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#1 Stuart C

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Posted 23 March 2008 - 07:54 PM

Question re Visual FX.

How do I 3D composite live actors onto rough terrain? Eg, If I shoot a desert landscape with rocks and boulders as a background plate and then shoot an actor in a studio on a bluescreen with the intention of compositing him climbing over the rocks, how is this achieved?.

I have seen on "making of" docos people using bluescreen blocks to simulate tables, chairs, stairs etc to be textured later using CGI, but for surfaces that are not linear such as rocks is there a method of doing this? Building bluescreen rocks to match the plate seems incredibly time consuming and I am sure there would be issues with shadows.

Can anyone help me with this? I'm new to this area of film.

Many thanks,
Stuart

PS. I'm aware this is not specifically a Visual FX message board and is slightly off topic. If anyone can point me in the right direction for a more relevant board I'd appreciate it.
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#2 Paul Bruening

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Posted 23 March 2008 - 08:13 PM

BBC it. Get one brief, wide shot to establish the scene. Do the rest of the scene in medium and close-ups. Then, you don't even have to frame the blocks.
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#3 Scott Fritzshall

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Posted 23 March 2008 - 09:57 PM

Why not just get some rocks and have your actors climb over them? That's by far the easiest solution. If you absolutely have to do it with VFX, you're still going to need to have real objects in the shape of the fake environment whenever the actors need to interact with it. Otherwise it will look like your actors are putting their hands and feet through rocks and stuff. Or if you are given flexibility by the director, you could re-shape the landscape to be in exactly the shape of what the stuff on-set was, but that's also a ton of work.

PS: You've got to change your username to be your full name.
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#4 Benjamin_Lussier

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Posted 23 March 2008 - 10:09 PM

I agree with Scott.

YOu wont have to recreate the subtle interractions of the actor stepping on the rocks. The more live elements u can include in ur bluescreen shoot, the more convincing it will be, BUT make sure the lighting matches ur background plate...
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#5 Stuart C

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Posted 24 March 2008 - 04:43 PM

I agree with Scott.

YOu wont have to recreate the subtle interractions of the actor stepping on the rocks. The more live elements u can include in ur bluescreen shoot, the more convincing it will be, BUT make sure the lighting matches ur background plate...


Thanks for the above tips. The background plates will be shot in remote areas of Central Australia so i will have to look for a similar rock type for the studio shots close to Sydney where I'm based.

Another question, what is the method (if there is one) for compositing two jib shots? Using the above example, if i had a jib shot moving across the rocks on location in the desert and wanted to composite a second jib shot of an actor running over the rocks shot on bluescreen in a studio how is this achieved? Assuming the lens type and lighting is the same...

Thanks...

btw- will update my username shortly
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#6 Benjamin_Lussier

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Posted 24 March 2008 - 09:50 PM

:S

Oh... the only way to achieve this is with a motion control rig Im afraid. Much more expensive than a normal jib.
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#7 Phil Rhodes

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Posted 24 March 2008 - 10:31 PM

Having feet intersecting realistically with the ground on bluescreen is extremely difficult. I've seen it done well whereby they threw a couple of shovelfuls of gravel (recovered from the location itsel!) onto the green floor and it keyed out beautifully, retaining the shadows of footfalls and allowing people to leave footprints, etc.

But basically, unless you're a very good compositor, don't even bother because it will look hokey as hell.

Phil
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#8 Scott Fritzshall

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Posted 24 March 2008 - 11:56 PM

Is there a safety reason that you can't have your actor there on location climbing over the rocks? Because you're talking about hauling a jib out to the middle of Australia and flying it over these rocks; why not just have your actor actually there to do it? Something isn't adding up.
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#9 Stuart C

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Posted 25 March 2008 - 12:31 AM

Is there a safety reason that you can't have your actor there on location climbing over the rocks? Because you're talking about hauling a jib out to the middle of Australia and flying it over these rocks; why not just have your actor actually there to do it? Something isn't adding up.


The background plates will be shot all over place, in extremely remote locations up to 500km apart. The plan is to shoot the plates out there and shoot the live action in a studio. We can afford to have a small unit travelling on the road shooting the plates (5-6 people), but not a full size crew. The actor on the rocks scenario is one example of many different shots that will be in the film. If it were just the one shot, then obviously we would take the actor out there.

At this stage we may still do it all on location, but I'm weighing up the options at present. We probably can't even take rocks from the locations as a lot of the sites are in National Parks!

Thanks...
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#10 Bob Hayes

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Posted 25 March 2008 - 01:01 AM

Forget the jib shot. The two shots will be completely unmatchable.

I really like the idea of creating a practical set for the foreground. Everything from 2 meters behind your talent to the bottom of frame should be set. Then just composite the BG.

Take good lighting notes and a mirror ball on location to help match sun angle.

One thing you can do is shoot super high resolution still pictures on location and stitch them into a large plate. Then you can operate you camera on your action just pan and tilt moves to side to side dollying. With good tracking points on the green screen you could get some movement.
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#11 Markus Manninen

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Posted 04 April 2008 - 01:20 AM

Bob suggests a versatile approach. I agree. I've used this approach several times on commercials where you simply didn't have time or money to do it "the perfect way".

The biggest problem you will have is matching the look (texture and lighting) between your foreground and background.
If you keep it simple (fg set with actors against a clean green screen, and the bg as a cyc) then you can spend some serious time compositing the lighting to match (if you can try to get close on set it will be valuable). The closer to can get your fg set texture and color to match the better your shot getting it seamless. Don't skimp on the time you will spend in compositing. Nor the talent you use.
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#12 Joe Giambrone

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Posted 26 July 2008 - 07:03 PM

Based purely on what I've seen in DVD special features...

You can use a foreground rock formation and manually rig (people hold) small green screens behind the actor to key out the bg. The advantages here are easy to see. The actors are on real rocks, terrain, yet you still have the majestic bg plate you desired. The whole crew doesn't have to go to the middle of nowhere, but it looks like they did.

This is a thread the needle situation in terms of each shot's lighting and angle. It all has to be worked out beforehand so everything matches.

Good luck.
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#13 Alex de Campi

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Posted 27 July 2008 - 09:45 AM

Or you can build foreground rocks and just back-project the plates of the landscape... which essentially means you do it all in camera and can adjust your lighting in studio to make sure it all works.
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#14 Alex de Campi

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Posted 27 July 2008 - 10:02 AM

And by the way the two classic films that do this sort of shot in a lo-fi way are North By Northwest (end sequence at Mt Rushmore) and the Powell & Pressbeger film about the nuns in the Himalayas, that wasn't shot in the Himalayas but in Pinewood with back projection after the DP went out to Himalayas and took photos*... Black Narcissus?

*I might be mis remembering this story.
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