UV Lightmap Compression – MagicDawn Research

Lightmap Compression with Color-Coherent UV Clustering and Cascade Texture Optimization

Dehan Chen, Hongyu Huang, Yuzhe Luo, Hao Xu, Yuqing Zhang, Sipeng Yang, Xifeng Gao, Heng Cai, Chao Li, Xiaogang Jin

Eurographics 2026

Bedroom scene comparison with compressed lightmaps

Bedroom scene rendered with our compressed lightmaps (left) vs. ground-truth (right). Our method achieves an 83% reduction in storage cost with negligible perceptual differences (PSNR 51.79 dB, 1–SSIM 0.0027).

Abstract

To address the storage overhead of lightmaps and the limitations of existing compression techniques, we propose a novel UV-space compression framework based on per-triangle processing. By mapping triangles to a standardized domain, we cluster and repack color-coherent regions into a compact atlas, generating a cascade texture refined via differentiable rendering. Experimental results show an average storage reduction of 83% with approximately 10 dB higher PSNR than existing methods. Our approach is the first dedicated lightmap compression framework compatible with standard block-based formats, offering an effective solution for memory-efficient 3D asset delivery.

Method

Pipeline overview. Our three-stage framework: (a) Feature texture construction maps each UV triangle to a canonical square domain for robust similarity assessment. (b) Greedy graph partitioning clusters color-coherent triangles for UV repacking. (c) Cascade texture optimization via differentiable rendering produces compact dual-texture output.

Results

Visual results. For each mesh we show the original rasterized HDR radiance (left), our compressed result (middle), and amplified difference (right). Metrics (PSNR / 1-SSIM / CR) are averaged over all viewing directions.

Qualitative comparison. Our method produces smoother shadow boundaries without blocky artifacts from downsampling, and avoids color bleeding artifacts from prior UV-based approaches.