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arkahtek

RE-timing nuclear pyro sim help

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hi guys, i really need help in figuring out how to properly retime a cached sim. i posted before  and i got  really great help from Rbowden on how to re time a cached sim.(Thanks again Buddy) Now that i learned to retime my cached .bgeo files, i have an issue when i play back the retimed sim i get a strobing type of effect. The colors of my explosion change on every frame. This is what i did. I cached the sim out using  $FF.bgeo. I changed the substeps on the autodop network to 10. Then in the playback menu i unchecked integer frames and i set the box next to it to .10  In my pyro import network i bought in my .bgeo files into a file sop, then underneath that i dropped down a timeblend then under that a timewarp node. The original frames for the .bgeo sequence is 48 frames. I'm trying to stretch/slow it down to 480 frames. so in the timewarp node i added the original sequence of frames 1 - 48, then in the box below that i added my desired sequence of frames 1 - 480.
What am i doing wrong here? No matter what i try i get this weird jittery look when i flip book the sim or when i view it in the viewport

i added my hip file below without any retiming.

OMG PLEASE GOD, LET THIS BE THE FINAL NUKE!.hip

Edited by arkahtek

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Guest tar

turn off 'resize container' in the Dop network.

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Marty Turn of resize container in dops? Ok I'll try it and post back 

I tried it..I bypassed the resize container in dops..when I use timewarp after the time blend it still has that strobing changing colors effect. When I use a time shift after the time blend and uncheck integer frames ..I put in $FF/10 since in autodop I sub-stepped by 10 ..the colors doesn't change anymore but it looks like it's jumping frames it will play ok for 6 or maybe 10 frames then the sim seems to jump forward. I also unchecked interger frames on the global animation options and in the step box I put .10 still the same issues. I also wrote out the .bgeo files using $FF.  I'm really lost here. What is bypassing the resize container in dops supposed to do? Also am I bypassing the resize container after I cache then try to re-time?

Edited by arkahtek

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Guest tar

that's really strange as it works from the shelf tool explosion. Is there anything special in your setup? Can you try it out on a new file using the shelf tools.

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No there's nothing special in my set up at all everything is built from the shelf tools..I'll post the file that I'm using to re-time maybe you can check it out. I'll do that also and see how it works.. the retimed version is below..also when i subset before caching my sim changes a little, it looses that mushroom to the top a little  i'm really lost here.. you can see in the pyro import section/ yellow network box  I labeled pyro section, what I did exactly . If you were to cache out these frames and try both the time shift or time warp node you'll see what i'm talking about. On this .hip file the substeps in the dop network is  set to 4. On the TimeShift node i put $FF/4. And unchecked interger frames. Also in the global animation settings I unchecked interger frames and I set the steps to 0.25.

 

 

RE-TIMED OMG PLEASE GOD, LET THIS BE THE FINAL NUKE!.hip

Edited by arkahtek

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Guest tar

There's something up with that .hip. I would start a new file and extract the bits that are unique and rebuild and test as you go.

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Hey Marty I rebuilt the sim ..and it works a little better now. I set the substeps to 2 in the autodop to start with...there's slight strobing but not as bad as before, I figure if I substep it to 4 it would look a lot better.. Now the only problem I have is ...when I substep in dops  first then cache the $FF.bgeo.sc files to disk ..my sim changes. Do I have to cache with $FF.bgeo.sc first, then when I bring the files back into Houdini substep it in the autodop after, then make changes from there? I'm going to try it and see if it doesn't change the sim. But I just need to know if the rule is to substep before or after caching the files to disk 

Edited by arkahtek

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Guest tar

I'm not sure - as I don't fully understand the workflow you are using. The Cache wouldn't be able to add any more info by post setting the substeps I would have thought. 

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Well I set the substeps in dops before I cached it out. But changing the substeps in dops changes the sim. I don't get why it would change the sim. Isn't it just calculating values between frames. Its a little annoying. If you're retiming a sim and you substep I understand now that Houdini basically calculates the values in between frames so that a node like time blend can work more effeciently in blending frames. I just don't understand how substepping in dops just by 2 can change my sim so drastically. All I used was the shelf tools and key Framed  velocity, smoke volume, scale temperate etc..I have the shape of the Nuke the way I want it ..I rebuilt the nuke for a third time this time I slowed it down from the start as low as I can go with the scale parameter   .without destroying the look I'm going for. Which gets me closer to the speed of the sim I want... It's just this retime thing is busting my head. There's still slight strobing whether I substep or not. I haven't rendered out the files yet,since they're going to be huge, so I don't know if the strobing will translate in the final render thru mantra or if this is just something that is only seen in the view port and flipbook. 

Edited by arkahtek

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Guest tar
8 minutes ago, arkahtek said:

I don't get why it would change the sim. Isn't it just calculating values between frames. 

Each step works on the previous step, it doesn't calculate frame 1 then 2 and go back and fill in the details, so of course the evolution would be different.  

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Wow thank you marty ...ok I see now. Ok so yes my sim would change. It's still annoying tho :)

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you should check out qLib(just search qLib for houdini) ..  the volume retime ql did a great job for me of retiming without changing the look of the sim and with no strobing. 

Edited by craigthailand

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Craig, I have a Mac and tried to post the code into the Houdini.env but I may be doing something wrong, because it doesn't work. Do you have step by step directions on how to get it on a Mac. I downloaded the qlib and used the codes for Linux ..which is what someone from the qlib forum told me. I've never done this before so It may be an error on my part. I would love to get it in Houdini for sure

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so i downloaded the qlib files. since i couldn't  get that houdini.env thing to work i decided to use their example fie and merge my .hip file to theirs so that i can test the volume retime ql. i followed what they did in their example file and did the same with my file. When i flip book the cached sim, my sim stays on frame 1. what exactly am i supposed to be doing in the volume retime ql sop? i have it connected from a wayfare ql (where i cached the sim)  to a cache 1 to the volume retime ql to a null/OUT

 

EDIT: It seems volume retime doesn't work on pyro? Read qlib's Facebook post from 2015.. i haven't seen them talk about a fix yet or are you guys retiming pyro with no issues and its all fixed?

Screen Shot 2016-08-02 at 7.23.11 PM.png

Edited by arkahtek

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Guest tar

If qLib doesn't work it's probably best to start the debug process. Start by setting up a successful retime on a shelf tool, once you have that, then add in the more crafted elements.   We could do it for you but unfortunately most of us are too busy.

BTW cross posting to the SideFx forums is essentially posting the same people here ;)

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Lol yes I know, just trying to maximize any help I can get :)  Marty I'll give it another go..Maaaan this is driving me nuts.  

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qLib works fine with pyro. You need a velocity field and you need to animate the frame parameter at the top of the node.

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