Refraction Rendering with Spectral Interval Sampling

The Monte Carlo rendering method requires sampling an additional spectral domain to produce advanced light phenomena like chromatic dispersion. However, this extension can lead to chromatic noise and slow convergence, which can be partially addressed through proper sample distribution. In this paper, we introduce a multiple wavelength sampling method that focuses on refractive dispersion effects for a single path. By combining the idea of line sampling used in direct illumination with the specular chain's property, we find a continuous solution space that we call the spectral interval. We then perform an analytical integration for incoming spectral radiance within this interval. This allows us to achieve low variance and reduced noise at a lower cost compared to naive sampling methods. Finally, our method can be integrated into existing Monte Carlo methods built within path space.