Molotov Cocktail - tips?

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Old 10 October 2012   #1
Molotov Cocktail - tips?

Heya guys

Im in the process of creating a realistic looking molotov cocktail. I have the first stage down which is the bottle hitting the wall and shattering. And the rag on fire in the neck of the bottle.

Im going to be using Rayfire, realflow and fumefx

all I need some tips/brainstorming with is how should I simulate the liquid in the solid bottle and then the shattering bottle, should i do them as a seperate sim as the solid bottle and the fractured bottle is 2 different objects anyway.

Then getting the Fumefx sim to interact with the liquid, any tips or ideas on that.
It needs to be a fast combust using the liquid as its ignition and then burn in a small area.

any Ideas and tips are highly appreciated.
thank you
 
Old 10 October 2012   #2
Cool project Check out some reference - unless it's slow motion, you don't really see the liquid splashing, it's just busting up. So I'd start with the bottle, when it breaks, I'd cover the surrounding surfaces with particles and send that to ffx.
 
Old 10 October 2012   #3
ok, Im using using a scene that Alan did as a reference for the cocktail, problem is that the scene Alan did is a factor of 10 larger than what im working on.
I scaled it down to be real world size as I am going to be rendering it all out in mental ray and to keep with a realistic look.

What do I need to adjust to get the sim down a factor of 10. at the moment my flames are also very long when it comes to rest.

I havent started on the flame burst yet (after it hits the wall) just concentrating on the flame on the rag in the bottle at the moment
 
Old 10 October 2012   #4
Select it and write $.systemscale *= .1 in the listener
 
Old 10 October 2012   #5
isn't that the same as going to "utilities -> rescale world units"

I did that with the bottle and so forth, but i am re-creating the fumeFX sim.

should i just create the sim at the original size and when done rescale it. or can I scale it all down first and then do the sim??

its using a particle source as an emitter.

another issue is that the original scene is running at a framerate of 120FPS and i have changed it to 25. in theory could i do the sim at 120fps and then using the time scale change it to match the 25fps. Or would i just be better off doing the whole thing from the start at 25fps (which i have already kind of done)

im still not quite done because things are looking a little off, but will pt up some tests later

Last edited by Snake Eyess : 10 October 2012 at 11:36 AM.
 
Old 10 October 2012   #6
im using these as reference
https://www.youtube.com/watch?v=lfvceHUBWnU
https://www.youtube.com/watch?v=f_BAExO8ZCk
https://www.youtube.com/watch?v=RYp3O9fyfSE
 
Old 11 November 2012   #7
I have a few tests I can show... so far only for the Rag. Still gotta figure out the liquid like explosion.

assuming a particle source explosion effect will work

Last edited by Snake Eyess : 11 November 2012 at 08:13 AM.
 
Old 11 November 2012   #8
what does the "$.systemscale *= .1" command alter?
 
Old 11 November 2012   #9
It's very hard to give any advice on liquid or other things, before we see even a simple preview (or animatic from viewport) of where the camera is, how distance is the bottle, how much distance from the fire and explosion... etc.

If you can provide us preview just for the purpose of camera position, bottle and the wall (no need for the effects), I think all of us would be much easier to give you a comments on how to achieve various effects.

If you still didn't decide what your camera is showing and object basic animated, my first advice is to focus on that.

btw... nice find on those references... thanks.
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Old 11 November 2012   #10
Heres a test render of the bottle (mental ray).
this is not a final render as m working on alot still for this scene.





the background is only there as a test, it will still all be properly composited together.

I also have the bottle hitting a wall and breaking done.

If you would like, i could send you the scene that i have so far
 
Old 11 November 2012   #11
A waste of good vodka and rum if you ask me. Over here we puff out the flame and drink it.
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Old 11 November 2012   #12
couldn't agree more... thats why u down the vodka or rum and replace it with petrol... THEN light and throw :P
 
Old 11 November 2012   #13
Originally Posted by Snake Eyess: couldn't agree more... thats why u down the vodka or rum and replace it with petrol... THEN light and throw :P


Ah yes. Thanks for that, always pays to get advice from those with experience.
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Old 11 November 2012   #14
ok, working on the explosion of the bottle fuel now.
Im using another particle source with a fast burst, and then it falls down. Still tweaking the look though.

for the flames that are still burning and left over after the initial ignition, should I make another FumeFX grid? (so 3 grids to this one scene)
 
Old 11 November 2012   #15
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