Simulation caching to file

tristan_cordeboeuf

with Andy we found the maya geo cache (the second one on cache menu) can be a good way to export a simulation and watch if there is some issu during the simulation then import your geo cache and export it as alembic 😃

vpavkov

Hi Tristan,

I used that one as well, but is there a way to write zCache file in same pass while you export geometry cache?

Cheers,
V

tristan_cordeboeuf

vpavkov I don't export the zCache, just alembic or geo cache.
But you can open the geo cache on an another scene during the simulation what you can't do with the alembic.

andy_vs

vpavkov

Thanks for sharing your workflow. Interesting about the Alembic call backs. With the geo-cache you'd probably do something like write a loop with start and end frame, and write out the zCache file and the geo-cache file per frame.

andreosadchay

Good day. I can not run the script, "zCashe" for each frame. My mistake:# Error: NameError: file <maya console> line 4: name 'mc' is not defined #. I am a novice, tell me the possible changes.

tristan_cordeboeuf

just add on top of your script

import maya.cmds as mc

andy_vs

tristan_cordeboeuf

Thanks Tristan.
Have edited my post to include the import

Unlimit

Hello @vpavkov ! I’ve been facing with the same problem. I came up with the same conclusion by trial and error, but I have a gap in my knowledge of the python scripting. I can’t write a script that unload ziva cash before record the next alembic frame . Could you share this script please?

andy_vs

Unlimit

Hey, you can paste the following code in the Per Frame Callback MEL field.

float $frame = `currentTime -q`;zCache -save ("C:/tmp/out_cache/test."+(string)$frame+".zcache");zCache -clear;

This dialog is found when you click the Alembic > Export Selection to Alembic [ ] (option box)

Tested on a simple scene just now.
Remember to change the path to something that makes sense for you

Unlimit

andy_vs Thank you so much for helping me!

Hoverwolf

Hi There I am Hossam AKA HWolf, I really like that post and it was on point, I was having the same issure with long time simulations.
So I tried the solution Andy mentioned (script) .. and I was able to export the zCache Frame 'As a sequence of frames'
but when I try to load it and run the load script Maya resimulate the file .. and I couldn't load it. I really wanna suggest the idea of combining that sequence to a zCache inside maya ('The same way Houdini works with sequence cache"
This will have a great impact on the workflow.
Also I am stuck there can't export the alembic yet from my cached files.

Edit>> I used this line float $frame = currentTime -q;zCache -save ("C:/tmp/out_cache/test."+(string)$frame+".zcache");zCache -clear;

per Frame Call Back, and I am able to Export Abc files..
But still can't load the zCache sequence

andy_vs

Hoverwolf

Hey there
When you say

Hoverwolf But still can't load the zCache sequence

What exactly are you seeing at your end -- are you seeing any errors?

Is the scene in exactly the same state as when you cached it? In other words, did you change maps/ add or remove attachments or things of that kind?

Hoverwolf I really wanna suggest the idea of combining that sequence to a zCache inside maya

Would writing caches to disk rather than RAM be helpful?

Hoverwolf

Hi andy_vs
1-When I try to load the cache using the script you provided earlier

for i in xrange(1, 10):
mc.currentTime(i)
path = 'C:/tmp/out.%04i.zCache' % i
mm.eval('zCache -load "%s";' % path )

(Using the right Path where the cache was saved, and the right start and end frames)

Maya Resimulate instead of reading the cache

2-'Would writing caches to disk rather than RAM be helpful?"
Yes it will, at some point Maya Crashes due to Ram Overloard, so It was a good idea to Cache to disk instead of ram.. I can cache long scenes with high substeps...
(In Houdini The Simulation Sequence Extension is bgeo.sc , its possible to get every frame and read the cache as a sequence.. is there any way I can combine this sequence to a single cache file, or read it.. I tried to read it but it didn't work even when I didn't change anythig in the scene.
Here

In houdini I can read those 300 frame sequence as a single cache file.. it will be great if I can Read zCache from the sequence we exported earlier.. I wanna do the same with Maya and zCache and be able to navigate the timeline like the same way zCache works.. (or Combine the sequence we exported and read it in the zCache node under the zsolver)

If there is a way to load

Hoverwolf

Forgive me If I my words are not clear. I am doing my best to explain the idea I would like to suggest 😅😅

andy_vs

Ok I believe you're moving to the frame before loading the cache file, hence simulating.

