Non-Photorealistic Rendering for 3D Digitalization of Chinese Painting: Technique–Algorithm Matrix and Case Study of Qian Xuan’s Eight Flowers

Traditional Chinese painting is an essential component of cultural heritage, and its 3D digitalization plays a crucial role in cultural dissemination and artistic reproduction. However, existing Non-Photorealistic Rendering (NPR) approaches face limitations in reproducing Chinese paintings, such as loss of artistic spirit, unclear workflows, and high learning costs for creators. To address these issues, this study introduces a “Chinese Painting Technique–NPR Algorithm Matching Matrix,” which quantitatively maps five major categories of traditional techniques to 24 mainstream NPR algorithms, providing systematic guidelines for algorithm selection. Based on this framework, we develop a layered collaborative 3D digitalization pipeline, exemplified through Qian Xuan’s Eight Flowers , and incorporate an Artist-in-the-loop mechanism to ensure artistic fidelity. Furthermore, a multidimensional evaluation system was established, combining general metrics (LPIPS, SSIM) with newly designed indicators for color fidelity, brushstroke texture, surface texture, and glossiness, alongside subjective evaluation via blind tests. The results demonstrate that our method achieves a favorable balance between artistic authenticity and computational efficiency, outperforming existing projects in both objective scores and perceptual realism. This research not only provides a new pathway for the digital preservation and dissemination of Chinese paintings but also extends the application potential of NPR techniques in cultural heritage.