usdMtlx ignores an active file prefix

[willmuto-lucasfilm]

Description of Issue

usdMtlx ignores an active file prefix defined by the fileprefix attribute in a parent tag.

Steps to Reproduce

1. Given the following MaterialX file (ExpandFilePrefix.mtlx):

<?xml version="1.0"?>
<materialx version="1.36">
    <nodedef name="ND_layerShader" type="surfaceshader" node="layerShader">
        <input name="in" type="filename"/>
    </nodedef>
    <material name="noPrefix">
        <shaderref name="layered_sr" node="layerShader">
            <bindinput name="in" type="filename" value="img1.jpg"/>
        </shaderref>
    </material>
    <material name="prefixInValue">
        <shaderref name="layered_sr" node="layerShader">
            <bindinput name="in" type="filename" value="images/img2.jpg"/>
        </shaderref>
    </material>
    <material name="prefixInAttr"  fileprefix="images">
        <shaderref name="layered_sr" node="layerShader">
            <bindinput name="in" type="filename" value="img2.jpg"/>
        </shaderref>
    </material>
</materialx>

And running the following python code:

from pxr import Usd, UsdShade, Sdf
stage = Usd.Stage.CreateInMemory()
stage = stage.Open('ExpandFilePrefix.mtlx')
material_noprefix = UsdShade.Material.Get(stage, Sdf.Path('/MaterialX/Materials/noPrefix'))
inputs = material_noprefix.GetInputs()
for i in inputs:
     print i.GetFullName(), i.Get().resolvedPath

material_prefixed1 = UsdShade.Material.Get(stage, Sdf.Path('/MaterialX/Materials/prefixInValue))
inputs = material_prefixed1.GetInputs()
for i in inputs:
     print i.GetFullName(), i.Get().resolvedPath

material_prefixed2 = UsdShade.Material.Get(stage, Sdf.Path('/MaterialX/Materials/prefixInAttr))
inputs = material_prefixed2.GetInputs()
for i in inputs:
     print i.GetFullName(), i.Get().resolvedPath

Returns the following results:

inputs:in /home/wmuto/usd_fileprefix/img1.jpg
inputs:in /home/wmuto/usd_fileprefix/images/img2.jpg
inputs:in 

This fix ensures that the fileprefix attribute is respected:

inputs:in /home/wmuto/usd_fileprefix/img1.jpg
inputs:in /home/wmuto/usd_fileprefix/images/img2.jpg
inputs:in /home/wmuto/usd_fileprefix/images/img2.jpg

I have a fix which I will be submitting a pull request for shortly!

System Information (OS, Hardware)

Linux RHEL7

Package Versions

Build Flags

[jilliene]

Filed as internal issue #USD-5571

[Derek-Nvidia]

We've recently encountered this same issue. This ticket remains open, however the related ticket #977 was closed w/o the change being merged. Is there any particular reason why? I have a fix that I can polish up and contribute ; however I wanted to make sure I understand the complete history.

[pmolodo]

Just to help demonstrate that this is still an issue as of 23.08, I adapted @willmuto-lucasfilm 's original reproduction code for python3, and made it self-contained (ie, no need to download anything else):

import os
import tempfile

from pxr import Sdf, Usd, UsdShade

mtlx_contents = """\
<?xml version="1.0"?>
<materialx version="1.36">
    <nodedef name="ND_layerShader" type="surfaceshader" node="layerShader">
        <input name="in" type="filename"/>
    </nodedef>
    <material name="noPrefix">
        <shaderref name="layered_sr" node="layerShader">
            <bindinput name="in" type="filename" value="img1.jpg"/>
        </shaderref>
    </material>
    <material name="prefixInValue">
        <shaderref name="layered_sr" node="layerShader">
            <bindinput name="in" type="filename" value="images/img2.jpg"/>
        </shaderref>
    </material>
    <material name="prefixInAttr" fileprefix="images">
        <shaderref name="layered_sr" node="layerShader">
            <bindinput name="in" type="filename" value="img2.jpg"/>
        </shaderref>
    </material>
</materialx>"""


with tempfile.TemporaryDirectory() as tempdir:
    os.chdir(tempdir)

    # create the necessary files
    mtlx_path = "ExpandFilePrefix.mtlx"
    with open(mtlx_path, "w") as writer:
        writer.write(mtlx_contents)

    stage = Usd.Stage.CreateInMemory()
    stage = stage.Open(mtlx_path)

    for mat_path, expected_img in [
        ("/MaterialX/Materials/noPrefix", "img1.jpg"),
        ("/MaterialX/Materials/prefixInValue", "images/img2.jpg"),
        ("/MaterialX/Materials/prefixInAttr", "images/img2.jpg"),
    ]:
        material = UsdShade.Material.Get(stage, mat_path)
        input = material.GetInput("in")
        actual_img = input.Get().path
        print(actual_img)
        if actual_img != expected_img:
            print(f"    !!!! Expected: {expected_img} !!!!")

This outputs:

img1.jpg
images/img2.jpg
img2.jpg
    !!!! Expected: images/img2.jpg !!!!

[willmuto-lucasfilm]

Hi @pmolodo @Derek-Nvidia , my apologies for the confusion here! Back when I originally submitted the PR there was some restructuring of the project and from what I remember I was going to open a new PR after the rebase which is why the related ticket was closed. I never got around to sorting this out after I wrapped my show at the time and went on holiday after, and it fell off my radar.

I can dust off the change #977 or if you have a change ready to roll @Derek-Nvidia please feel free to use that. Again, my apologies!

[Derek-Nvidia]

Hi,
i have created an MR for this: #2660