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Add glTF PBR (#861)
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This PR adds a node definition and implementation of the glTF PBR material with the following extensions:
* KHR_materials_transmission
* KHR_materials_specular
* KHR_materials_ior
* KHR_materials_sheen
* KHR_materials_clearcoat
* KHR_materials_volume
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@proog128
proog128 authored Mar 14, 2022
1 parent 75e3edd commit b58042e
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263 changes: 263 additions & 0 deletions libraries/bxdf/gltf_pbr.mtlx
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<?xml version="1.0"?>
<materialx version="1.38">
<nodedef name="ND_gltf_pbr_surfaceshader" node="gltf_pbr" nodegroup="pbr" doc="glTF PBR" version="0.0.1" isdefaultversion="true">
<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" />
<input name="metallic" type="float" value="0" uimin="0" uimax="1" uiname="Metallic" uifolder="Base" />
<input name="roughness" type="float" value="0" uimin="0" uimax="1" uiname="Roughness" uifolder="Base" />
<input name="normal" type="vector3" defaultgeomprop="Nworld" uiname="Normal" uifolder="Base" />
<input name="occlusion" type="float" value="0" uimin="0" uimax="1" uiname="Occlusion" uifolder="Base" />
<input name="transmission" type="float" value="0" uimin="0" uimax="1" uiname="Transmission" uifolder="Base" />
<input name="specular" type="float" value="1" uimin="0" uimax="1" uiname="Specular" uifolder="Base" />
<input name="specular_color" type="color3" value="1, 1, 1" uimin="0, 0, 0" uisoftmax="1, 1, 1" uiname="Specular Color" uifolder="Base" />
<input name="ior" uniform="true" type="float" value="1.5" uimin="1" uisoftmax="3" uiname="Index of Refraction" uifolder="Base" />
<input name="alpha" type="float" value="0" uimin="0" uimax="1" uiname="Alpha" uifolder="Alpha" />
<input name="alpha_mode" uniform="true" type="integer" enum="OPAQUE, MASK, BLEND" enumvalues="0, 1, 2" value="0" uiname="Alpha Mode" uifolder="Alpha" />
<input name="alpha_cutoff" uniform="true" type="float" value="0.5" uimin="0" uimax="1" uiname="Alpha Cutoff" uifolder="Alpha" />
<input name="sheen_color" type="color3" value="0, 0, 0" uimin="0, 0, 0" uimax="1, 1, 1" uiname="Sheen Color" uifolder="Sheen" />
<input name="sheen_roughness" type="float" value="0" uimin="0" uimax="1" uiname="Sheen Roughness" uifolder="Sheen" />
<input name="clearcoat" type="float" value="0" uimin="0" uimax="1" uiname="Clearcoat" uifolder="Clearcoat" />
<input name="clearcoat_roughness" type="float" value="0" uimin="0" uimax="1" uiname="Clearcoat Roughness" uifolder="Clearcoat" />
<input name="clearcoat_normal" type="vector3" defaultgeomprop="Nworld" uiname="Clearcoat Normal" uifolder="Clearcoat" />
<input name="emissive" type="color3" value="0, 0, 0" uimin="0, 0, 0" uimax="1, 1, 1" uiname="Emissive" uifolder="Emission" />
<input name="thickness" uniform="false" type="float" uimin="0" uiname="Thickness" uifolder="Volume" />
<input name="attenuation_distance" uniform="true" type="float" uimin="0" uiname="Attenuation Distance" uifolder="Volume" />
<input name="attenuation_color" uniform="true" type="color3" value="1, 1, 1" uimin="0, 0, 0" uimax="1, 1, 1" uiname="Attenuation Color" uifolder="Volume" />
<output name="out" type="surfaceshader" />
</nodedef>

<nodegraph name="IMPL_gltf_pbr_surfaceshader" nodedef="ND_gltf_pbr_surfaceshader">
<!-- Volume -->

<convert name="attenuation_color_vec" type="vector3">
<input name="in" type="color3" interfacename="attenuation_color" />
</convert>

<ln name="ln_attenuation_color_vec" type="vector3">
<input name="in" type="vector3" nodename="attenuation_color_vec" />
</ln>

<divide name="ln_attenuation_color_vec_over_distance" type="vector3">
<input name="in1" type="vector3" nodename="ln_attenuation_color_vec" />
<input name="in2" type="float" interfacename="attenuation_distance" />
</divide>

<multiply name="attenuation_coeff" type="vector3">
<input name="in1" type="vector3" nodename="ln_attenuation_color_vec_over_distance" />
<input name="in2" type="float" value="-1" />
</multiply>

<anisotropic_vdf name="isotropic_volume" type="VDF">
<!-- No scattering yet, so absorption_coeff == attenuation_coeff -->
<input name="absorption" type="vector3" nodename="attenuation_coeff" />
<input name="scattering" type="vector3" value="0, 0, 0" />
<input name="anisotropy" type="float" value="0" />
</anisotropic_vdf>