Looking at your script line by line: (hint: you can use code tags to format your scripts: https://discuss.flarum.org/d/2991-how-to-use-markdown-and-bbcodes)

 
for i in xrange(1, 10):  # looks fine
  mc.currentTime(i)  # sets the time line to the current frame. No cache loaded yet. Sim triggered.
  path = 'C:/tmp/out.%04i.zCache' % i  # that looks fine
  mm.eval('zCache -load "%s";' % path )  # now you load the cache for that frame.

You shouldn't need to walk through the timeline to load the cache. Just remove the currentTime call.
Hopefully that resolves your issue, let me know either way.

As for the other stuff 🙂

Ok, just to restate your feedback (thank you for the feedback by the way):
You'd find it useful to be able to scrub the whole timeline with all the Ziva caching data present. This is more useful than simply reviewing the Alembic cache of the simulation.
One question for you: what's the most valuable thing about having the live Ziva cache vs just the Alembic?

vpavkov

andy_vs

Hi Andy,

just my 2 cents on zcache vs alembic. For me, it's simply for debugging. If i have just alembic, and i am not happy with results, or my mesh exploded on some point, its much faster for me to use zcache to debug simulation. I can see collision, constraints, contractions, and investigate where problems accured. That's big thing for me really.
I use it all the time. That's why u starterd this thread while ago.
And once again, thanx for helping me out there 🙂
Ziva is great piece of software, but this comunity and you guys are making it even better!

Cheers,
V

Hoverwolf

andy_vs
Yeah Got it, the first line after the "for all" was the reason it triggers the simulation 😃

zCache makes it better to work realtime-like and be able to see everything, such as collisions, muscle firing etc. and navigate arround it.
the only downside was the caching to ram in long scenes.. thats why maya Crashed and I tried to find a way to export alembic or Export the zCache to disk every frame. but earlier, I wasn't able to reload that zCache saved everyfram, and I had trouble exporting my heavy simulations till I found that thread and everybody here was really helpfull.. and now I can export my simulations without any trouble, but for the debugging (my 64 Gigs of ram can't simulate the whole zCahe)...
Thanks again Everybody, such great Community

dilenshah23

Hey guys,

I am testing the python command to do the same, is the python api different from the mel api?
cmds.zCache(save=path)
This create the zCache but feels like it is saving the whole zCache in per frame zcache created.
Like the fat.951.0.zcache is the output. Using mel I don't get the 0 in the file name but the same command in python creates that 0 in file name.

Also do you guys know if there is way to pass a python variable where the path is stored to the perFrameCallbackPython expression?

If python api is causing this, I can do it in mel api no issues.

Thanks.

jamesj

dilenshah23 could you print what is in your "path" variable?
The python version of the command should behave the same as the MEL one, as Maya is doing the conversion implicitly.

If you want to save out a single frame, you will need to set the timeStart end timeEnd parameters.

-ts -timeStart <float> Start frame of cache modification (default: -infinity)
-te -timeEnd <float> End frame of cache modification (default: infinity)

Regarding passing a path to the perFrameCallbackPython - you could set a globally defined variable or pass the path into the function you are calling from the callback.

I hope this helps!
-jj

dilenshah23

jamesj Hey james, yup I figured that part out. I used a global variable to be able to pass the file path and folder structure easily around. And yes the python api works the same as MEL, I just had some quotes misplaced while I was working on it.

Thanks.

jamesj

dilenshah23 glad to hear you got it working 🙂

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