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Per-Frame Alembic export

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Hi!

 

I am exporting meshed FLIP simulations to Alembic Format for rendering in 3DS-Max and Vray. The file sizes are getting up to 50 gig for one cache. I can read this file on our server  but when rendering on the farm the file sometimes becomes unstable and locks up access halting all rendering. Eventually it unlocks.

My plan is now to export an alembic file per frame so there will only be one machine accessing a file at any one time.

 

So my question is how can I export a sequence of alembic file from Houdini (export.001.abc, export.002.abc ...)? I have tried putting $F into the file name but this doesn't work, anyone got any ideas? Is it possible to change the filename with a Pre-Render Script?

 

Thanks

 

Graham

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Hey Graham, you can easily do it with Python in the Python shell, I've done this before but I don't have the script on me. I'll try to remember to post it later tonight (probably tmrw morning your time).

 

Cheers,

 

Diego

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if it's possible i would also consider the possibility to export per frame data in the scene format of your render engine, that your lighter can load as read archive directly.

- Vray -> .vrmesh

- Arnold -> .ass

- Prman -> .rib

- Maxwell -> .mxs

 

In a similar situation we ended up writting .bin data with realflow exporter and read them directly as reference in maya.

 

I say that because alembic really has this Only one mesh philosophie and using a script to hack this work but would not be the best option imo.

 

check this :

https://groups.google.com/forum/?hl=fr#!topicsearchin/alembic-discussion/one$20file$20per$20frame/alembic-discussion/xs32Rui4zR8

https://groups.google.com/forum/?hl=fr#!topicsearchin/alembic-discussion/one$20file$20per$20frame/alembic-discussion/ZLarBmKNSlo

Edited by sebkaine

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.vrmesh would be ideal, but there is no way to export this from Houdini. It is possible to convert alembic to vrmesh but this would mean an extra painful conversion step.

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my vray skills really suck but you have an utility in vray that is call ply2vrmesh

you can find it here  :

C:\Program Files\Chaos Group\V-Ray\Maya 2015 for x64\bin

 

it will allow you to convert .bgeo sequence to .vrmesh sequence

http://help.chaosgroup.com/vray/help/200R1/tools_ply2vrmesh.htm

 

At the time i need to use it there was a subtility , you have to write .bhclassic instead of .bgeo and then rename them to .bgeo to make it work because .bgeo format has change from H12 but this issue could be solve now check chaosgroup forum.

 

vrmesh is native geo and thus loading them per frame will be most efficient i think.

pay attention to export velocity for the motion blur , but i don't know exactly how it works in vray

Edited by sebkaine
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I will give the ply2vrmesh a test. I will also need to check if its able to transfer Cd and v correctly like the Alembic format does.

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just in case your in windows i give you ms-dos command to batch the process

you have to create 2 .bat files rename.bat and convert.bat

 

rename.bat >

rename myObject.????.bhclassic myObject.????.bgeo

convert.bat >

for %%T in (*.bgeo) do ply2vrmesh "%%T" "%%~nT.vrmesh"

ms-dos wins hands down the golden palm of the shitty synthax ! :)




			
				


	Edited  by sebkaine
	
	

			
		
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let me know if it works with custom attribute , i'm interested !

.vrmesh support them so i would see no objective reason that it doesn't work ...

 

and don't forget to put your smooth before export , because i'm not sure you can smooth a vrmesh.

Edited by sebkaine

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I'm trying to convert a .bgeo mesh to .vrmesh but I get an Error reading the .bgeo file: Magic number not found... 

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Have you enter the magic number ?

 

just kidding .. :)

- when you write your geo you had to export it as .bhclassic NOT as .bgeo

- then use the rename.bat to transform your .bhclassic into .bgeo

- then use convert.bat to transform your .bgeo into .vrmesh

 

have you done exactly this ?

Edited by sebkaine

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No, I just found the same info about bhclassic and gave it a try. Its all working :) I get velocity motion blur and Cd by using Vertex Color on map channel 1. Same setup I have been using with alembic.

 

Thanks for help. I will test with a sequence tonight!

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So you confirm that custom attribute are converted in the vrmesh and that you are able to read them in Maya ?

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Here are file sizes for 1 frame

 

alembic    32,724 KB

bhclassic  35,638 KB

vrmesh    14,879 KB

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let me know if all works smoothly with a big FLIP sim with support of motion blur in 3dsmax,

if it work in max it will work in maya vrmesh is not app centric.

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Yes, it should also work in Maya. I am batch converting the .bhclassic to .vrmesh, thanks! I didn't need to rename to bgeo. When its finished I will set off a render to test. I will let you know how it works out!

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So I have done a test with a 150frame FLIP simulation converted to both alembic and vrmesh. Motion blur and color Cd are working in both formats.

 

File sizes

alembic 15gig

vrmesh 6.5gig

 

Looks like vrmesh has much better compression than alembic, which is a suprise. I thought alembic would be better!

 

Also vrmesh was slightly faster at rendering. Its vrmesh for me!! :) Thanks for Help!!

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