<!-- Base layer -->

<!-- Compute F0 and F90 of dielectric component -->
<subtract name="one_minus_ior" type="float">
<input name="in1" type="float" value="1" />
<input name="in2" type="float" interfacename="ior" />
</subtract>

<add name="one_plus_ior" type="float">
<input name="in1" type="float" value="1" />
<input name="in2" type="float" interfacename="ior" />
</add>

<divide name="ior_div" type="float">
<input name="in1" type="float" nodename="one_minus_ior" />
<input name="in2" type="float" nodename="one_plus_ior" />
</divide>

<multiply name="dielectric_f0_from_ior" type="float">
<input name="in1" type="float" nodename="ior_div" />
<input name="in2" type="float" nodename="ior_div" />
</multiply>

<multiply name="dielectric_f0_from_ior_specular_color" type="color3">
<input name="in1" type="color3" interfacename="specular_color" />
<input name="in2" type="float" nodename="dielectric_f0_from_ior" />
</multiply>

<min name="clamped_dielectric_f0_from_ior_specular_color" type="color3">
<input name="in1" type="color3" nodename="dielectric_f0_from_ior_specular_color" />
<input name="in2" type="float" value="1" />
</min>

<multiply name="dielectric_f0" type="color3">
<input name="in1" type="color3" nodename="clamped_dielectric_f0_from_ior_specular_color" />
<input name="in2" type="float" interfacename="specular" />
</multiply>

<multiply name="dielectric_f90" type="color3">
<input name="in1" type="color3" value="1, 1, 1" />
<input name="in2" type="float" interfacename="specular" />
</multiply>

<!-- Roughness -->

<roughness_anisotropy name="roughness_uv" type="vector2">
<input name="roughness" type="float" interfacename="roughness" />
</roughness_anisotropy>

<!-- Dielectric -->

<oren_nayar_diffuse_bsdf name="diffuse_bsdf" type="BSDF">
<input name="color" type="color3" interfacename="base_color" />
<input name="normal" type="vector3" interfacename="normal" />
</oren_nayar_diffuse_bsdf>

<dielectric_bsdf name="transmission_bsdf" type="BSDF">
<input name="weight" type="float" value="1" />
<input name="tint" type="color3" interfacename="base_color" />
<input name="ior" type="float" interfacename="ior" />
<input name="roughness" type="vector2" nodename="roughness_uv" />
<input name="normal" type="vector3" interfacename="normal" />
<input name="scatter_mode" type="string" value="T" />
</dielectric_bsdf>

<generalized_schlick_bsdf name="reflection_bsdf" type="BSDF">
<input name="color0" type="color3" nodename="dielectric_f0" />
<input name="color90" type="color3" nodename="dielectric_f90" />
<input name="roughness" type="vector2" nodename="roughness_uv" />
<input name="normal" type="vector3" interfacename="normal" />
<input name="scatter_mode" type="string" value="R" />
</generalized_schlick_bsdf>

<mix name="transmission_mix" type="BSDF">
<input name="bg" type="BSDF" nodename="diffuse_bsdf" />
<input name="fg" type="BSDF" nodename="transmission_bsdf" />
<input name="mix" type="float" interfacename="transmission" />
</mix>

<layer name="dielectric_bsdf" type="BSDF">
<input name="top" type="BSDF" nodename="reflection_bsdf" />
<input name="base" type="BSDF" nodename="transmission_mix" />
</layer>

<!-- Metal -->

<generalized_schlick_bsdf name="metal_bsdf" type="BSDF">
<input name="color0" type="color3" interfacename="base_color" />
<input name="color90" type="color3" value="1, 1, 1" />
<input name="roughness" type="vector2" nodename="roughness_uv" />
<input name="normal" type="vector3" interfacename="normal" />
</generalized_schlick_bsdf>

<!-- Dielectric/metal mix -->

<mix name="base_mix" type="BSDF">
<input name="bg" type="BSDF" nodename="dielectric_bsdf" />
<input name="fg" type="BSDF" nodename="metal_bsdf" />
<input name="mix" type="float" interfacename="metallic" />
</mix>

<!-- Sheen layer -->

<!-- Compute sheen intensity = max(sheen_color.r, sheen_color.g, sheen_color.b) -->
<extract name="sheen_color_r" type="float">
<input name="in" type="color3" interfacename="sheen_color" />
<input name="index" type="integer" value="0" />
</extract>

<extract name="sheen_color_g" type="float">
<input name="in" type="color3" interfacename="sheen_color" />
<input name="index" type="integer" value="1" />
</extract>

<extract name="sheen_color_b" type="float">
<input name="in" type="color3" interfacename="sheen_color" />
<input name="index" type="integer" value="2" />
</extract>

<max name="sheen_color_max_rg" type="float">
<input name="in1" type="float" nodename="sheen_color_r" />
<input name="in2" type="float" nodename="sheen_color_g" />
</max>

