Connections between nodes with multiple outputs ("multioutput") are not correctly handled

[kwokcb]

Issue

Separate and combine types and connections are improperly set / created

Environment

Tested with 0.4.1.

Test

If you create a separate node and then a combine node and connect the combine to a color3, the

1. Separate node remains the incorrect type of "float" - which has no definition
2. The input connections on the combine node do not specify which output to route to the combine.
   Perhaps this is a general "multioutput" issue?

Errors when the document get's validated.

Node interface doesn't support this output type: <separate3 name="Separate3" type="float" xpos="-7.002825605060728" ypos="2.48722845391956">
Mismatched types in port connection: <input name="base" type="float" value="1" nodegraph="NG_main" output="output_Combine3_out">

Could not find a nodedef for node 'Separate3'
Could not find a nodedef for node 'Separate3'

This is the resulting MaterialX file:

<?xml version="1.0"?>
<materialx version="1.38">
  <nodegraph name="NG_main">
    <separate3 name="Separate3" type="float" xpos="-7.002825605060728" ypos="2.48722845391956">
      <input name="in" type="color3" value="0, 0.894118, 0.14902" />
    </separate3>
    <combine3 name="Combine3" type="color3" xpos="-4.030665817358112" ypos="2.0648689051407674">
      <input name="in1" type="float" value="0" nodename="Separate3" />
      <input name="in2" type="float" value="0" nodename="Separate3" />
      <input name="in3" type="float" value="0" nodename="Separate3" />
    </combine3>
    <output name="output_Combine3_out" type="color3" nodename="Combine3" />
  </nodegraph>
  <surfacematerial name="USD_Default" type="material" xpos="3.6367873479362176" ypos="0.9333624596469625">
    <input name="surfaceshader" type="surfaceshader" nodename="Standard_surface" />
  </surfacematerial>
  <standard_surface name="Standard_surface" type="surfaceshader" xpos="-1.3527374062034248" ypos="1.0335230787321623">
    <input name="base" type="float" value="1" nodegraph="NG_main" output="output_Combine3_out" />
    <input name="base_color" type="color3" value="0.8, 0.8, 0.8" />
    <input name="diffuse_roughness" type="float" value="0" />
    <input name="metalness" type="float" value="0.8" />
    <input name="specular" type="float" value="1" />
    <input name="specular_color" type="color3" value="1, 1, 1" />
    <input name="specular_roughness" type="float" value="0.1" />
    <input name="specular_IOR" type="float" value="1.5" />
    <input name="specular_anisotropy" type="float" value="0" />
    <input name="specular_rotation" type="float" value="0" />
    <input name="transmission" type="float" value="0" />
    <input name="transmission_color" type="color3" value="1, 1, 1" />
    <input name="transmission_depth" type="float" value="0" />
    <input name="transmission_scatter" type="color3" value="0, 0, 0" />
    <input name="transmission_scatter_anisotropy" type="float" value="0" />
    <input name="transmission_dispersion" type="float" value="0" />
    <input name="transmission_extra_roughness" type="float" value="0" />
    <input name="subsurface" type="float" value="0" />
    <input name="subsurface_color" type="color3" value="1, 1, 1" />
    <input name="subsurface_radius" type="color3" value="1, 1, 1" />
    <input name="subsurface_scale" type="float" value="1" />
    <input name="subsurface_anisotropy" type="float" value="0" />
    <input name="sheen" type="float" value="0" />
    <input name="sheen_color" type="color3" value="1, 1, 1" />
    <input name="sheen_roughness" type="float" value="0.3" />
    <input name="coat" type="float" value="1" />
    <input name="coat_color" type="color3" value="0.6, 0.45, 1" />
    <input name="coat_roughness" type="float" value="0.1" />
    <input name="coat_anisotropy" type="float" value="0" />
    <input name="coat_rotation" type="float" value="0" />
    <input name="coat_IOR" type="float" value="2.5" />
    <input name="coat_normal" type="vector3" value="0, 0, 0" />
    <input name="coat_affect_color" type="float" value="0" />
    <input name="coat_affect_roughness" type="float" value="0" />
    <input name="thin_film_thickness" type="float" value="0" />
    <input name="thin_film_IOR" type="float" value="1.5" />
    <input name="emission" type="float" value="0" />
    <input name="emission_color" type="color3" value="1, 1, 1" />
    <input name="opacity" type="color3" value="1, 1, 1" />
    <input name="thin_walled" type="boolean" value="false" />
    <input name="normal" type="vector3" value="0, 0, 0" />
    <input name="tangent" type="vector3" value="0, 0, 0" />
  </standard_surface>
</materialx>

[RichardFrangenberg]

Thanks for reporting this.
I created a branch with a fix for this: https://github.com/PrismPipeline/QuiltiX/tree/fix_multi_output_nodes
Feel free to test that change.

