Skip to content

Commit

Permalink
Rename base_roughness to base_diffuse_roughness (#175)
Browse files Browse the repository at this point in the history 
* Rename base_roughness to base_diffuse_roughness

* Update MaterialX file

* Update index.html
  • Loading branch information
@virtualzavie
virtualzavie authored Apr 25, 2024
1 parent 10695cc commit c7af677
Show file tree
Hide file tree
Showing 3 changed files with 11 additions and 11 deletions.
14 changes: 7 additions & 7 deletions index.html
View file
Original file line number Diff line number Diff line change
Expand Up @@ -571,7 +571,7 @@
\mathbf{E}_\textrm{glossy-diffuse} = \mathbf{E}_\textrm{spec} + \mathbf{E}_\textrm{diffuse}
\end{eqnarray}
where $\mathbf{E}_\mathrm{spec}$ is the normal-direction reflectance of all energy reflected from the dielectric interface without transmission, and $\mathbf{E}_\mathrm{diffuse}$ is the normal-direction reflectance of all energy transmitted through the interface, scattered off the diffuse medium, and transmitted back out.
We then _define_ $\mathbf{C} =$ **`base_weight`** * **`base_color`** to be such that the reflectance of the remaining energy transmitted into the slab, $\mathbf{E}_\textrm{diffuse}$ in the *zero* **`base_roughness`** case (i.e. a Lambertian base), is given by
We then _define_ $\mathbf{C} =$ **`base_weight`** * **`base_color`** to be such that the reflectance of the remaining energy transmitted into the slab, $\mathbf{E}_\textrm{diffuse}$ in the *zero* **`base_diffuse_roughness`** case (i.e. a Lambertian base), is given by
\begin{eqnarray} \label{glossy_diffuse_albedo_constraint}
\mathbf{E}_\textrm{diffuse} = \bigl( 1 - \mathbf{E}_\textrm{spec} \bigr) \mathbf{C} \ .
\end{eqnarray}
Expand All @@ -590,11 +590,11 @@
where $\mathcal{N}$ is a normalization factor such that equation [glossy_diffuse_albedo_constraint] is satisfied. In the case of a zero roughness (i.e. Lambertian) Oren-Nayar base $\mathcal{N}$ can be tabulated in terms of the dielectric IOR and roughness ([#Kutz2021]), and the required albedo of the Lambertian base is equal to $\mathbf{C}$ as in the non-reciprocal albedo-scaling approximation. Extending this to the more general case of a non-Lambertian rough Oren-Nayar base would require adding the roughness dimension to the tabulation, and the required Oren-Nayar albedo will not simply equal $\mathbf{C}$. We leave the specific choice of model and these details to the implementation.


Glossy-diffuse params | Label | Type | Range | Default | Description
----------------------|-----------|----------|:----------------:|:-------------------:|----------------------------------------------
**`base_weight`** | Weight | `float` | $ [0, 1] $ | $ 1 $ | Scalar multiplier to **`base_color`**
**`base_color`** | Color | `color3` | $ [0, 1]^3 $ | $ (0.8, 0.8, 0.8) $ | Base reflection albedo color according to equation [glossy_diffuse_albedo_constraint].
**`base_roughness`** | Roughness | `float` | $ [0, 1] $ | $ 0 $ | Roughness of the diffuse lobe $f_\mathrm{diffuse}$
Glossy-diffuse params | Label | Type | Range | Default | Description
-----------------------------|-------------------|----------|:----------------:|:-------------------:|----------------------------------------------
**`base_weight`** | Weight | `float` | $ [0, 1] $ | $ 1 $ | Scalar multiplier to **`base_color`**
**`base_color`** | Color | `color3` | $ [0, 1]^3 $ | $ (0.8, 0.8, 0.8) $ | Base reflection albedo color according to equation [glossy_diffuse_albedo_constraint].
**`base_diffuse_roughness`** | Diffuse Roughness | `float` | $ [0, 1] $ | $ 0 $ | Roughness of the diffuse lobe $f_\mathrm{diffuse}$


