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Nunikasi
08-18-2009, 06:25 PM
Hi.
I came up with an idea for making easy reflections on 3D objects for use in tracked shot.
Why can't I just shoot a christmas ball then use that as a reflection source? Can this be done?

I mean, are there any other ways making reflections, that also are affordable to a 14 year old? :D

Thanks in advance :D

sundialsvc4
08-18-2009, 07:16 PM
Okay, I'm trying to visualize the shot that you're talking about ... Please describe to us what your proposed shot(s) will consist of, whether they are CG or live-action and how you might thereafter be combining them. "Yes, you can do absolutely anything with CG," but it entirely depends on what you want to come away with ... the nature of the final, finished shot ...

(And for what it's worth, you bet you can use a silver Christmas-ball, hanging on a piece of monofilament fishing-line, as a reflection reference in a live shot.)

B4C
08-18-2009, 07:20 PM
You can and it has been done. Check out Zap's image based lighting demo here (http://www.zaptronic.com/). Now your only problem is getting hold of a camera that lets you shoot multiple exposures?

Nunikasi
08-18-2009, 10:33 PM
Cool demos that zap guy had. But as I understand it, the christmas ball method isn't a very flexible solution, really.
But say I want to make a shiny CG ball, and put it in a parking lot I filmed before.

Can I, like, make a HDRI "world" by taking many pictures around from where that ball will roll?
Maybe HDRI ain't a good sulotion since the reflection only will match in one point, and that is where I took the pictures, or the center of the HDR sphere..?

rendermaniac
08-18-2009, 10:36 PM
If you are shooting a christmas decoration, try to get quite a big one with the least amount of scatches. Also shoot with as long a lens as possible, so that you can fill the screen as much as possible, while standing far enough back so the reflection of the camera is as small as possible.

Then you can use HDRshop (http://www.hdrshop.com/) to convert to a normal environment map.

Simon

B4C
08-18-2009, 11:44 PM
If you want your cg element to move through the environment, you'll have to create multiple HDRI's of where your subject will move and then transition between them. I believe this (http://www.ted.com/index.php/talks/ed_ulbrich_shows_how_benjamin_button_got_his_face.html) video talks about it a little. If not, it's an inspiring video anyways for those working with IBL. I think that's what you're asking, right?

Nunikasi
08-19-2009, 06:56 AM
Yes it is what I mean :D
So now I know how I can do it, but how would I set it up?

Will see the video when I come home from school.
Thanks

jfrancis
08-19-2009, 02:07 PM
Hi.
I came up with an idea for making easy reflections on 3D objects for use in tracked shot.
Why can't I just shoot a christmas ball then use that as a reflection source? Can this be done?

I mean, are there any other ways making reflections, that also are affordable to a 14 year old? :D

Thanks in advance :D

It wasn't HDR, but that's how it all started back in '82...

http://www.debevec.org/ReflectionMapping/miller.html

Nunikasi
08-21-2009, 06:55 PM
Bump.

So does someone know what they do in the industry leading companies when they insert CG material intor real-world? How do they make the reflections look right? And theres also lighting.. Is it normal to use multiple HDR files in a scene?

RagingBull
02-24-2010, 12:19 AM
Good evening !

I had exactly the same problem, mid last year !

Unfortunately I didn't complete my test working in the same manner that you are thinking, of using multiple HDRI's in the shot. I just don't think it's how you'd do it on a real film set.

And just think that if your CG ball was rolling down a busy road, you wouldn't be able to get all of the reflections properly ! (using the HDRI in the traditional way of lighting + refl)

However, on a shot by shot basis your ambient lighting will be about right.

What I mean is that, say your scene is this:
Starts in an underground car park, then go outside in full day light.

You would be better off having 2 or more shots on the video camera edit, rather than one long continuous shot whereby it moves into changing light conditions.
At least in that way, if you had 4 cuts in the edit, you could take 4 HDRI's for the CG ball.
In that way, it doesn't need to be a perfectly smooth transition for the lighting changes.

And as for the reflections, if there are people walking around, or traffic - this is the part which I am stuck on !

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