Rate-Rendering Distortion Optimized Preprocessing for Texture Map Compression of 3D Reconstructed Scenes

Textured meshes are widely used in computer graphics to represent 3D scenes, with UV mapping playing a crucial role in establishing a bijective mapping between the 3D mesh surface and a 2D texture. This mapping not only allows for the enhancement of rendering quality but also enables the compression of mesh textures using standard 2D image or video codecs. However, when reconstructing meshes from real-world multiview images, the resulting UV texture maps often suffer from fragmentation due to geometric inaccuracies and excessive tessellation of the reconstructed surfaces, leading to decreased compression performance. In this paper, we propose a novel and effective preprocessing approach for UV texture map compression based on rate-rendering distortion (R-RD) optimization. Unlike existing methods that rely on padding or smoothing, our method iteratively updates the texture map using the gradient of a joint cost of bitrate and rendering distortion. This cost is estimated through a differentiable image encoder and a differentiable texture sampling. Experimental results with lossless compressed mesh geometry demonstrate that our preprocessing method outperforms existing texture padding methods, achieving BD-rate reductions of at least 10.23%, 15.24%, and 12.10% when combined with JPEG, HEVC, and VVC, respectively. We also validate the effectiveness of our method with lossy compressed meshes using Google Draco, showing improved compression efficiency compared to the lossless geometry scenario. Subjective evaluations further confirm that our method enhances both color and structural continuities in the texture map by automatically eliminating high-frequency components unfavorable to compression. The paper provides comprehensive experiments and analyses, including rate estimation with different choices of differentiable image encoders, texture map distortion vs. rendering distortion, and complexity comparison with existing methods.