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Initial implementation of specular haze #298

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Initial implementation of specular haze #298

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113 changes: 111 additions & 2 deletions reference/open_pbr_surface.mtlx
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,10 @@
doc="Index of refraction of the dielectric base." />
<input name="specular_roughness_anisotropy" type="float" value="0.0" uimin="0.0" uimax="1.0" uiname="Specular Anisotropy" uifolder="Specular" uiadvanced="true"
doc="The directional bias of the roughness of the metal/dielectric base, resulting in increasingly stretched highlights along the tangent direction." />
<input name="specular_haze" type="float" value="0.0" uimin="0.0" uimax="1.0" uiname="Specular Haze" uifolder="Specular" uiadvanced="true"
doc="Mix weight of a secondary specular lobe for a hazy gloss appearance." />
<input name="specular_haze_spread" type="float" value="0.3" uimin="0.0" uimax="1.0" uiname="Specular Haze Spread" uifolder="Specular" uiadvanced="true"
doc="Extra roughness of the secondary haze lobe, interpolating between core roughness and 1." />
<input name="transmission_weight" type="float" value="0.0" uimin="0.0" uimax="1.0" uiname="Transmission Weight" uifolder="Transmission" uiadvanced="true" hint="transparency"
doc="Mixture weight between the transparent and opaque dielectric base. The greater the value the more transparent the material." />
<input name="transmission_color" type="color3" value="1, 1, 1" uimin="0,0,0" uimax="1,1,1" uiname="Transmission Color" uifolder="Transmission" uiadvanced="true"
Expand Down Expand Up @@ -141,6 +145,16 @@
<input name="low" type="float" value="0.0" />
<input name="high" type="float" value="1.0" />
</clamp>
<clamp name="specular_haze_clamped" type="float">
<input name="in" type="float" interfacename="specular_haze" />
<input name="low" type="float" value="0.0" />
<input name="high" type="float" value="1.0" />
</clamp>
<clamp name="specular_haze_spread_clamped" type="float">
<input name="in" type="float" interfacename="specular_haze_spread" />
<input name="low" type="float" value="0.0" />
<input name="high" type="float" value="1.0" />
</clamp>
<clamp name="transmission_weight_clamped" type="float">
<input name="in" type="float" interfacename="transmission_weight" />
<input name="low" type="float" value="0.0" />
Expand Down Expand Up @@ -303,6 +317,40 @@
<input name="anisotropy" type="float" nodename="specular_roughness_anisotropy_clamped" />
</open_pbr_anisotropy>

<!-- Calculate haze specular roughness -->
<!-- r_haze = lerp(specular_roughness, 1.0, specular_haze_spread) -->
<mix name="haze_roughness_base" type="float">
<input name="fg" type="float" value="1.0" />
<input name="bg" type="float" nodename="specular_roughness_clamped" />
<input name="mix" type="float" nodename="specular_haze_spread_clamped" />
</mix>
<!-- Apply coat roughening to haze roughness -->
<power name="haze_roughness_to_power_4" type="float">
<input name="in1" type="float" nodename="haze_roughness_base" />
<input name="in2" type="float" value="4.0" />
</power>
<add name="add_coat_and_haze_roughnesses_to_power_4" type="float">
<input name="in1" type="float" nodename="two_times_coat_roughness_to_power_4" />
<input name="in2" type="float" nodename="haze_roughness_to_power_4" />
</add>
<min name="min_1_add_coat_and_haze_roughnesses_to_power_4" type="float">
<input name="in1" type="float" value="1.0" />
<input name="in2" type="float" nodename="add_coat_and_haze_roughnesses_to_power_4" />
</min>
<power name="coat_affected_haze_roughness" type="float">
<input name="in1" type="float" nodename="min_1_add_coat_and_haze_roughnesses_to_power_4" />
<input name="in2" type="float" value="0.25" />
</power>
<mix name="effective_haze_roughness" type="float">
<input name="fg" type="float" nodename="coat_affected_haze_roughness" />
<input name="bg" type="float" nodename="haze_roughness_base" />
<input name="mix" type="float" nodename="coat_weight_clamped" />
</mix>
<open_pbr_anisotropy name="haze_roughness" type="vector2">
<input name="roughness" type="float" nodename="effective_haze_roughness" />
<input name="anisotropy" type="float" nodename="specular_roughness_anisotropy_clamped" />
</open_pbr_anisotropy>

<!-- Subsurface (thin-walled) -->
<oren_nayar_diffuse_bsdf name="subsurface_thin_walled_reflection_bsdf" type="BSDF">
<input name="color" type="color3" nodename="subsurface_color_clamped" />
Expand Down Expand Up @@ -528,8 +576,38 @@
<input name="bg" type="BSDF" nodename="dielectric_reflection" />
<input name="mix" type="float" nodename="thin_film_weight_clamped" />
</mix>

