Research On Path Guiding Methods For Near-Specular Caustics Rendering

Caustics are a common optical phenomenon that typically manifests as high-frequency indirect illumination on rough surfaces.For photorealistic rendering in the field of computer graphics,caustics,as part of global illumination,play an important role in enhancing the realism of rendering results,especially when describing smooth objects such as water surfaces,glass,and jewelry.Therefore,in the research of photorealistic rendering,the problem of caustic rendering has been widely concerned.The difficulty of caustic rendering is that the caustic effect corresponds to high-intensity indirect lighting focused on a small area,and the rendering methods based on Monte Carlo sampling can hardly find the light propagation paths distributed in these small areas,resulting in poor rendering efficiency.Near-specular caustics are bright patterns or bright areas formed by rays of light reflecting or refracting off a smooth(non-perfect mirror)surface and concentrating on a rougher surface.Compared with caustics formed by perfect mirrors,near-specular caustics involve more complex light propagation and are less efficient to render.In the real world,perfect mirrors do not exist.There are only smooth surfaces close to perfect mirrors,so near-specular caustics are more realistic than perfect specular caustics.This paper conducts research on the near-specular caustic rendering problem,deeply analyzes the shortcomings of existing methods,and proposes a novel near-specular caustic rendering method.The existing near-specular caustic rendering methods can be summarized into bidirectional,path guiding,specular manifold,etc.These methods have achieved great improvements over the classic path tracing method,but there are still problems such as low rendering efficiency,inaccurate rendering results,and limited number of bounces,etc.This paper proposes a path-guiding method based on representative specular paths to solve the above problems.First,different from the classic Monte Carlo sampling method,this paper uses a numerical root-finding method to obtain representative light transport paths in the scene.Then.the indirect illumination distribution is estimated from these representative paths to guide the sampling process of path tracing.In this way,the efficiency of near-specular caustics rendering is improved while ensuring the accuracy of the results.The main contributions of this paper are as follows:1)This paper conducts extensive research on caustic rendering methods,analyzing the advantages and limitations of the existing methods.2)This paper proposes a path-guiding method based on representative specular paths,which can achieve high-efficiency rendering of near-specular caustics,ensure the accuracy of rendering results,and support multiple reflections.Compared with the existing path-guiding methods,the visual artifacts in the rendering results are significantly reduced,and the RMSE is lower.3)Sufficient experimental comparisons have been carried out to verify the superiority of the method in this paper when rendering near-specular caustics.