Instancing directly from disk

[ch3]

Hi,
I've managed to instance geometry using the instanceSOP and render within houdini. But ideally we need to export VRay proxy vrmesh file and render in Maya.
It seems like unless the instanced geometry exist within houdini, any geometry referenced directly from dist (.vrmesh, .bgeo.sc, .abc) isn't working on the maya side, even though they render with Matra.
Am I missing something? I've also struggle to find detailed documentation on instancing.

thank you

[Gosho.Genchev]

Hello,

if I'm understanding correctly, you are trying to use the Proxy Export SOP to export e.g. packed alembics as a vrmesh? For example, Alembic SOP -> Copy -> Proxy Export ?

Are you using Houdini Indie ? If not, you may be better off using the export VRScene option on the V-Ray Renderer -> Export tab. It would be much simpler to assign materials in Houdini and carry them over with the VRScene.

To answer your question specifically - your observations are correct - this does not work at the moment with the Proxy Export SOP. I will ping the devs about the issue.

Am I missing something? I've also struggle to find detailed documentation on instancing.

Indeed, sadly at the moment there isn't much info on this topic in the documentation.

Hope that helps!

[bdancer]

ch3, is it an option to export vrscene file and use "VRayScene Manager" in Maya? https://docs.chaosgroup.com/display/VRAY4MAYA/VRayScene
Also will be great to have a bit more details cause I don't fully understand the issue.
You could always bake Alembic out of Houdini as well...

[ch3]

Gosho, yes the workflow is
Alembic animated geometry instanced onto several hundred particles, which need to be exported to maya for rendering. I can export smaller simulation as alembic, but that doesn't scale up much and has other issues.

Since it's an animated asset, each point has a different time offset for variation so referencing a file directly from disk makes it easier to pick the right frame for each one. At least that's how I've done it before using Mantra or arnold (setting s@instancepath to a sequence of .bgeo.sc or .ass files).


By the way we are using the full houdini FX license here. I tried the Export VRay Proxy UI that there is in the VRay shelf, but I get the error below, even with a simple polygon sphere.
testInstancing_01 :$ Calling: vrayproxy -n /mnt/..../testInstancing_01/testSphere.vrmesh -f -t -T 3.0 -F 100.0 -H 100.0 -X 20000.0 /obj/geo1
Failed to create ROP for export

For the time being I will try to bring the animation as individual frames in houdini and reference each different node from the scene.

[bdancer]

ch3, give a try to vrscene export. This will preserve Alembic and shaders and everything.

[ch3]

I can't find an option or tool anywhere in houdini to export .vrscene files, only .vrmesh
I am going through the docs and I can't find anything relevant there either.


The Create V-Ray Proxy UI on the shelf (https://docs.chaosgroup.com/display/...te+V-Ray+Proxy) gives me the error below with any kind of object I've tried so far.
Calling: vrayproxy -n /mnt/burnside/JOBS/19-0721_childrens_hospital_co/cho/cho_250/geo/testInstancing_01/object.vrmesh -f -t -T 3.0 -F 100.0 -H 100.0 -X 20000.0 /obj/object
Failed to create ROP for export

When I use a vrayproxy ROP node I can export plain houdini geometry, but any alembic files I've tried to export while still packed don't render on the maya side.


For simplicity, I did both these test with a plain object, not instancing.

[bdancer]

> I can't find an option or tool anywhere in houdini to export .vrscene files, only .vrmesh

ROP -> Export Settings -> Export Mode -> "Export" or "Export & Render"

> When I use a vrayproxy ROP node I can export plain houdini geometry, but any alembic files.

So you want to export packed Alembic into proxy? That won't work. You can't have abc references inside the vrmesh file. You can't have any references inside the vrmesh file. Vrmesh files are only for mesh, hair and particles.

[ch3]

Oh I see, I can export to VRscene using the renderROP. Makes sense.
thank you for the clarification