Standard surface -> glTF PBR translations: sheen roughness inconsistency

[bowald]

Roughness is not translated properly from standard surface to glTF PBR using the translation graphs.

The issue seems to be that glTF PBR squares roughness before sheen_bsdf and translation graph do not handle that. Fix is coming in a PR.

Screenshots of a black material with a red sheen effect with sheen roughness 0.5

Standard surface	Translated to glTF PBR	Diff

Test material

<?xml version="1.0"?>
<materialx version="1.39" colorspace="lin_rec709">
  <constant name="sheen_intensity2" type="float" xpos="-0.144928" ypos="-6.344828">
    <input name="value" type="float" value="1" />
  </constant>
  <constant name="sheen_color2" type="color3" xpos="0.246377" ypos="-4.982759">
    <input name="value" type="color3" value="1, 0, 0" />
  </constant>
  <constant name="sheen_roughness2" type="float" xpos="0.362319" ypos="-3.310345">
    <input name="value" type="float" value="0.5" />
  </constant>
  <gltf_pbr name="issue_material2" type="surfaceshader" xpos="11.565217" ypos="3.370690">
    <input name="base_color" type="color3" value="0, 0, 0" />
    <input name="sheen_color" type="color3" output="sheen_color_out" nodename="standard_surface_to_gltf_pbr" />
    <input name="sheen_roughness" type="float" output="sheen_roughness_out" nodename="standard_surface_to_gltf_pbr" />
    <input name="metallic" type="float" value="0" />
    <input name="specular_color" type="color3" value="1, 1, 1" />
    <input name="specular" type="float" value="0" />
  </gltf_pbr>
  <standard_surface name="standard_surface_surfaceshader2" type="surfaceshader" xpos="11.318841" ypos="-8.551724">
    <input name="base_color" type="color3" value="0, 0, 0" />
    <input name="specular_roughness" type="float" value="1" />
    <input name="sheen" type="float" output="out" nodename="sheen_intensity2" />
    <input name="sheen_roughness" type="float" output="out" nodename="sheen_roughness2" />
    <input name="sheen_color" type="color3" output="out" nodename="sheen_color2" />
    <input name="specular" type="float" value="0" />
  </standard_surface>
  <standard_surface_to_gltf_pbr name="standard_surface_to_gltf_pbr" type="multioutput" xpos="6.231884" ypos="-0.060345">
    <input name="sheen_roughness" type="float" nodename="sheen_roughness2" />
    <input name="sheen_color" type="color3" nodename="sheen_color2" />
    <input name="sheen" type="float" nodename="sheen_intensity2" />
  </standard_surface_to_gltf_pbr>
</materialx>