting 3D anomalies through comparisons between defective inputs and their reconstructed normal counterparts. However, existing methods still suffer from two challenges: 1) the foreground weak defective regions such as scratches are hard to reconstruct and detect, where the anomaly deviations in normalized point clouds can be as small as $10^{-3}$; 2) the background non-defective regions are prone to get positional bias in reconstruction, which leads to false positives. To address these challenges, we propose \textbf{PCDiff}, a point cloud diffusion framework for instance-level 3D anomaly generation and detection. In the generation phase, an instance-level multi-modal attention is embedded into the generation framework, where anomalies are conditioned with texture gradient, image patch, text and mask. The instance-level condition enables the high-quality generation of weak-defective anomalies. In the detection phase, a joint local-global reconstruction algorithm is introduced to ensure local anomaly restoration and global geometric consistency, which preserves background normal structure while restoring the foreground defect. Extensive experiments demonstrate that the proposed PCDiff significantly outperforms state-of-the-art methods in both 3D anomaly generation fidelity and reconstruction quality, leading to substantial improvements in anomaly detection accuracy.