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曲面高精度次表面散射渲染方法

High Precision Subsurface Scattering Rendering Technique for Curved Surfaces

  • 摘要: 次表面散射光是确保半透明材料视觉效果的关键因素, 在电影游戏、虚拟现实中有重要的应用价值. 针对现有技术依赖平面漫反射剖面, 导致渲染复杂曲面时存在散射光颜色失真、阴影过渡生硬的问题, 提出一种基于多极子模型的预积分方法, 以提高曲面模型次表面散射精度. 首先使用多极子模型构建准确的曲面单层和多层漫反射剖面; 然后对漫反射剖面预先积分并将结果保存到查找表中, 通过增加单次散射进一步提高散射精度; 最后在实时渲染时结合贴图模糊技术, 提高平均曲率的准确性. 为了提高特定情况的散射效果, 讨论了透射光对散射效果的贡献. 针对人脸渲染的实验结果表明, 所提方法在SSIM, RMSE等各项误差指标中均优于现有预积分方法, 在保证渲染速度的同时能够消除之前的曲面散射误差, 有效地提高渲染真实感.

     

    Abstract: Subsurface scattering is a key factor in ensuring the visual effects of translucent materials, and it holds significant application value in film, gaming, virtual reality, and digital twin technology. However, existing technologies rely on planar diffusion profiles, which lead to issues such as color distortion and harsh shadow transitions when rendering complex surfaces. To address these issues, this paper proposes a pre-integration method based on multipole theory to enhance the accuracy of subsurface scattering on surface models. Initially, it employs the multipole model to build accurate single-layer and multi-layer diffusion profiles for surfaces. Subsequently, these diffusion profiles are pre-integrated into a Lookup Table (LUT), and single scattering is included to further improve the scattering precision. Lastly, during real-time rendering, texture blur techniques are used in conjunction with LUT to improve the accuracy of the average curvature. Moreover, the paper discusses the contribution of transmitted light to the scattering effect in order to enhance the scattering in specific scenarios. Experiments focused on facial rendering demonstrate that the proposed method outperforms existing pre-integration techniques in error metrics such as SSIM and RMSE, and effectively eliminates previous errors in surface scattering while maintaining rendering speed and significantly enhancing the realism of the render.

     

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