What to do when you run out of memory

[ddustin]

We do vehicle crashes for the legal community.

I am working on a test where the FumeFX grid is 6500" x 1500" (165 meters x 38 meters) in size.

We keep running out of memory trying to simulate in an environment this large.

Is there a way to cheat on the size of the effect zone?
the camera can only see a limited area anyway.

Can we move the fume FX grid with the vehicle to keep the area smaller?

Thanks,
david

[cgroman]

theres no need to have a much bigger grid outside the cam view most of the time. u can rotate and move it exactly as u need it for cam view to minimize unused or unnecessary grid parts.

whatever angle, position and dimensions ur grid has, the only thing u might need is to use the gravity vector to correct the direction of gravity, if the grid is rotated.

if u move the grid (animate transformation and/or rotation) u might run into problems. we tested that before and had seriuos issues while simulation and while rendering the cache in this moving grid (certain frames were not rendered). its not recommendable.

use the cutoff script from vjeko for more effectivness:

[code]-- cut adaptive grid based on smoke, temperature and velocity threshold. don'touch fire voxels.
-- only if all values are below the threshold will the voxel be emptied

-- example: cutadaptive 0.01 100.0 1.0 emties the voxel
-- if smoke is below 0.01, temperature below 100 and abs(velocity) below 1
-- if it is not cutting enough it's the temperature probably...

fn CutAdaptive st tt vt = (
for i in 0 to (voxels-1) do (
if (GetFuelByIndex i) > 0.0 then continue -- leave fire alone
if (GetSmokeByIndex i) > st then continue
if (GetTempByIndex i) > tt then continue
v = GetVelByIndex i
if (length v) > vt then continue
-- otherwise...
SetFuelByIndex i 0.0 -- clean unburnt fuel remains (fuel

[ddustin]

Thanks for the reply,
where can I get the cut off script?

david

[cgroman]

better?

[Woody79]

i have tried this script, it works very well, but be carefull when cutting too much. I got some really weird results when i cranked it up too high!

other than that its awsome, but i'm still planning on the 64bit with oodles of ram, just help lighten the load a little!

:roll:

[ddustin]

We just tested the script over night and it worked very well.

No out of memory issues at all.

Thanks,
David

[Rif]

Sweet !

[phloog]

I've deleted the demo, and am working on a time-bound license in anticipation of buying this, but now I'm thinking it won't work for me at all.

I have a Core 2 Extreme processor, and 2Gigs of RAM. Seemingly an okay setup. When I run the tutorial files, notably the jet engine one (#3 if I recall correctly), I get out of memory errors constantly.

For the jet engine one, it crashed on Frame 20. I reloaded the recovery file, and got it to continue the simulation. It looked like it was off and running. I left and returned an hour later only to find it on Frame 23, crashing out of memory.

I am not complaining about the programming. This must be extremely intense stuff. I just can't really afford to go 64-bit and quadruple my RAM. Will this cutoff script help me, or should I just forget about FumeFX until either A) they tune it to somehow use less RAM, or B) I can afford a machine with a ton more RAM?

[Rif]

A = i dont think their is much ram improvement allowable for a CFD of this quality .. u can Always Swap on Hardrive and then run into really long Simulation times but at least get them done !!

B= This is Definitly an Important point .. I dont know how much experience u have in maya Fluids or any other CFD fluid method , but Quality\ Scale= EAT RAM !! its a given as far as i know and based on all the tests i ran ..

As for that script , This script will Totally Help ANYbody that is trying to Adapt even more the ADaptivness of the inside grid.. you should definitly try it .. ( With A salt grain , witch means be carefull not cutting 2 much or well , u wont have fluids anymore ! )

[phloog]

Here's a sort-of related question: How much of the time/effort is involved in saving the Fume simulation files to the hard drive? Not talking about RAM or paging to disk here, just the activity of saving the simulation files out.

My intent would be to maybe use a USB hard drive external to store all this background data.

Would this work well?

[Rif]

That would work yes but i wouldnt suggest unless u have a Fast Data transfert.. File Saving WILL slow Down the Sim IF ur doing Big sims and u have a Bad tranfert Speed .. When u think about it , It all make sence again 2 ( Example , u have a Big simulation that takes let say 2 gig Fxb a Frame cache .. ya its a Big sim i hehe) ..

A) if ur Saving that Output Cache File on a Raptor drive 10 000 RPM , u will see the Simulation taking X time a frame ..

B) if ur Saving that Output Cache on a Network thats really slow , u will see the simulation taking X + More time a frame , and ull probably hear the Whole office screaming about how slow the Network is Suddently ..

in This case , 2 Gig to save , on faster drive takes less time than on slower drive ( aka Usb goes on that in my mind as well) . .

cheers

[phloog]

That makes sense (it has to save and ensure it saved before moving on).

Maybe the right answer is just putting in a new and enormous internal drive that's nice and speedy.

[sitnisati]

I have a Core 2 Extreme processor, and 2Gigs of RAM. Seemingly an okay setup. When I run the tutorial files, notably the jet engine one (#3 if I recall correctly), I get out of memory errors constantly.

Hello Todd,

If you have followed tutorial #2 - a "plasma jet", then simulation should not occupy more than 5Mb of RAM. If you're getting out of RAM message in any tutorial, then most probably you have entered wrong spacing value.

As I've mentioned once - we've been developing FumeFX on dual core machines with 3Gb of RAM which was quite enough. All FumeFX animations on our web site that we did were done on such machine.

As for crashes, please send us a status window text so that we can examine what have happened. In normal circumstances, when FumeFX gets out of RAM, it will swap to disk and not crash. If anyone else is getting similar crashes, please let us know.

Thank you,

Kresimir

[phloog]

All,

Thanks for all the help. I have tracked down the issue. It WAS related simultaneously it seems to the spacing and the demo's functionality.

I THINK what was happening was that I was changing the spacing and other values, but I had Max set to AutoSave. Is it possible that each time it did an Autosave, the 'Save Disabled' nature of the demo removed all my setting changes?

Thanks...it is working, and I will be ordering it today. 5MB was about spot on.

[sitnisati]

Demo version is save disabled, which means if you try to save your scene, all parameters will be reset to their default values.
You will have to disable auto backup as well.

Regards,

Kresimir

[phloog]

Additional note for any newbies trying this...check the SIZE and Units setup when you bring in the tutorial file...I believe mine was quite large, which contributed I think to the memory issue...I was making a jet engine roughly the size of Windsor castle...with a real physical sim that led to Gigs of mem needed.