![](images/glossy_diffuse_diffuseonly.png width=99%) ![](images/glossy_diffuse_speconly.png width=99%) ![](images/glossy_diffuse_sum.png width=99%)
Expand Down Expand Up @@ -1077,7 +1077,7 @@
E_R[f^R_\mathrm{diffuse}] + E_T[f^T_\mathrm{diffuse}] = S \le 1 \ .
\end{equation}
At the default of zero anisotropy ($g=0$) the energy is balanced equally between diffuse reflection and transmission.
The diffuse transmission lobe shape (in both hemispheres) is assumed to be controlled by the **`base_roughness`** parameter. Typically the diffuse lobes $f_+$, $f_-$ will be represented by an Oren-Nayar lobe flipped into the appropriate hemisphere (which technically should be modified due to the dielectric boundaries, though a renderer may choose to ignore this). This model is useful for rendering cases such as light scattering through a thin sheet of paper (Figure [thinwalled]).
The diffuse transmission lobe shape (in both hemispheres) is assumed to be controlled by the **`base_diffuse_roughness`** parameter. Typically the diffuse lobes $f_+$, $f_-$ will be represented by an Oren-Nayar lobe flipped into the appropriate hemisphere (which technically should be modified due to the dielectric boundaries, though a renderer may choose to ignore this). This model is useful for rendering cases such as light scattering through a thin sheet of paper (Figure [thinwalled]).


![](images/thin_walled1.jpg width=99% align=right) ![](images/thin_walled2.jpg width=99% align=left)
Expand Down
2 changes: 1 addition & 1 deletion parametrization.md.html
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@
| **Base** |
| `base_weight` | Weight | `float` | $ [0, 1] $ | | $ 1 $ | |
| `base_color` | Color | `color3` | $ [0, 1]^3 $ | | $ (0.8, 0.8, 0.8) $ | |
| `base_roughness` | Roughness | `float` | $ [0, 1] $ | | $ 0 $ | |
| `base_diffuse_roughness` | Diffuse Roughness | `float` | $ [0, 1] $ | | $ 0 $ | |
| `base_metalness` | Metalness | `float` | $ [0, 1] $ | | $ 0 $ | |
| **Specular** |
| `specular_weight` | Weight | `float` | $ [0, 1] $ | | $ 1 $ | |
Expand Down
6 changes: 3 additions & 3 deletions reference/open_pbr_surface.mtlx
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@
doc="Multiplier on the intensity of the reflection from the diffuse and metallic base." />
<input name="base_color" type="color3" value="0.8, 0.8, 0.8" uimin="0,0,0" uimax="1,1,1" uiname="Base Color" uifolder="Base"
doc="Color of the reflection from the diffuse and metallic base." />
<input name="base_roughness" type="float" value="0.0" uimin="0.0" uimax="1.0" uiname="Base Roughness" uifolder="Base" uiadvanced="true"
<input name="base_diffuse_roughness" type="float" value="0.0" uimin="0.0" uimax="1.0" uiname="Base Diffuse Roughness" uifolder="Base" uiadvanced="true"
doc="Roughness of the diffuse reflection. Higher values cause the surface to appear flatter." />
<input name="base_metalness" type="float" value="0.0" uimin="0.0" uimax="1.0" uiname="Base Metalness" uifolder="Base"
doc="Specifies how metallic the base material appears (dials the base from pure dielectric to pure metal)." />
Expand Down Expand Up @@ -178,7 +178,7 @@
<oren_nayar_diffuse_bsdf name="subsurface_thin_walled_reflection_bsdf" type="BSDF">
<input name="weight" type="float" value="1.0" />
<input name="color" type="color3" nodename="subsurface_color_nonnegative" />
<input name="roughness" type="float" interfacename="base_roughness" />
<input name="roughness" type="float" interfacename="base_diffuse_roughness" />
<input name="normal" type="vector3" interfacename="geometry_normal" />
</oren_nayar_diffuse_bsdf>
<subtract name="one_minus_subsurface_anisotropy" type="float">
Expand Down Expand Up @@ -240,7 +240,7 @@
<oren_nayar_diffuse_bsdf name="diffuse_bsdf" type="BSDF">
<input name="weight" type="float" interfacename="base_weight" />
<input name="color" type="color3" nodename="base_color_nonnegative" />
<input name="roughness" type="float" interfacename="base_roughness" />
<input name="roughness" type="float" interfacename="base_diffuse_roughness" />
<input name="normal" type="vector3" interfacename="geometry_normal" />
</oren_nayar_diffuse_bsdf>
<convert name="subsurface_selector" type="float">
Expand Down

0 comments on commit c7af677

Please sign in to comment.