great ball of fire

epsilonbass

epsilonbass

Active member
So in my upcoming short that i am working on, i plan on having a scene where a sack is thrown through a window, i hope for the sack to be on fire, and to smash through a window. Now, obviously this seems very dangerous to do. I go to school where i am friends with some good 3d animators. In your experiences would it be worth doing cgi glass shatter, or cgi flames, or both? I am also thinking about the possibities of trying to shoot a scaled down verison and edit it too look real.

Any ideas? I am still in very early stages of production, so i have months to plan this out and get it right.
 
A few things to keep in mind...one, fire doesn't scale very well. So, if you go that route, test, test, test. The best way to do this would be a mix of techniques, some 3d some live.

Here is how I would do it, not knowing how you plan on setting up the shot:

1. Remove the window from the actual sill. This way there is no window in the frame and no glass to break.
2. Get a dSLR and lock it off in approx same angle as camera, buy a garden gazing ball from Wal Mart and set it in the sill and take 7-10 pics of it of varying exposures, under and over. These will be merged for your HDRi in post.
3. Take lots of reference stills with your dSLR after your get the gazing ball.
4. Film double the length of the shot with nothing there, with and without the window in. These are going to be your clean plates.
5. Film your shot, light the sack on fire if you can and throw it out the window. Make sure you ahve safety precatuions well thought out.
6. If you can't light it on fire, throw it out without fire, but shoot two passes, one with a replica sack spraypainted black with a multiple large orange dots that the camera can always see one, this is for motion tracking.
7. If you do step 6, get a sack against a black background and film it on fire, preferrably throwing it with a black background.
8. Get your 3d guys to model the window and the glass breaking that matches your live action of the sack being thrown out.
9. Composite it all together...combine your clean plates (for clean up purposes) with the CG elements, with the whichever fire sack you do, step 5 or 7, and if you use step 7 you have to track in the sack filmed against the black background with an add mode.

Voila you're done!
 
You need:

Sack
Brick
Window
Lighter

Light the brick filled sack and throw it through the window. CG will look BAD, VERY BAD. Make sure everyone is clear and that the sack thrower is wearing leather gloves.

I know somone will say that that's stupid and dangerous, but I don't really care.
 
I agree with you fully, however the problem is, that the sack is actually supposed to be filled with a dog, im supposing something around the normal retriever sized. So yeah if it was just something small i would be ready to chuck it through, but something thats gonna be big to pick up, throw, and put out, that's a lot harder.
 
. CG will look BAD said:
Agree 100%
CG will look terrible unless they guys at ILM do it.
Its stupid and dangerous but its the way i would do it.
Make candy glass to be safer!
Click to expand...
 
epsilonbass said:
I agree with you fully, however the problem is, that the sack is actually supposed to be filled with a dog, im supposing something around the normal retriever sized. So yeah if it was just something small i would be ready to chuck it through, but something thats gonna be big to pick up, throw, and put out, that's a lot harder.
Click to expand...

This might seem kind of obvious, but I'd use a cheap stuffed animal about the size of the dog. You can weight it down if you need (take part of the stuffing out of the dog, fill it with sand/beans/something with weight and sew it back up.)

And I do agree, CGI will just look weird and/or fake. Just be careful and make sure you have as few people on set as are necessary. Good luck!
 
First of, I would advise you not to do what some are suggesting. So many things could go wrong and fire can be very unforgiving. Even if you had the good fortune of not burning down the building, you could still be arrested for attempted arson.

Keep in mind that filmmaking is a process of telling a story. Just as I'm sure you're not going to have a real dog in that bag when it's thrown, you can do this sequence without breaking a window with a "great ball of fire" (a "flaming doggie bag"???).

One way to do this would be to tether the prop with black wire, where it's pulled up short of the window. The prop is then thrown and right before it reaches the end of the tether, you cut to (say) a passerby on the street who hears and reacts to sound of shattering glass in the distance. Cut back to the broken window with flickering reddish light within.

If you plan on lighting the prop before throwing it, you'll need a fire permit from your local fire department, a licensed pyrotechnics expert on scene, insurance to cover the stunt and a most unusual location release to do this wisely. Otherwise, see what your CGI friends can come up with for you.
 
Sound advice 5i's.

I would suggest all the safety precautions; no movie is worth someone getting hurt. With as much time as you have, why not just build an identicle set. This allows you to use real fire as long as you have the permits and the safety personel.
 
myswtghst said:
This might seem kind of obvious, but I'd use a cheap stuffed animal about the size of the dog. You can weight it down if you need (take part of the stuffing out of the dog, fill it with sand/beans/something with weight and sew it back up.)

And I do agree, CGI will just look weird and/or fake. Just be careful and make sure you have as few people on set as are necessary. Good luck!
Click to expand...

Don't forget safety goggles for everyone on set, long sleeves .... and two guys standing by with fire extinguishers.. (even the $8 Wal-Mart ones).

Good luck!

If you need it, I have a dog that has done some stunt work? And he works for kibble!

*joking, don't sic the SPCA on me*
 
epsilonbass said:
I agree with you fully, however the problem is, that the sack is actually supposed to be filled with a dog, im supposing something around the normal retriever sized. So yeah if it was just something small i would be ready to chuck it through, but something thats gonna be big to pick up, throw, and put out, that's a lot harder.
Click to expand...

Um...if it's too big to pick up and throw out a window....how can the script call for it?

You don't want the audience to be sitting there saying No way.
 
If you decide to use the stuffed animal, and I wouldn't. you should get a second one and test it in the open as to it's being flammable. I will bet that anything like that will go up pretty quick. I would also use a chemical treatment called c-24. You can get it from Roger George in L.A. We use it to treat clothing and other materials that are going to be on fire. I would treat the burlap as well, that way you can re-use the bag a few times. The only thing that should burn would be the accelerant.
 
Hey guys,

Thanks for all the advice and information. I am definitely not depending on the actual stunt to be the sole focus of the scene. I know there are great risks involved, and so was hoping for the fastest of shots invovled.

My flow for the scene i am seeing as such:
A man and his girl friend enjoying an evening alone.
Another man turns off, then steps out of, a truck.
The couple start to become more friendly with each other.
Outside Man drags over a larg bag.
The couple continues with their moment.
O/s Man poors liquid over bag.
Couple 8====D ({I}) (hahaha)
O/s Man drops match
Couple again
The shot of bag smashing through the window.
Couples reaction with big burning sack infront of them.
Cut to couple out front of house w/ fire fighters.

I'm definitely not depending on the shot it self to be as strong as the moments leading up to it. I don't actually plan on showing said dog, but it gets infered with the firefighters. To the same effect of cutting away i thought a brief CGI moment, or miniture shot might do the trick as the audience is expecting what's to come.

And sorry for not checking back on this post earlier, when i first made it it seemed after the inital response the thread died.
 
Just a question. What is the motivation for the bag to go through the window? It seems kind of superfluous at that point. Why bother? Again, just a question.
 
From that shot list, you don't even need to actually "do" anything.

SOUND of breaking glass
Burning bag lands in front of the couple

Probably even better that way.
 
You must log in or register to reply here.
Back
Top