<max name="sheen_intensity" type="float">
<input name="in1" type="float" nodename="sheen_color_max_rg" />
<input name="in2" type="float" nodename="sheen_color_b" />
</max>

<multiply name="sheen_roughness_sq" type="float">
<input name="in1" type="float" interfacename="sheen_roughness" />
<input name="in2" type="float" interfacename="sheen_roughness" />
</multiply>

<divide name="sheen_color_normalized" type="color3">
<input name="in1" type="color3" interfacename="sheen_color" />
<input name="in2" type="float" nodename="sheen_intensity" />
</divide>

<sheen_bsdf name="sheen_bsdf" type="BSDF">
<input name="weight" type="float" nodename="sheen_intensity" />
<input name="color" type="color3" nodename="sheen_color_normalized" />
<input name="roughness" type="float" nodename="sheen_roughness_sq" />
<input name="normal" type="vector3" interfacename="normal" />
</sheen_bsdf>

<layer name="sheen_layer" type="BSDF">
<input name="top" type="BSDF" nodename="sheen_bsdf" />
<input name="base" type="BSDF" nodename="base_mix" />
</layer>

<!-- Clearcoat -->

<roughness_anisotropy name="clearcoat_roughness_uv" type="vector2">
<input name="roughness" type="float" interfacename="clearcoat_roughness" />
</roughness_anisotropy>

<dielectric_bsdf name="clearcoat_bsdf" type="BSDF">
<input name="weight" type="float" interfacename="clearcoat" />
<input name="roughness" type="vector2" nodename="clearcoat_roughness_uv" />
<input name="ior" type="float" value="1.5"/>
<input name="normal" type="vector3" interfacename="clearcoat_normal" />
</dielectric_bsdf>

<layer name="clearcoat_layer" type="BSDF">
<input name="top" type="BSDF" nodename="clearcoat_bsdf" />
<input name="base" type="BSDF" nodename="sheen_layer" />
</layer>

<!-- Emission -->

<uniform_edf name="emission" type="EDF">
<input name="color" type="color3" interfacename="emissive" />
</uniform_edf>

<!-- Alpha -->

<ifgreatereq name="opacity_mask_cutoff" type="float">
<input name="value1" type="float" interfacename="alpha" />
<input name="value2" type="float" interfacename="alpha_cutoff" />
<input name="in1" type="float" value="1" />
<input name="in2" type="float" value="0" />
</ifgreatereq>

<ifequal name="opacity_mask" type="float">
<input name="value1" type="integer" interfacename="alpha_mode" />
<input name="value2" type="integer" value="1" />
<input name="in1" type="float" nodename="opacity_mask_cutoff" />
<input name="in2" type="float" interfacename="alpha" />
</ifequal>

<ifequal name="opacity" type="float">
<input name="value1" type="integer" interfacename="alpha_mode" />
<input name="value2" type="integer" value="0" />
<input name="in1" type="float" value="1" />
<input name="in2" type="float" nodename="opacity_mask" />
</ifequal>

<!-- Surface -->

<surface name="shader_constructor" type="surfaceshader">
<input name="bsdf" type="BSDF" nodename="clearcoat_layer" />
<input name="edf" type="EDF" nodename="emission" />
<input name="opacity" type="float" nodename="opacity" />
</surface>
<output name="out" type="surfaceshader" nodename="shader_constructor" />
</nodegraph>
</materialx>
29 changes: 29 additions & 0 deletions resources/Materials/Examples/GltfPbr/gltf_pbr_default.mtlx
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<?xml version="1.0"?>
<materialx version="1.38" colorspace="lin_rec709">
<gltf_pbr name="SR_default" type="surfaceshader">
<input name="base_color" type="color3" value="0.8, 0.8, 0.8" />
<input name="metallic" type="float" value="0" />
<input name="roughness" type="float" value="0" />
<input name="normal" type="vector3" value="0, 0, 1" />
<input name="occlusion" type="float" value="0" />
<input name="transmission" type="float" value="0" />
<input name="specular" type="float" value="1" />
<input name="specular_color" type="color3" value="1, 1, 1" />
<input name="ior" type="float" value="1.5" />
<input name="alpha" type="float" value="1" />
<input name="alpha_mode" type="integer" value="0" />
<input name="alpha_cutoff" type="float" value="0.5" />
<input name="sheen_color" type="color3" value="0, 0, 0" />
<input name="sheen_roughness" type="float" value="0" />
<input name="clearcoat" type="float" value="0" />
<input name="clearcoat_roughness" type="float" value="0" />
<input name="clearcoat_normal" type="vector3" value="0, 0, 1" />
<input name="emissive" type="color3" value="0, 0, 0" />
<input name="thickness" type="float" value="0" />
<input name="attenuation_distance" type="float" value="100000" />
<input name="attenuation_color" type="color3" value="0, 0, 0" />
</gltf_pbr>
<surfacematerial name="Default" type="material">
<input name="surfaceshader" type="surfaceshader" nodename="SR_default" />
</surfacematerial>
</materialx>

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