Resimulating explosion for slow down loose fire

[jstrob]

Hi,

I'm trying to resimulate an explosion to slow it down with a 0.2 factor. I also add a bit of wavelet and 3x more resolution. But my problem is that the fire disapear very fast with the resim. In my original sim there is a huge ball of fire that lasts almost 200 frames. In the resim, it lasts only a few frame at the beginning and then we see only smoke. Should I remove the cooling or something when resimulating I thought we should not change any dynamic parameters when slowing down...?

[Ivaylo Katev]

did you enlarged the source activity five times ? the bad thing when slowing down is that you have to change the source timing as well.

[Svetlin.Nikolov]

You are using time bend resimulation, right? Is it the slow down method you're working with, or the general-purpose? The slow-down method really tends to lose fire and we have to investigate this - with general-purpose there should not be such problem, but there may be flickering instead. It's very important that you use 1 step per frame and multi-pass with slow-down time bend, though. If you already are, then it's up to us to fix it and get back to you...

[jstrob]

I didn't change the source timing... I used 1 spf, multi-pass and slow-down method.

I tried to exagerate fire in the first pass and put coolling to 0 for resim to see if I can get what I want. I will try adjusting the source timing to see.

[Svetlin.Nikolov]

Oh, indeed - if your source is animated, you should definitely stretch the animation 5 times - during time-bend resim the sources still work to produce smoke and temperature.

[jstrob]

Ok great, thank you both for your answers!

[Svetlin.Nikolov]

Please bump us if you still have any issues

[jstrob]

Ok thanks. And Just as a reference for others who would like to know how to scale the keyframes in time precisely for this situation: for example if I want to slow down my sources 5 times, I select all the keyframes and enter n*5 in the frame box at the top of the curve editor.

[Svetlin.Nikolov]

Wow, nice! Also, you can scale all of your scene's animations from the time config dialog -> 'Re-scale time', but this one looks very nice for scaling only a few objects!

[jstrob]

BTW I'm doing some personal tests of nuke explosions after studying your scenes Svetlin! thanks for those!

[Svetlin.Nikolov]

Oh nice! Eager to see the results

If you are using PCG, just in case I must warn you not to crank the quality above 100-150 - there's an issue that will be fixed in a couple of days together with some tweaks in the vorticity (yet again).
Also, if you are using a nightly from the last 3-4 days, you should have a version with a change that improves the rolling of the smoke and fire

Cheers!

[jstrob]

ok good to know! I tried a bit with PCG but I think the result was a bit too uniform so I chose direct symmetry instead (I think I was using a quality around 200) so I will try again once you fix it. I have the nightly from 2 days ago if I remember correctly.