The separate node has now the type "multioutput" and it works fine with Storm:

However the generated MaterialX file has a validation error:
No output found for port connection: <input name="in2" type="float" value="0" output="outg" nodename="Separate3"

Do you know what this means and how to fix it @kwokcb ?
The generated xml data looks correct to me and USD can load the file without problem. Could it be that there is a problem in the validator?
This is the generated xml data:

<?xml version="1.0"?>
<materialx version="1.38">
  <nodegraph name="NG_main">
    <separate3 name="Separate3" type="multioutput" xpos="-6.323393349156183" ypos="0.4079608612358828">
      <input name="in" type="color3" value="1, 1, 1" />
      <output name="outr" type="float" />
      <output name="outg" type="float" />
      <output name="outb" type="float" />
    </separate3>
    <combine3 name="Combine3" type="color3" xpos="-3.9209571663226512" ypos="0.5439478149811771">
      <input name="in1" type="float" value="0" />
      <input name="in2" type="float" value="0" output="outg" nodename="Separate3" />
      <input name="in3" type="float" value="0" />
      <output name="out" type="color3" />
    </combine3>
    <output name="output_Combine3_out" type="color3" nodename="Combine3" />
  </nodegraph>
  <surfacematerial name="USD_Default" type="material" xpos="2.1875" ypos="0.0">
    <input name="surfaceshader" type="surfaceshader" nodename="Standard_surface" />
    <output name="out" type="material" />
  </surfacematerial>
  <standard_surface name="Standard_surface" type="surfaceshader" xpos="-1.5775000000000001" ypos="0.0">
    <input name="base" type="float" value="1" />
    <input name="base_color" type="color3" value="0.8, 0.8, 0.8" nodegraph="NG_main" output="output_Combine3_out" />
    <input name="diffuse_roughness" type="float" value="0" />
    <input name="metalness" type="float" value="0.8" />
    <input name="specular" type="float" value="1" />
    <input name="specular_color" type="color3" value="1, 1, 1" />
    <input name="specular_roughness" type="float" value="0.1" />
    <input name="specular_IOR" type="float" value="1.5" />
    <input name="specular_anisotropy" type="float" value="0" />
    <input name="specular_rotation" type="float" value="0" />
    <input name="transmission" type="float" value="0" />
    <input name="transmission_color" type="color3" value="1, 1, 1" />
    <input name="transmission_depth" type="float" value="0" />
    <input name="transmission_scatter" type="color3" value="0, 0, 0" />
    <input name="transmission_scatter_anisotropy" type="float" value="0" />
    <input name="transmission_dispersion" type="float" value="0" />
    <input name="transmission_extra_roughness" type="float" value="0" />
    <input name="subsurface" type="float" value="0" />
    <input name="subsurface_color" type="color3" value="1, 1, 1" />
    <input name="subsurface_radius" type="color3" value="1, 1, 1" />
    <input name="subsurface_scale" type="float" value="1" />
    <input name="subsurface_anisotropy" type="float" value="0" />
    <input name="sheen" type="float" value="0" />
    <input name="sheen_color" type="color3" value="1, 1, 1" />
    <input name="sheen_roughness" type="float" value="0.3" />
    <input name="coat" type="float" value="1" />
    <input name="coat_color" type="color3" value="0.6, 0.45, 1" />
    <input name="coat_roughness" type="float" value="0.1" />
    <input name="coat_anisotropy" type="float" value="0" />
    <input name="coat_rotation" type="float" value="0" />
    <input name="coat_IOR" type="float" value="2.5" />
    <input name="coat_normal" type="vector3" value="0, 0, 0" />
    <input name="coat_affect_color" type="float" value="0" />
    <input name="coat_affect_roughness" type="float" value="0" />
    <input name="thin_film_thickness" type="float" value="0" />
    <input name="thin_film_IOR" type="float" value="1.5" />
    <input name="emission" type="float" value="0" />
    <input name="emission_color" type="color3" value="1, 1, 1" />
    <input name="opacity" type="color3" value="1, 1, 1" />
    <input name="thin_walled" type="boolean" value="false" />
    <input name="normal" type="vector3" value="0, 0, 0" />
    <input name="tangent" type="vector3" value="0, 0, 0" />
    <output name="out" type="surfaceshader" />
  </standard_surface>
</materialx>

[kwokcb]

• I tried the branch but the graph shows up unconnected on load (first version):
  

• The error you're encountering appears to be when trying to make connection between the upstream output and input. By default the node will not create it's outputs (outr, outg, outb) so when you try to connect there is no output port on the upstream node.

It seems the MaterialX save is adding in the outputs for every node (outr, outg, outb) after which the output can be found. I assume USD conversion is adding outputs as needed when converting to UsdShade.

I think a more robust mechanism is to add the output if it's not there when loading.

[RichardFrangenberg]

Hey @kwokcb , I added a new commit, which fixes the problems when loading the mtlx file. Could you give it a try?
The validation warning is still there. It still looks like a problem in the validator to me.
However the material updates fine for me in Storm.

[kwokcb]

Thanks @RichardFrangenberg
I'll take a look at it as soon as I can. If there is a validation error, I can take this up in core MaterialX :)