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OBJ vs Alembic ram usage

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OBJ vs Alembic ram usage

Unread postby Ken_M » Fri Apr 03, 2020 3:37 pm

Hi,
I had a question about the RAM usage of OBJ and Alembic format.
I know a lot of the documentation goes over Clarisse's ability to work with Alembic as the preferred format.

I had a model I built in zbrush for a concept.
I thought the best way of exporting it was saving out as an FBX and then using another package to export that FBX as alembic to use in Clarisse.

The exported alembic is around 4GB and when Clarisse tries to load it the Ram on my system gradually climbs to its full 32 gb, gets to around 31.5gb and then crashes Clarisse.

If I save out all the dense/high res geo as a series of OBJs Clarisse has a very easy time loading. I wind up only using around 11 - 14 gb of my ram to bring it in.

Does Clarisse require more ram to open alembic files than it does for OBJs?

If I have a lot of high-res scanned models from megascans....
Is it better to save these out as OBJs instead of alembic? Initially I had gone through my library and re-saved a lot of my megascans downloads as alembic so they would take up less space on my hard drive (and I had assumed based on the documention that Clarisse has the easiest time with Alembic out of all the formats it can bring in) -- but if I'm trying to conserve limited ram perhaps this was a poor choice on my part?

Is it always better to use OBJ for high res static geometry or dense geometry from a sculpting program OR have I encountered some kind of issue with my alembic file?

Windows 10 64bit
Clarisse 4 Sp5

Thanks for the help!
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Re: OBJ vs Alembic ram usage

Unread postby dboude » Fri Apr 03, 2020 5:10 pm

Hi,

Alembic can handle more geometry properties than obj format. Perhaps you exported more data in the alembic file like normals or other data that FBX and Alembic can handle, which can explain this. Otherwise, if the same data are stored in alembic and obj there might be no difference at all.

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Re: OBJ vs Alembic ram usage

Unread postby Ken_M » Sat Apr 04, 2020 5:48 pm

Thanks Demian, I'll have to investigate more why heavy alembics seem to be crashing clarisse for me, but OBJs don't. Maybe I can upload a piece of my concept. I'll try to save something out later this weekend.
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Re: OBJ vs Alembic ram usage

Unread postby oddvisionary » Sat Apr 04, 2020 7:06 pm

Hello Ken,

I'm working here with as big if not bigger alembics sometimes and have no RAM issue with Clarisse. And I would highly not recommend OBJ with perhaps this exception: I'm also working a lot with Megascans (I am actually working for Quixel/Epic Games as a freelancer) and using OBJ is fine for single assets, such as a 3D high poly scan from the Megascans library. That said, in latest Bridge version, you should have the option to export in alembic and one-click-export to Clarisse directly.

This might be an isolated case scenario. Try with some high res Megascans alembic, re-download the asset in OBj and see if you have such drastic RAM differences. Also, verify you are using the latest Clarisse version.
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Re: OBJ vs Alembic ram usage

Unread postby Ken_M » Mon Apr 06, 2020 3:29 pm

Thanks for the reply, Oddvisionary.
That's some good info. I appreciate it.
Thanks for the tip about the latest bridge version. The bridge import into Clarisse works great.

Here was my export settings when saving an OBJ/FBX to Alembic for use in Clarisse. Maybe I'm doing something wrong?

alembic_export_settings_example_v001.JPG


And here's one of the free megascans asssets that I resaved as Alembic. Is there something wrong with my format or file? Maybe a checkbox I'm not clicking?

Edit: Just realized I had the normals checkbox clicked and Demian mentioned exporting normals could potentially be a problem?

https://www.dropbox.com/sh/jcaahj9jpsnt ... y34Ya?dl=0

Thank you for taking a look.
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Re: OBJ vs Alembic ram usage

Unread postby dboude » Mon Apr 06, 2020 7:59 pm

Hi,

No exporting normals take more weight, that's all. It's not a problem. The problem is that you let the subdivision surface checked. So when Clarisse loads the geometry, it subdivides the mesh. The resulting geometry is four times heavier.

Just uncheck it and re-export ;)

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Re: OBJ vs Alembic ram usage

Unread postby sam » Mon Apr 06, 2020 8:02 pm

I guess Cinema 4D export is buggy and force the geometry as if it was in SubD (because clearly your model doesn't look like it is) which is automatically translated to SubD in Clarisse.
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Re: OBJ vs Alembic ram usage

Unread postby oddvisionary » Tue Apr 07, 2020 9:41 pm

Ken_M wrote:Here was my export settings when saving an OBJ/FBX to Alembic for use in Clarisse. Maybe I'm doing something wrong?


Off-topic but I'm curious to see how does your scale looks like in Clarisse. If you put a 2x2m cube in Clarisse, after you imported your ABC from C4D, it might not match a 2x2m cube in C4D. Don't export the cube in the ABC but add it after in Clarisse, just to confirm your scale conversion is correct as C4D is by default in CM and Clarisse in M.
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Re: OBJ vs Alembic ram usage

Unread postby Ken_M » Wed Apr 08, 2020 9:35 pm

Thanks Demian and Sam. I'll re-save my megascans alembics without the subD checked. Thanks for helping me.

Hi Oddvisionary,
You're right. My scale is messed up on quite a few of my imports in my model library. I have a lot of old models from various software that are all saved to wrong the size if brought into Clarisse. I spent some time making library scene files in Clarisse and resizing tons of stuff in reference to a T-pose figure.
Going forward I'll follow your suggestion with importing a cube to see if the scale matches. The export scale in a bunch of packages I use still kind of confuses me. I'll try it your way to at least solve the c4D area.

Thankyou for the help!
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Re: OBJ vs Alembic ram usage

Unread postby oddvisionary » Tue Apr 14, 2020 2:43 am

Hello Ken

I've had a very weird experience with Cinema 4D unit system at the export. There are a few things that do not make sense to me.

My tip for C4D if the following:

1 • Once you are done doing changes in your Cinema 4D scene, make CTRL + D and set the unit to Meters
2 • DO NOT SAVE the project file in Cinema 4D once you've done the first time
3 • Export your Alembic (Ogawa)
4 • Set the unit in meters as well
5 • With a value of 0.01

I've tried more logical exports but they never worked. This one does.

Let me know if it helped you.

Best
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