# SpongeCake: A Layered Microflake Surface Appearance Model

arXiv: https://arxiv.org/abs/2110.07145 · HTML: https://mlsanity.com/paper/2110.07145/

## Key facts

- Cited by 5 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 14 Oct 2021.

## Built on by (most cited first, 5 of 5)

- [ePBR: Extended PBR Materials in Image Synthesis](https://mlsanity.com/paper/2504.17062/) (2025)
- [UniVidX: A Unified Multimodal Framework for Versatile Video Generation via Diffusion Priors](https://mlsanity.com/paper/2605.00658/) (2026)
- [Woven Fabric Capture with a Reflection-Transmission Photo Pair](https://mlsanity.com/paper/2406.19398/) (2024)
- [Real-time Neural Woven Fabric Rendering](https://mlsanity.com/paper/2406.17782/) (2024)
- [FabricGen: Microstructure-Aware Woven Fabric Generation](https://mlsanity.com/paper/2603.07240/) (2026)

## Abstract (arXiv)

In this paper, we propose SpongeCake: a layered BSDF model where each layer is a volumetric scattering medium, defined using microflake or other phase functions. We omit any reflecting and refracting interfaces between the layers. The first advantage of this formulation is that an exact and analytic solution for single scattering, regardless of the number of volumetric layers, can be derived. We propose to approximate multiple scattering by an additional single-scattering lobe with modified parameters and a Lambertian lobe. We use a parameter mapping neural network to find the parameters of the newly added lobes to closely approximate the multiple scattering effect. Despite the absence of layer interfaces, we demonstrate that many common material effects can be achieved with layers of SGGX microflake and other volumes with appropriate parameters. A normal mapping effect can also be achieved through mapping of microflake orientations, which avoids artifacts common in standard normal maps. Thanks to the analytical formulation, our model is very fast to evaluate and sample. Through various parameter settings, our model is able to handle many types of materials, like plastics, wood, cloth, etc., opening a number of practical applications.