<!-- Dielectric Haze -->
<dielectric_bsdf name="dielectric_reflection_haze" type="BSDF">
<input name="tint" type="color3" nodename="specular_color_clamped" />
<input name="ior" type="float" nodename="modulated_eta_s" />
<input name="roughness" type="vector2" nodename="haze_roughness" />
<input name="normal" type="vector3" interfacename="geometry_normal" />
<input name="tangent" type="vector3" interfacename="geometry_tangent" />
<input name="scatter_mode" type="string" value="R" />
</dielectric_bsdf>
<dielectric_bsdf name="dielectric_reflection_haze_tf" type="BSDF">
<input name="tint" type="color3" nodename="specular_color_clamped" />
<input name="ior" type="float" nodename="modulated_eta_s" />
<input name="roughness" type="vector2" nodename="haze_roughness" />
<input name="normal" type="vector3" interfacename="geometry_normal" />
<input name="tangent" type="vector3" interfacename="geometry_tangent" />
<input name="scatter_mode" type="string" value="R" />
<input name="thinfilm_thickness" type="float" nodename="thin_film_thickness_nm" />
<input name="thinfilm_ior" type="float" nodename="thin_film_ior_nonnegative" />
</dielectric_bsdf>
<mix name="dielectric_reflection_haze_tf_mix" type="BSDF">
<input name="fg" type="BSDF" nodename="dielectric_reflection_haze_tf" />
<input name="bg" type="BSDF" nodename="dielectric_reflection_haze" />
<input name="mix" type="float" nodename="thin_film_weight_clamped" />
</mix>
<mix name="dielectric_reflection_with_haze" type="BSDF">
<input name="fg" type="BSDF" nodename="dielectric_reflection_haze_tf_mix" />
<input name="bg" type="BSDF" nodename="dielectric_reflection_tf_mix" />
<input name="mix" type="float" nodename="specular_haze_clamped" />
</mix>
<layer name="dielectric_base" type="BSDF">
<input name="top" type="BSDF" nodename="dielectric_reflection_tf_mix" />
<input name="top" type="BSDF" nodename="dielectric_reflection_with_haze" />
<input name="base" type="BSDF" nodename="dielectric_substrate" />
</layer>

Expand Down Expand Up @@ -561,8 +639,39 @@
<input name="bg" type="BSDF" nodename="metal_bsdf" />
<input name="mix" type="float" nodename="thin_film_weight_clamped" />
</mix>

<!-- Metal Haze -->
<generalized_schlick_bsdf name="metal_bsdf_haze" type="BSDF">
<input name="weight" type="float" nodename="specular_weight_nonnegative" />
<input name="color0" type="color3" nodename="metal_reflectivity" />
<input name="color82" type="color3" nodename="specular_color_clamped" />
<input name="roughness" type="vector2" nodename="haze_roughness" />
<input name="normal" type="vector3" interfacename="geometry_normal" />
<input name="tangent" type="vector3" interfacename="geometry_tangent" />
</generalized_schlick_bsdf>
<generalized_schlick_bsdf name="metal_bsdf_haze_tf" type="BSDF">
<input name="weight" type="float" nodename="specular_weight_nonnegative" />
<input name="color0" type="color3" nodename="metal_reflectivity" />
<input name="color82" type="color3" nodename="specular_color_clamped" />
<input name="roughness" type="vector2" nodename="haze_roughness" />
<input name="normal" type="vector3" interfacename="geometry_normal" />
<input name="tangent" type="vector3" interfacename="geometry_tangent" />
<input name="thinfilm_thickness" type="float" nodename="thin_film_thickness_nm" />
<input name="thinfilm_ior" type="float" nodename="thin_film_ior_nonnegative" />
</generalized_schlick_bsdf>
<mix name="metal_bsdf_haze_tf_mix" type="BSDF">
<input name="fg" type="BSDF" nodename="metal_bsdf_haze_tf" />
<input name="bg" type="BSDF" nodename="metal_bsdf_haze" />
<input name="mix" type="float" nodename="thin_film_weight_clamped" />
</mix>
<mix name="metal_bsdf_with_haze" type="BSDF">
<input name="fg" type="BSDF" nodename="metal_bsdf_haze_tf_mix" />
<input name="bg" type="BSDF" nodename="metal_bsdf_tf_mix" />
<input name="mix" type="float" nodename="specular_haze_clamped" />
</mix>

<mix name="base_substrate" type="BSDF">
<input name="fg" type="BSDF" nodename="metal_bsdf_tf_mix" />
<input name="fg" type="BSDF" nodename="metal_bsdf_with_haze" />
<input name="bg" type="BSDF" nodename="dielectric_base" />
<input name="mix" type="float" nodename="base_metalness_clamped" />
</mix>
Expand Down