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Remove provision for specular_weight to exceed 1 #228

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Remove provision for specular_weight to exceed 1 #228

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4f847f2
Remove provision for specular_weight to exceed 1
portsmouth Jul 31, 2024
aee8093
Remove unnecessary clamp in MaterialX graph
portsmouth Sep 17, 2024
8481044
Merge branch 'dev_1.2' into specular_weight_fix
portsmouth Sep 18, 2024
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5 changes: 1 addition & 4 deletions index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -507,12 +507,9 @@
\end{equation}
Applying this modulated IOR ratio $\eta^\prime_s$ in the angle-dependent dielectric Fresnel formula $F(\mu, \eta^\prime_s)$ then produces the desired reflectivity modulation at any incident angle cosine $\mu$. The Fresnel transmission factor and refraction into and out of the base dielectric should also be consistent with the IOR ratio $\eta^\prime_s$.

For convenience, we also allow $\xi_s = \mathtt{specular\_weight}$ to exceed 1 so that the reflectivity is increased above the level set by **`specular_ior`**. Note though there is a constraint $\xi_s \le 1/F_s$ since the scaled reflection coefficient cannot exceed $1$. So there needs to be an internal clamp to ensure $\xi_s \in [0, 1/F_s]$.


Specular params | Label | Type | Range | Norm | Default | Description
------------------------------------|------------|----------|:---------------:|:----------:|:-------------:|----------------------------------------------
**`specular_weight`** | Weight | `float` | $ [0, \infty) $ | $ [0, 1] $ | $ 1 $ | Modulates the dielectric reflectivity at normal incidence
**`specular_weight`** | Weight | `float` | $ [0, 1] $ | | $ 1 $ | Modulates the dielectric reflectivity at normal incidence
**`specular_color`** | Color | `color3` | $ [0, 1]^3 $ | | $ (1, 1, 1) $ | Tints the dielectric Fresnel factor
**`specular_roughness`** | Roughness | `float` | $ [0, 1] $ | | $ 0.3 $ | Roughness of NDF of dielectric BSDF $f_\mathrm{dielectric}$
**`specular_roughness_anisotropy`** | Anisotropy | `float` | $ [0, 1] $ | | $ 0 $ | Anisotropy of NDF of dielectric BSDF $f_\mathrm{dielectric}$
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7 changes: 1 addition & 6 deletions reference/open_pbr_surface.mtlx
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Expand Up @@ -341,13 +341,8 @@
<input name="in1" type="float" interfacename="specular_weight" />
<input name="in2" type="float" nodename="specular_F0" />
</multiply>
<clamp name="scaled_specular_F0_clamped" type="float">
<input name="in" type="float" nodename="scaled_specular_F0" />
<input name="low" type="float" value="0.0" />
<input name="high" type="float" value="0.99999" />
</clamp>
<sqrt name="sqrt_scaled_specular_F0" type="float">
<input name="in" type="float" nodename="scaled_specular_F0_clamped" />
<input name="in" type="float" nodename="scaled_specular_F0" />
</sqrt>
<sign name="sign_eta_s_minus_one" type="float">
<input name="in" type="float" nodename="eta_s_minus_one" />
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