Recently, 3D Gaussian Splatting (3DGS) has achieved impressive results in novel view synthesis, demonstrating high fidelity and efficiency. However, it easily exhibits needle-like artifacts, especially when increasing the sampling rate. Mip-Splatting tries to remove these artifacts with a 3D smoothing filter for frequency constraints and a 2D Mip filter for approximated supersampling. Unfortunately, it tends to produce over-blurred results, and sometimes needle-like Gaussians still persist. Our spectral analysis of the covariance matrix during optimization and densification reveals that current 3DGS lacks shape awareness, relying instead on spectral radius and view positional gradients to determine splitting. As a result, needle-like Gaussians with small positional gradients and low spectral entropy fail to split and overfit high-frequency details. Furthermore, both the filters used in 3DGS and Mip-Splatting reduce the spectral entropy and increase the condition number during zooming in to synthesize novel view, causing view inconsistencies and more pronounced artifacts. Our Spectral-GS, based on spectral analysis, introduces 3D shape-aware splitting and 2D view-consistent filtering strategies, effectively addressing these issues, enhancing 3DGS's capability to represent high-frequency details without noticeable artifacts, and achieving high-quality realistic rendering.

The images are ordered from left to right, corresponding to the transition from the training focal length to larger focal lengths (zoom in). These methods produce nearly identical novel view synthesis results at the training view’s focal length. However, when the focal length and sampling rate increase, 3DGS and Mip-Splatting suffer from severe needle-like artifacts, leading to a notable decline in rendering quality.