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asomma
08-11-2007, 02:27 PM
Hi everybody!

Im trying to recreate the heatwave effect of a nuclear blast using Particle Flow.
Its impossible to explain, so im just gonna show you this video

http://www.youtube.com/watch?v=TfsWBgfpznk

The effect im after is what you see happening to the bus, the car and the tent at
00:32 - 00:44 in the video. As the heatwave hits the bus, the surface instantly turns to ash.

Ive tried a few approaches but im not getting what i want.
One of them was to have the heatwave particles frome the blast collide with objects, spawn to engulf the surface and spawn to emit smoke...

The hard thing is to get the direction and to get the particles flowing along the surfaces like in the video.

Im thinking maybe it would be best not trying to make all the effects of the heatwave at once but instead compositing them together (The wave itself, the turning to ash, the smoke).


How would you have done it?

Wicked
08-11-2007, 03:00 PM
I think I would let spawn particles from those objects (ie bus, truck) and use animated spacewarps: drag, wind and grav. This in combination with AfterBurn and some post-production should give you a similar result..

Offcourse, this is just theory :).

Maybe (just maybe) IŽll try to make a test..

entrancea
08-11-2007, 03:20 PM
Hmmm....I would have used another particle system where I would add a position object and add the Truck to it and and then add an Collision Test to it and set its parameter to 'Continue'.I would have set the birth to start and end at 0 thus revealing all the particles on the truck.

Now that we have got that done we add a Deflector(The one which looks like a Plane and which is termed as the deflector) and place it sideways to the truck or as you would like it.The purpose being is to animate the deflector in accordance to the Blast...so that when the heatwave hits the truck and passes it the deflector would pass through the truck at the same time.

Now wire this Collision Test to another event and add a wind force and add a wind to the scene and add a delete by age operator also.Now you can adjust the wind parameters and see what effect you like.This I guess would do as your initial setup.

If you want the Particles to emit from certain points of the truck then you can add a density(like black and white) material to the truck and on the Position Object parameter set the density by material on....

I hope this would help you...try and let me know if it works or I'll have to do the effct myself and see what comes up ;)

Regards,
Subhro

asomma
08-11-2007, 05:02 PM
THANX! :)

Im testing your suggestion now, entrancea, and it seems this will be very good to get the "bus turning to ash as the wave hits" - effect.

I've added a collision in the second event so that the smoke doesnt go through the object, but then the particles on the side that faces the wind stays there too long. Im now trying to add additional winds to make the particles move away from that surface, but its not giving me the effect i want.

entrancea
08-11-2007, 05:21 PM
Allright....nice work dude, :thumbsup:

Now lets talk business,what I guess you could do is add a udeflector to the scene and add the truck to it and add another collision in the second event saying that the particles will collide with the truck if they come in contact with it.This is just for a little for natural effect.Add a drag force to the scene and keep the wind speed and turbulance,frequency a bit high so that they fly off fast in the begining but quickly slow down with the help of the drag force,but still going off the truck with turbulance and all.....Try to set the deflection speed of the truck U-Deflector a bit low so that the particles do fly off,but not as much as sky high....you could try to play around with chaos and all just to add a bit of randomness to it all....see if all these work.

Regards,
Sub_bro

asomma
08-11-2007, 05:28 PM
The problem with the wind in 3dmax is that it doesnt flow along the surfaces of objects.

I want the smoke to behave more like this:
http://www.audiworld.com/news/99/wind/header.jpg


When I use collision to change the direction of the smoke, the smoke just continues in the new direction given by the angle of the face it collides with. Even with adding the wind to the second event the particles never flow along the object like in the picture above, instead they just spread out.

entrancea
08-11-2007, 05:36 PM
Well then for this I guess you can use the speed by icon operator.....It will allow you to move the particles the way you want them to...but you have to keyframe it then.....then u'll be able to control the path as well as get them to collide with th truck.....see if this works...


Regards,
Sub_bro

Wicked
08-11-2007, 05:50 PM
The problem with the wind in 3dmax is that it doesnt flow along the surfaces of objects.

I want the smoke to behave more like this:
[...]


When I use collision to change the direction of the smoke, the smoke just continues in the new direction given by the angle of the face it collides with. Even with adding the wind to the second event the particles never flow along the object like in the picture above, instead they just spread out.

I suggest you use an spherical wind-spacewarp with a negative value. This way you can "pull" the particles any way you want to.

Again: if you watch the video closely, it looks like the dust (ash?) suddenly appears on the bus itself. That's why I suggest you use an PositionObject to spawn the particles from the bus.

jigu
08-11-2007, 05:57 PM
I hope this is what you are looking for. check the attachment.

http://img161.imageshack.us/img161/6679/wavestm6.jpg

entrancea
08-11-2007, 06:55 PM
Ofcourse,You ticked Parallel to Surface Right?Right?

asomma
08-11-2007, 07:50 PM
:) ok, so its starting to look pretty good now

For most of it I've used Entrancea's approach, because i want the smoke to "peel off" like in the video. Once the deflector collides with the particles they get effected by the wind & turbulence.

