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krohmerNVkrohmerNV
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add subsurface bsdf tests and apply weight in MDL implementation
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Lines changed: 112 additions & 10 deletions

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‎resources/Materials/TestSuite/pbrlib/bsdf/subsurface_bsdf.mtlx‎

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<?xml version="1.0"?>
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<materialx version="1.39">
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<nodegraph name="subsurface_1_common">
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<subsurface_bsdf name="subsurface_bsdf1" type="BSDF">
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<input name="weight" type="float" value="1.0" />
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<input name="color" type="color3" value="0.816, 0.140, 0.124" />
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<input name="radius" type="color3" value="1.0, 1.0, 1.0" />
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<input name="anisotropy" type="float" value="0.0" />
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</subsurface_bsdf>
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<surface name="surface1" type="surfaceshader">
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<input name="bsdf" type="BSDF" nodename="subsurface_bsdf1" />
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<input name="opacity" type="float" value="1.0" />
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</surface>
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<output name="out" type="surfaceshader" nodename="surface1" />
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</nodegraph>
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<!-- SSS radius of 1 cm assuming the scene units are in meters -->
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<nodegraph name="subsurface_2_radius_0_01">
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<subsurface_bsdf name="subsurface_bsdf1" type="BSDF">
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<input name="weight" type="float" value="1.0" />
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<input name="color" type="color3" value="0.816, 0.140, 0.124" />
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<input name="radius" type="color3" value="0.01, 0.01, 0.01" />
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<input name="anisotropy" type="float" value="0.0" />
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</subsurface_bsdf>
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<surface name="surface1" type="surfaceshader">
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<input name="bsdf" type="BSDF" nodename="subsurface_bsdf1" />
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<input name="opacity" type="float" value="1.0" />
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</surface>
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<output name="out" type="surfaceshader" nodename="surface1" />
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</nodegraph>
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<!-- SSS radius of 2.5 cm assuming the scene units are in meters -->
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<nodegraph name="subsurface_2_radius_0_025">
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<subsurface_bsdf name="subsurface_bsdf1" type="BSDF">
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<input name="weight" type="float" value="1.0" />
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<input name="color" type="color3" value="0.816, 0.140, 0.124" />
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<input name="radius" type="color3" value="0.025, 0.025, 0.025" />
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<input name="anisotropy" type="float" value="0.0" />
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</subsurface_bsdf>
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<surface name="surface1" type="surfaceshader">
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<input name="bsdf" type="BSDF" nodename="subsurface_bsdf1" />
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<input name="opacity" type="float" value="1.0" />
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</surface>
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<output name="out" type="surfaceshader" nodename="surface1" />
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</nodegraph>
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<!-- SSS radius of 5 m (thin gas) assuming the scene units are in meters -->
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<nodegraph name="subsurface_2_radius_5_0">
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<subsurface_bsdf name="subsurface_bsdf1" type="BSDF">
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<input name="weight" type="float" value="1.0" />
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<input name="color" type="color3" value="0.816, 0.140, 0.124" />
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<input name="radius" type="color3" value="5.0, 5.0, 5.0" />
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<input name="anisotropy" type="float" value="0.0" />
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</subsurface_bsdf>
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<surface name="surface1" type="surfaceshader">
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<input name="bsdf" type="BSDF" nodename="subsurface_bsdf1" />
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<input name="opacity" type="float" value="1.0" />
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</surface>
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<output name="out" type="surfaceshader" nodename="surface1" />
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</nodegraph>
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<nodegraph name="subsurface_3_weighted">
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<subsurface_bsdf name="subsurface_bsdf1" type="BSDF">
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<input name="weight" type="float" value="0.25" />
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<input name="color" type="color3" value="0.816, 0.140, 0.124" />
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<input name="radius" type="color3" value="1.0, 1.0, 1.0" />
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<input name="anisotropy" type="float" value="0.0" />
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</subsurface_bsdf>
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<surface name="surface1" type="surfaceshader">
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<input name="bsdf" type="BSDF" nodename="subsurface_bsdf1" />
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<input name="opacity" type="float" value="1.0" />
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</surface>
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<output name="out" type="surfaceshader" nodename="surface1" />
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</nodegraph>
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<nodegraph name="subsurface_4_forward">
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<subsurface_bsdf name="subsurface_bsdf1" type="BSDF">
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<input name="weight" type="float" value="1.0" />
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<input name="color" type="color3" value="0.816, 0.140, 0.124" />
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<input name="radius" type="color3" value="1.0, 1.0, 1.0" />
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<input name="anisotropy" type="float" value="0.9" />
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</subsurface_bsdf>
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<surface name="surface1" type="surfaceshader">
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<input name="bsdf" type="BSDF" nodename="subsurface_bsdf1" />
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<input name="opacity" type="float" value="1.0" />
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</surface>
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<output name="out" type="surfaceshader" nodename="surface1" />
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</nodegraph>
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<nodegraph name="subsurface_4_backward">
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<subsurface_bsdf name="subsurface_bsdf1" type="BSDF">
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<input name="weight" type="float" value="1.0" />
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<input name="color" type="color3" value="0.816, 0.140, 0.124" />
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<input name="radius" type="color3" value="1.0, 1.0, 1.0" />
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<input name="anisotropy" type="float" value="-0.9" />
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</subsurface_bsdf>
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<surface name="surface1" type="surfaceshader">
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<input name="bsdf" type="BSDF" nodename="subsurface_bsdf1" />
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<input name="opacity" type="float" value="1.0" />
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</surface>
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<output name="out" type="surfaceshader" nodename="surface1" />
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</nodegraph>
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</materialx>

‎source/MaterialXGenMdl/mdl/materialx/pbrlib_1_6.mdl‎

Lines changed: 8 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -340,7 +340,7 @@ export material mx_generalized_schlick_bsdf(
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);
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export material mx_subsurface_bsdf(
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float mxp_weight = 1.0 [[ anno::unused() ]],
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float mxp_weight = 1.0,
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color mxp_color = color(0.18),
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color mxp_radius = color(1.0),
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float mxp_anisotropy = 0.0,
@@ -351,22 +351,20 @@ export material mx_subsurface_bsdf(
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= let {
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// https://blog.selfshadow.com/publications/s2017-shading-course/imageworks/s2017_pbs_imageworks_slides_v2.pdf
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// Phase function eccentricity 'g' has been omitted here since we pass that directly
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// to anisotropic_vdf(directional_bias: g).
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// to anisotropic_vdf(directional_bias: g).
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color C = math::saturate(mxp_weight) * mxp_color;
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color albedo = color(4.09712) +
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(4.20863f * mxp_color) -
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(4.20863f * C) -
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math::sqrt(
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9.59217f +
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41.6808f * mxp_color +
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17.7126f * mxp_color * mxp_color);
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41.6808f * C +
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17.7126f * C * C);
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color albedo_sq = albedo * albedo;
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color white = color(1.0, 1.0, 1.0);
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color alpha = (white - albedo_sq) / (white - mxp_anisotropy * albedo_sq);
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color alpha =
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(white - albedo_sq) / (white - mxp_anisotropy * albedo_sq);
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color radius_inv = white / mxp_radius;
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color radius_inv = white / math::max(color(0.001), mxp_radius);
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color sigma_s = alpha * radius_inv;
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color sigma_a = radius_inv - sigma_s;

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