Multiple-Scattering Microfacet BSDFs with the Smith Model

TL;DR

Multiple scattering of light on rough materials is a challenging problem in computer graphics, but a new model presented in this paper offers a practical solution.

Transcript

in this paper we address an important open problem in material modeling what happens when light scatters multiple times on rough material surfaces in image synthesis accurately describing light matter interactions is important for materials to obtain a realistic look however the multiple light matter interactions that we can see in this figure are ... Read More

Key Insights

• 💻 Accurately modeling multiple scattering on rough materials is a challenging problem in computer graphics.
• 🦠 The Smith micro surface model can be extended to incorporate multiple scattering by treating it as a volume scattering problem.
• 🙂 The model accurately predicts the albedo and angular distribution of light, even for various material properties and roughness levels.
• 👶 The new model avoids the darkening effects and produces interesting emerging effects, such as color saturation, on rough materials.
• 🥠 The model is robust and does not require parameter tuning for different roughness values.
• 🤑 It supports textured input, allowing for visually rich images.
• 🙌 Validation of the model shows its accuracy compared to ray tracing simulations with known material properties.

Questions & Answers

Q: What is the main issue with current surface appearance models for rough materials?

Current models neglect multiple light-matter interactions, causing a noticeable darkening of the material's appearance and energy loss.

Q: How does the new model address the problem of multiple scattering on rough materials?

The new model transforms the surface scattering problem into a volume scattering problem, using the Smith micro surface model as a starting point and incorporating higher-order scattering.

Q: Is the new model mathematically correct?

Yes, the model is mathematically correct and has been validated by comparing its predictions to ray tracing simulations with known material and statistics.

Q: Can the new model be practically implemented?

Yes, the model can be implemented as a classic psdf plugin and supports textured input, making it usable in physically-based renderers.

Summary & Key Takeaways

• Many surface appearance models do not accurately account for multiple light-matter interactions on rough material surfaces, leading to unrealistic rendering.

• The Smith micro surface model, commonly used for single scattering, can be extended to incorporate multiple scattering by transforming the surface scattering problem into a volume scattering problem.

• The new model accurately predicts the albedo and angular distribution of light for various materials, roughness levels, anisotropy, and inclinations.