Additional Progress Towards the Unification of Microfacet and Microflake Theories



Jonathan Dupuy Eric Heitz Eugene d'Eon
Unity Technologies Unity Technologies 8i

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Follow-up on Heitz et al.

Single
Photo
Multiple

Problem



Surface $\overset{?}{\longrightarrow}$ Volume

Our approach: preserve light transport
using microfacet and microflake theories

Outline


What is responsible for surface light transport ?
A: microfacet NDF + geometric profile (e.g., Smith)
What is responsible for volume light transport ?
A: microflake NDF + microflake density
How to make a volume act as a surface ?
A: microfacet NDF + semi-infinite homogeneous density
Discussion

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Microfacet Surface

Microfacet Surface

Microfacet Surface


Definition

  • BSDF framework
  • BSDF = facets


Components

  • µBSDF
  • NDF

Outline


What is responsible for surface light transport ?
A: microfacet NDF
What is responsible for volume light transport ?
A: microflake NDF + microflake density
How to make a volume act as a surface ?
A: microfacet NDF + semi-infinite homogeneous density
Discussion

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Microflake Volume


Definition

  • medium framework
  • medium = flakes


Components

  • density
  • µBSDF
  • NDF

Outline


What is responsible for surface light transport ?
A: microfacet NDF
What is responsible for volume light transport ?
A: microflake NDF + microflake density
How to make a volume act as a surface ?
A: microfacet NDF + semi-infinite homogeneous density
Discussion

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Outline


What is responsible for surface light transport ?
A: microfacet NDF
What is responsible for volume light transport ?
A: microflake NDF + microflake density
How to make a volume act as a surface ?
A: microfacet NDF + semi-infinite homogeneous density
Discussion

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

$\Rightarrow$ How to support both types of microflakes inside a single medium ?

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Chandrasekhar $$\boxed{f_r = \frac{a}{4\pi} \frac{H(\cos \theta_i) \, H(\cos \theta_o)}{\cos \theta_i + \cos \theta_o}}$$

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Chandrasekhar $$\boxed{f_r = \frac{a}{4\pi} \frac{H(\cos \theta_i) \, H(\cos \theta_o)}{\cos \theta_i + \cos \theta_o}}$$
$\Rightarrow$ Can we generalize to other NDFs ?

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Semiporous Materials

Semiporous Materials

Semiporous Materials

Semiporous Materials

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail
close
1 voxel/pixel
2000MB
far
8 voxels/pixel
2000MB
far
1 voxel/pixel
16MB

Discussion


Topics

  • unified theory
  • multiscattering BSDFs
  • closed-form LT
  • semiporous materials
  • level-of-detail
close
1 voxel/pixel
2000MB
far
8 voxels/pixel
2000MB
far
1 voxel/pixel
16MB

Questions







Backup Slides

Surface-Like Microflake Volume


Geometry

  • semi-infinite
  • homogeneous
  • exponential free paths
  • microfacet NDF


Properties

  • monosided flakes
  • surface-like LT

Multiple Scattering Microfacet BSDF