Im using an Udeflector to avoid getting the particles to go through the bus, and im using a 3rd collision test and a deflector to delete the particles as they fly off the bus.

To get the particles flowing along the shape Im using one linear drag to keep the particles from flying off, and a spherical drag to make them wrap around the backside. I still feel that some of the particles stay on the "front" too long tho.



if you watch the video closely, it looks like the dust (ash?) suddenly appears on the bus itself. That's why I suggest you use an PositionObject to spawn the particles from the bus.As Wicked points out; all the dust in the movie appears at once...however it still clears off gradually, starting with the side facing the blast.


Ofcourse,You ticked Parallel to Surface Right?Right?Where can i find that? (or are you just messing with me?)

asomma
08-11-2007, 07:56 PM
Here is my result so far. Please play around with it and post what you get

http://www.helmet.no/alex/heatwave2.max

:)

entrancea
08-11-2007, 08:01 PM
Ha ha....No Dude,I am not messing with you....You can use parallel to surface if you use the speed by surface operator.....Can try it out and see if that helps out....I mean to say you could play around with these operators a bit to get some uniqueness to your scene....


Regards,
Subhro

asomma
08-11-2007, 08:19 PM
thanx! im gonna check that one out tomorrow, cant sit any longer infront of this computer :)

entrancea
08-11-2007, 08:21 PM
Yeah...I saw the file.....looks really good......maybe have to pull the speed a bit down.....I'll be playing around with it and see what I get!

entrancea
08-11-2007, 08:24 PM
Allright man....rest ur eyes....Goodnight....

asomma
08-12-2007, 11:45 PM
Hi,

I totally forgot we were shooting the explosion scene for the video this effect will go into today (which by the way was awesome!), so I didnt have any time to work with it.

What about you? Did you mess around a bit? :)

entrancea
08-13-2007, 07:00 AM
:thumbsup: Allright.....Well I did mess around a bit but didn't get to change much of anything....played around a bit with the parameters and added a ground to see how the dust would react with the ground.So check the file please.....

http://download.yousendit.com/44FAF8406B5DCD62 (http://download.yousendit.com/44FAF8406B5DCD62)

Regards,
Subhro

PsychoSilence
08-13-2007, 11:24 AM
any chance to get the maxfiles for max8? :sad:

kind regards,
anselm

entrancea
08-13-2007, 12:15 PM
Ummmmm......I dont know dude!I only have the max 9 version and the file was originally done in Max 9 cause when I first downloaded it....It wouldn't open in my Max 8!:shrug:

Regards,
Subhro

asomma
08-13-2007, 02:29 PM
entrancea,
I checked your file, and it looks great :thumbsup:
I had to speed down the turbulence frequency tho, since is was too jumpy for my taste... want the wind to change directions slowly.

Im will be checking what the differences are between yours and mine tonight. Maybe you could tell me a bit more about what you changed and why?



Anyways, my next problem is to get the shockwave right; I want dust to fly off the ground as the wave travels out (like an expanding circle of dust).
I've tried using the Pbomb force, but it seems to effect all particles at once.

The Pbomb does not make a shockwave that travels out from the center, but instead immediately sends all particles away from it, no matter the distance from the center. The only way i can make them form a wave is to tweak the decay
I dont want the wave to decay, I want it to travel like ripples if you drop a ball in a pool of water. As the ripple travels out it kicks up dust from the ground and turns all surfaces to ash. (nuke heatwave)



any ideas?

entrancea
08-13-2007, 02:52 PM
Thanks a lot man....but all in all.....nothing much have I changed so....it's almost the same.....and regarding that shockwave.....Hold on to that thought :bounce: ......I'll send you a file tonight and I'll tell you how to do a shockwave....It will be only done with a ground,a Pflow emitter and a speed mark operator.....Thats all....

Cheers, :thumbsup:

Subhro

entrancea
08-13-2007, 02:54 PM
Do you use Afterburn?

entrancea
08-13-2007, 03:46 PM
Allright,check this file...this is just an simple shockwave to get you started.

http://files-upload.com/files/432022/Smoke_Shockwave.max

entrancea
08-13-2007, 04:41 PM
For the dust rising from the ground....you can use almost the same process as the truck.....You can make all the particles originate from the ground and set a wind force and make them fly from the ground over time.....use afterburn shaders for desired smoke effect...you can see a sample of smoke going off from the ground from my site...Its not actually a real site but more of a place to upload some of my experiments....

http://www.cgdiary.org/rivo_viro

entrancea
08-13-2007, 04:46 PM
As for what I did for the Max file of the truck I gave you...I just added a ground deflector to make the particles bounce off the ground as that is what should happen and I just played around with the parameters a bit but nothing other than these were added....

feldy
08-13-2007, 06:11 PM
look at this video around 1:40 you will see what your looking for.

http://www.youtube.com/watch?v=JljSUt-ufZI

JohnnyRandom
08-13-2007, 07:40 PM
Anyways, my next problem is to get the shockwave right; I want dust to fly off the ground as the wave travels out (like an expanding circle of dust).
I've tried using the Pbomb force, but it seems to effect all particles at once.

Just a thought, new flow, emit from a animated torus linked to afterburn.

