My troubles with the LOPS Tutorial

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Hi, I'm currently doing the LOPS tutorial from the documentation Your text to link here… [www.sidefx.com] and in the fifth part, I've run into a problem right at the beginning, when loading the USD files.

In the first step, I add the Sublayer node, point it to one of the files I created in part 4. I get the lights and cameras I created previously, even the disabled Layout lights, but no geometry, also no error message. I first chalked it up to the layer break, thinking, that I only imported the layer I created in tutorial 4 and would have to import the prims before the Layer Break node separately.
In the next step, I added a Reference node, where I referenced another one of the scenes from the previous tutorial, but this time, the node threw a warning at me and didn't import anything. This is the warning:
Unresolved reference path <defaultPrim> on prim @anon:0000000070B22200:root.usd@,@anon:0000000070B23B00:root-session.usda@</Scene>. (recomposing stage on stage @anon:0000000070B22200:root.usd@ <000000017C7D9600>)

I also tried to import back the Shelf asset USD from tutorial 2 and that also throws warnings and doesn't load anything. What I get is a bunch of these, one for every asset in the assembly:
Could not open asset @d:/temp/Houdini Solaris Tutorial/LOPS_DEMO_FILES/Library/Assets/BookShelves/BookShelfAsset.usdlc@ for reference on prim @d:/temp/Houdini Solaris Tutorial/tutorials/PackedShelves.usdlc@,@anon:00000000096C1300ackedShelves-session.usda@</BookShelves/LeftShelf>. (instantiating stage on stage @d:/temp/Houdini Solaris Tutorial/tutorials/PackedShelves.usdlc@ <00000000EFC27700>)

The pre-made instanced shelves asset from the tutorial files works just fine though.
Any Idea, where I might start looking for the cause of this problem?

Thanks in advance.
Cheers,
Ivan
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Hi there, I wrote the tutorials, so maybe I can help. Can you post the hip files, the ones for both tutorial four and five? If you want you can PM me.
Sean Lewkiw
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The problem probably comes from differences between the licenses, if you are on Indie or Apprentice . USD files that came with the tutorial refer to other USD files in the structure. But you if are Indie, the files you create and reference are USDLC files. If you in part 4 start from USD tutorial file, and then prune/add/sublayer/refer over that original files with your USDLC stuff, you will get these kind of errors…
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Ah, thanks. So the logic behind the downwards compatibility of the licences is different from the .hip files? But yeah, that would explain a lot.

Thanks.
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One thing I didn't mention originally in the tutorials (because I did not know at the time) was that yes, indeed, your usd files will be “usdlc” files. Even if you explicitly use “usd” as the extension, Houdini will save out .usdlc. However, you will be able to load them back into Houdini w/o problem. I will update the tutorials to explain this.

Looking at your files ivanmalek, the problem is in your lops_tutorial_4.hip file… if you wire the first input of the merge SOP into the “Seq_lighting” LOP and not the “layerbreak” and save out your USD again, it should all work. By wiring in the layerbreak, you were basically wiring nothing into the first input of the merge LOP.

Please try that and I believe tutorial 5 will work for you.

Sean
Sean Lewkiw
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mrCatfish
Hi there, I wrote the tutorials, so maybe I can help. Can you post the hip files, the ones for both tutorial four and five? If you want you can PM me.

Just wanted to thanks Sean for the great materials/tutorials you provided with the release. Hopefully we can see more on this. I would love to know more on more advanced topics:

- how to setup the structure/data for the best performance, meaning how much stuff to layer to separate usd files/layers vs what to keep together in one usd file, for single asset, for example a car model. What are the common practices.

- Does it makes sense to keep the proxy(viewport representation) in separe usd file and have it reference as payload in the master “Asset.usd” file, or does it always load the proxy anyways?

- same for collision proxy, can that be payloaded too?

- Do we get faster read/open times on scene, when the materials are references in separate material.usd and viewport does not show textures? does Houdini really just loads the geo, and material/textures as payload are still on disk until the render?

-For the variants, If the Asset is geo heavy, is it common practice to save variants in separate USD files too? what if there is different material for each variant too - pro/cons of keeping per variant material in separate file versus all variant materials in one usd file. Are there some real performance differences at large scale setups or is the difference negligible in this case?

thank you
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These are all great questions and definitely something I think that needs to be addressed. The tutorials I did were definitly “the least you need to know.” I'm going to add your questions to a list of things to address in a masterclass, thanks for the suggestions.
Sean Lewkiw
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Thank you, looking forward for the masterclass.
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Hi Sean,

thanks for your help both here and in the PMs. Everything works as described in the tutorials now on my end as well.
And also thanks Peter for chiming in.

Cheers,
Ivan
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