Read particle attribute info in an alembic cache and recreate instance in Maya ?

[emouillet]

Hi guys !

i would like to know if it' s possible to read directly the particle attributes stored in an alembic cache , and then recreate instancing inside Maya.

for exemple :

- i have 1000 houdini particles stored in an .abc file

- i have the following attributePP :  Cd, P, rot, scale 

I would like to read data from this cache and recreate instance geometry from that in Maya.

Is it possible to do this with Bifrost ?

Thanks for your time 

Cheers 

E

[emouillet · Accepted solution]

https://forums.autodesk.com/t5/bifrost-forum/export-instanced-geometry/td-p/8928903

Alembic export/import doesn't support instanced geometry, curves, strands, or even points.  Only one mesh.  

It is Not ! 

[emouillet]

As as side note, the last version of Maya i have check was 2016, we are now at Maya 2019 with a brand new dynamics solver. However those trivial things are still a nightmare to do in Maya for any FX artist that need to import their FX inside Maya : 

- import houdini particle with custom attributes inside maya 

- import animated curves with custom attributes inside maya 

- import houdini instance with correct transform info

I have a dream that one day , those 3 things will be done easily without banging our head against the wall.

There is Houdini Engine that Kinda be usable as an alternative, but it's expensive and not renderfarm friendly. 

Especially when at the end what we need is just a working alembic importer.

[marcus.nordenstam · Accepted solution]

Hi Emmanuel,

While it will be a bit longer until we have instances and curves support for Alembic, one of your desires can in fact be accomplished right now: Houdini particles with extra attributes into Bifrost.

If you export your Houdini particles as .VDB (a so-called "point VDB"), then you will be able to read in those particles with attributes into Bifrost.  Did you try that?

cheers

Marcus

[emouillet]

Hi Marcus,

Thanks for your answer, it is really helpful, as i didn't know that it was possible to store particle with vdb format. I though it only apply for volumes but i was wrong.  I will try with your methods. 

As you might have access to alembic plugin dev at AD. That would be great to finally have a proper importer / exporter, with all abc feature. something similar to what jcube or exocortex have done :

https://j-cube.jp/solutions/multiverse/

http://exocortex.com/products/crate

This is really a painful problem for FX artist , when you need to migrate your FX in Maya.

I hope Maya will make a real update to get a proper abc / vdb support natively with delaye load / pack geometrie .

Cheers 

E

[bflat]

Hi Marcus,

You say we can read VDB points in Bifrost, could anybody explain how to get the actual data into a maya particle node ?

When I try this, I get 2 problems :
1. The Houdini artist I work with exported a volume VDB with particles turned to a sdf and I can read this as a volume, but don't get if I can turn this into particles or how.
2. When we try to export points directly to a VDB, and I read it inside Bifrost, nothing seems to work. I get a 0 value at the points watchPoint.

I'm quite new to Bifrost, but uing Maya for more than 15 years, with a lot of particles and scripting.
Actually, I may script a little routine to recreate particles from mesh with vtx attributes in an alembic file.

I'll appreciate it if anybody has an explanation about this bifrost network issue.

Thanks,
Bastien.

[Grahame_Fuller]

Hi Bastien,

Are you using the latest version of Bifrost? We've made some fixes and improvements the VDB nodes in Bifrost 2.1.0.0. You can get the latest plug-in for your version of Maya from the Download Center.

Cheers,

gray

[bflat]

Thanks for your response, Gray. My version of Bifrost in Maya 2020 is now 2.1.0.0
Maybe the problem now is how the data is put in the vdb in the first place ?
It seems I don't have data in my pointVDB. size:0 at my watchpoint, vs size:3 for the volume VDB if we transfet the particle data in voxels via a sdf.

Anybody with good tips is walcome here 😉

Thanks.
Bastien.

[Christoph_Schaedl]

Yes some kind of tutorial would be great here. I get this question a lot on the internet.

[Grahame_Fuller]

Hi Bastien,

I managed to find a VDB point file from Houdini to test with, and confirmed that it imports OK into Bifrost. I can also import all the point samples from the OpenVDB download page, as well as round-trip VDB point files from Bifrost.

So, I am beginning to wonder whether there is an issue with the file from your colleague. Can you confirm whether it can be imported back into Houdini with no problems?

If that works and you still can't get it into Bifrost, is it possible for you to zip it up and attach it? I think it would be a good idea to start a new thread for that so that others can find it more easily if they are having similar problems, since this thread was originally about Alembic. Alternatively, you can send it to me on private chat if you prefer.

Cheers,

gray

[morten.bojsen-hansen]

Also worth mentioning, Bifrost has Alembic points and curves support since version 2.1.0.0 so you might want to try that again.

[bflat]

Thanks for all your replies.
We're curently looking at how they can output point data from Houdini, as I can effectively read very well the sample files from the openVdb website.

And also looking at the new possibilities around Alembic with the last version. That's awesome.
I think it closes pretty well this discussion about alembic files and particle attributes.

cheers,
Bastien.

[emouillet]

Hi guys , i was wondering if there are some progress on the alembic reader inside bifrost.

- is it possible to read alembic point cloud with per point attributes, and load them as particles to be able to render them directly with access to custom attributes, and also ability to instanciate geometry on those point inside bifrost ?

- is it now possible to read animated curves in alembic , and get access to custom per point attributes ?

Are there any startup 101 scenes that illustrates the process to do this , if it is possible ?

Thanks

[Christoph_Schaedl]

Have you seen the video from Bruce?

https://youtu.be/MVnaE9LnLQc

[emouillet]

Thanks a lot for the very fast answer oglu !

This links looks great , and if this statement is true 

"Simply put, now through bifrost's abc and vdb, we can communicate all data between Maya and Houdini. After solving the cache, you can use any software to render."

I will take the time to try all this, and if this statement is true, i will put some Champagne in the fridge , cause this will end a LOT of pain for many FX artist to enter their FX into Maya. Congrats to all the one involved at AD in making this FINALLY work !

THANKS !