CGTalk - Creating effects with depth...

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Mechis

03-02-2006, 03:52 AM

Hi,

I have a general technique question about compositing. How do you create effects with depth? I've been looking at compositing apps and (as I understand it... kind of new to this so I might be wrong) found that while they support effects with planes in 3d, they do not let you do effects in 3d space (like in a regular 3d program).

For example, let's say you have footage of a person with a rocket launcher and you are looking at him from behind. In the footage, he pretends to shoot a rocket.

Now, let's say I want to add smoke for the rocket he shoots. If I were in a 3d application, I would have the particle emmiter start at location one and then move it 1000m (or whatever distance you like) away from the start.

To do the effect in a compositing application, you can't (at least I don't think you can) just move it 1000m away. So what do you do? Do you just make a particle emmiter and scale it down as time goes by... so that you can simulate the effect of the rocket moving away? Doesn't this get complicated if the rocket is supposed to curve or follows a complex motion path?

Thanks,
Mechis

jussing

03-02-2006, 07:21 AM

For real 3D effects, you use a 3D app.

In the example you mention, you would animate and render the smoke trail as a particle system in a 3D program, render it out with an alpha channel, and composite it in your compositing package.

Cheers,
- Jonas

Mechis

03-02-2006, 12:19 PM

Thanks for the response. I thought that the reason people would want to do it in compositing was b/c it would be faster to tweak the look... Although, I guess you can still do it in 3d and then tweak it in a compositing package.

Thanks,
Mechis

jussing

03-02-2006, 01:16 PM

Yes, if you download some of Digital Domain's making-of clips from their website, you can see how they render a lighting pass for particles lit with a red, green and blue light source. Then they can seperate those three color channels in composite, monochrome them, and treat them as three different light sources that they can tweak as they like. Combine that with a texture pass, depth pass, and an alpha channel, and you have lots and lots of possibilities. :)

Cheers,
- Jonas

Vympel

03-02-2006, 04:01 PM

Or you a program with 3d real capabilities like Fusion (Fusion have a good 3d particles systems),Nuke, Flame

Mechis

03-02-2006, 11:06 PM

Thanks guys. DD has certainly done some good stuff. Does anyone know of other studios that have breakdown reels? I found some great work over at Giant Killer Robots. Any others?

Thanks,
~Mechis

Dutchman

03-04-2006, 05:30 PM

<...> Does anyone know of other studios that have breakdown reels? I found some great work over at Giant Killer Robots. Any others?Yep! Sony Imageworks (http://www.imageworks.com/) has some very interesting breakdowns on there page. The ones about 'Narnia', 'Spiderman' and 'Polar Express' are the most interesting! Also you can find some interesting interviews with the creators over there. Imageworks has one of the most interesting studio websites I know! :)

Also, I recommend the VFXBlog (http://www.fxguide.com/fxblog.html) (that is hosted on FXGuide now). The article about 'Daywatch' contains some very interesting videolinks with nice and interesting breakdowns.

Have fun learning the basics of compositing! :thumbsup:
-Gijs

Mechis

03-05-2006, 12:16 AM

@Dutchman
Thanks! That's a great site.
~Mechis

Fantastic Plastic Machine

03-06-2006, 11:30 PM

Maybe I don't understand the question properly, but if you DID want to move smoke away in a compositing package, most of them seem to have a sort of 3d transform operator. AE and combustion (seemingly the two cheapest) both do. In Combustion, you just have to make sure that you are using a 3d composite as your workspace and you'll get a Z axis for your transform and in AE I think you have to create a 3d layer or something... I haven't used it for a while.

Hope that makes sense...

Ben

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