医学影像体渲染中实现精确半空间裁剪，提升细节保真度与实时性。
XClipGS: Exact Half-Space Clipping for Medical Volume Gaussian Splatting
- 基于仿射模型推导出可微分的闭式裁剪算子，无需额外参数或网络
- 在8个CT/MRI数据上平均PSNR达33.56dB，比基线高1.22dB，帧率超650FPS
- 裁剪面误差更小，泄漏量减少40倍，适合临床交互式可视化场景
高斯点云代理实现了医学体数据的交互式渲染，但裁剪平面会暴露未受外部视角训练约束的内部结构，并与传统点渲染中只能整体保留或丢弃的原始体素相交。本文提出XClipGS（eXact Clipping），将问题拆解为运行时裁剪操作与隐藏内部结构的监督两部分。在EWA高斯点采用的局部仿射模型下，半空间限制下的高斯射线积分可精确分解为二维投影和一个关于像素坐标的条件高斯累积分布函数。由此得到的逐像素闭式算子不引入学习参数或辅助网络，且对原始体素与平面均保持可微。通过多距离参考视图、不同裁剪轴与偏移量监督内部结构。提出配对裁剪/未裁剪切面协议，采用差值参考的切面误差（CDE）与剔除侧泄漏（Leak）指标，避免全局图像指标稀释近平面误差。在8个未用于训练的CT与MRI体数据上，XClipGS在所有数据上均取得最高PSNR（33.56 dB vs ClipGS的32.34 dB），渲染速度超过650 FPS，远超实时；在体轴切面下，平均带状SSIM从0.809提升至0.860，泄漏量减少约40倍。无需重训练即在任意法向平面下取得四项指标综合最优表现；固定内部结构下，达到RaRa的切面保真度，泄漏量减少约16倍。
原文摘要 · Abstract (English)
Gaussian-splatting proxies enable interactive rendering of volumetric medical scans, but a clipping plane exposes anatomy not constrained by external-view training and intersects primitives that conventional splatting can only keep or drop whole. We present XClipGS (eXact Clipping), which treats these as two separate problems: the render-time clip operator and supervision of the hidden interior. Under the local affine model used by EWA splatting, the ray integral of a half-space-restricted Gaussian factorizes exactly into its ordinary 2D footprint and a conditional Gaussian CDF whose argument is affine in pixel coordinates. The resulting closed-form per-pixel operator introduces no learned clipping parameters or auxiliary network and remains differentiable with respect to the primitive and plane. We use multi-distance reference views with varied clipping-plane axes and offsets to supervise the interior through the same operator. We also introduce a paired clipped/unclipped cut-face protocol with difference-referenced cut error (CDE) and culled-side leakage (Leak), because global image metrics dilute errors near the plane. On eight CT and MRI volumes with plane offsets not used for training, XClipGS attains the highest PSNR on every volume (33.56 versus 32.34 dB for ClipGS) while rendering at over 650 FPS, far above real time, versus 278 FPS. On voxel-axis cut-face views, it raises average band SSIM from 0.809 to 0.860 and leaks roughly 40 times less. Without retraining, it also achieves the best average across all four metrics on arbitrary-normal planes; on a fixed interior, it matches RaRa's face fidelity with about 16 times less leakage. Project page: https://gaozhongpai.github.io/XClipGS/
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