EDIT: Better yet this is a great excuse to buy fume... link the object source/torus to fume instead :D

asomma
08-14-2007, 08:12 AM
Thanx for all the replies! :) Im at school now, but I will check all this out once i come home.

depleteD
08-14-2007, 05:45 PM
The key to an effect like this is the details and the understanding of the physics behind whats happening.

Nuke light his the objects and they ignite, i recommend a fume object emitter with a high wind. Or particles with noise drag and follow curve animations. Box 3 can also be used to get really nice flows around objects by offseting the position of the particles based on distance to the surface or geometry inclusion.

Then the shockwave :bounce:

just add details, a couple of afterburn systems, and lots and lots of debris. Debris of the glass, the metal, the wood, and anyother materials you can think of, stone maybe...do a morph target for your geometry and crumple it. Smoke, everywhere doing lots of things.
About 10-15 different 'effects'. Put in a lot of different things to stimulate your viewers eye, so they can't focus on just one thing.

Hope this helps and good luck. :)

Post some animations!

asomma
08-15-2007, 02:00 AM
So...
We've made a few changes to how the explosion in the video should look, and decided that it would be more effectful if the blast came before the heatwave. Originally we wanted to have the heatwave turning all to dust before the explosion, but now there will be an explosion with a heatwave followed by static and then when the picture returns you will see the devastating effects of the explosion. This way we have more time to show the main CG shot, instead of just 10 frames :)

Here's a concept sketch I just made in photoshop for the CG shot (after the explosion)

http://www.helmet.no/alex/conceptsmall.jpg


In addition to the heatwave, I will be using the particle system I've created, with help from you guys - especially entrancea, for the fog/smoke/ash/fire flowing on the ground and around/over objects.

If i get permission I will post some footage of the actual explosion we shot later, which should be great for reference.

entrancea
08-16-2007, 07:22 AM
Thanks for the vote of confidence Asomma :) .....The concept art looks really good....although I was wondering like wouldn't the sky turn very dark with all the smoke and dust and debri?Then the lamp-posts would still be burning and half broken or so......Just a few questions that popped up in my mind :p ...

Chaow,
Subhro

asomma
08-16-2007, 07:47 AM
The smoke and debris in the sky will be added from the real explosion we shot on location.
About the lamp-post or powerline - whats it called? - I was thinking of having the wires hanging, most of the post turned black (coal), but i dont wanna set it on fire because we want to make the viewer see the box in the middle, the box is what causes the explosion :eek:

Im thinking about adding some water ripples under the box.

im gonna be posting a video of the real explosion soon so stay tuned!

entrancea
08-16-2007, 08:58 AM
Alright...that sounds great...will be waiting to see the actual footage....

Chaow,
Subhro

JohnnyRandom
08-17-2007, 10:03 PM
Good excuse to burn up some free time. Really pretty quick smash at it (ie quick fume sim)

http://www.4rand.com/TEST/dustwave.gif

PsychoSilence
08-17-2007, 10:26 PM
Good excuse to burn up some free time. Really pretty quick smash at it (ie quick fume sim)

http://www.4rand.com/TEST/dustwave.gif

ani info about the setup? ;)

JohnnyRandom
08-17-2007, 11:06 PM
Sure, super simple flow, particles birthed from an animated torus linked to a particle source in fume (smoke only). Rerendered the the particle flow in krakatoa (demo) for a quick debris pass. comped in fusion.

entrancea
08-18-2007, 03:05 AM
Whoa!Looks great.....

PsychoSilence
08-18-2007, 09:45 AM
thanks Johnny :)

yeah, sometimes the simply stuff is the best :D

kind regards,
anselm

asomma
08-18-2007, 11:35 AM
nice setup :)

could you show the clean fumefx animation
and the clean krakatoa animation seperately?

will the fumefx smoke flow around the teapot even if the particles go through it?
(since you added the teapot as an object in fumefx...)

asomma
08-18-2007, 11:53 AM
So here is the first of the two explosion we shot on location.
Here we blow up a campingvogn (what do you call these english?) with about 5 kilos of dynamite. enjoy :)

5 kilo explosion (http://www.helmet.no/campblowsmall.mov)


This is nothing tho... in the second shot, we blow up the ground with 30 kg! :scream:

JohnnyRandom
08-18-2007, 07:20 PM
Anselm, I started with a way more complex approach (multiple deflectors, forces, collision tests), but due to my serious lack of patience waiting for pflow to update and playing during breaks from work, I opted to cheat it out in post, it's so much faster. Even though to have it truly correct is very satisfying, I am not getting paid to do it:D

Great explosion, asomma! I love seeing real pyros go off:D Nice footage, I like how you can see the detonators spark, explode, and rumble the trailer before the actual dynamite goes off!

The shots are on my workstation and I won't have access again till monday (I'll post them then) To answer your question the Fume sim does flow around the teapot. Although not as acurately as it is driven by the particles in the flow and they do go through the teapot (again due to my impatience with pflow's single threadedness)

EDIT:
Just the dustcloud, teapot and ground plane.
http://www.youtube.com/watch?v=iki2LycwpGI

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