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Planning and Creating a Visual Effects Sequence

Part 1: Planning By Jon Carroll

Recently I've been working on a short film with many visual effects shots. This project required a large amount of planning and postproduction work because of the science fiction theme. For this three-part series I will be taking a specific sequence of shots and going through what was done to put them together, and hopefully pass along some of my experiences and ideas to other artists.

We shot the entire film on a Panasonic HVX-200, onto solid-state P2 cards. The cards we were using were 8GB capacity cards, and each card gives us the equivalent of 20 minutes of footage when shooting in the camera's 720P Native mode. I'll talk more about shooting with this camera in a later article- the shoot for this short film ran 18 days under all kinds of conditions. The reason I am specifically mentioning the use of this camera here is that when you're doing a shoot with extensive visual effects to create in post, you need a camera that uses 4:2:2 color sampling, and the HVX-200 is the least expensive way to shoot 4:2:2 sampled video.

One of the problems we faced almost immediately was that one week before photography commenced we lost our primary location. One sequence in the film required that the main actors be inside a building with an open door where the camera can periodically see outside. Outside the door we needed to have an open area where the actors could move, with the area beyond this immediate foreground able to be matted into a destroyed cityscape. Inside the building we needed the actors to be able to conduct their scene. After losing our initial location, we had no such place where both things could be done, so we had to shoot the interior sequence on a stage with the exterior sequence taking place at an exterior location.

Military Advisor Daniel Ruiz working out movements with actors at the location.

We had access to a door at the exterior location where the actors could move into and out of the building, but the door opened into a hallway running the length of the building so there really was not enough room to stage the main actors inside the building. It was enough to provide the illusion of them entering the building, but we couldn't shoot anything inside the doorway.

Left: Silks and shade. Right: Director Shaun Mills confers with the actors.

With lighting conditions changing throughout the day, we had to make judicious use of silks to shade the sun later in the day to make it look consistent with shots from earlier in the day. (Keep in mind, this film was shot in June and July in southern California... Overcast? What's that?)

The basics of the setup for the interior. (Done in Google Sketchup)

To approximate our exterior at our interior stage, we used an interior doorway with no door. 'Outside' of the door, we positioned a 12'x12' greenscreen on a frame where the camera could see out the doorway, and used an HMI to provide 'sunlight' coming in the 'doorway'. The rest of the stage was blacked out with duvetyn because the building needed to be a large empty darkened building.

Part of the exterior panorama.

The shaded areas in this image will be matted out and replaced.

I took a series of RAW still photos of the exterior location through the doorway which will be used to construct a panorama- this panorama will be matted to remove the undesirable elements, then projected into a 3D scene to give us the matching foreground visible out the door, with the appropriate guides for the 3D elements needed to match the foreground. The shaded areas of the illustration- the shadow of the building and the fence- are where the matte lines will be. everything beyond that will be matted out including the sky.
These three video sequences are just part of the entire sequence taking place at this split location but enable you to see the application of the problems on set:

Interior sequence with visible greenscreen

Exterior sequence looking out doorway at exterior location

Reverse exterior sequence

Of course, the interior shot will be the most difficult, primarily because the camera must be tracked for the entire shot and the 'out the door' perspective must be matched. Note that these shots have not undergone color correction yet. Color correction will go a long way toward establishing them being in the same location. In the shot looking out the door, we erected a greenscreen behind the actors to isolate them against the background.

Once again, because the entire background is being replaced, we didn't want to have to rotoscope them against the background. Even the reverse exterior is an effects shot as the building is being extended to three stories tall. In the reverse, the area inside the building is blackened with duvetyn so that it looks just as dark as the interior footage. We have photo reference for the building side to be able to build the extension for the building, which will likely be modeled using a photographic modeling application. Each shot in this part of the sequence creates a separate set of challenges, but by planning a common solution for the entire sequence of the film we have what we need to be able to pull the entire sequence together.

The other part of the planning involves assessing the assets necessary to complete the shot. Obviously, the interior and exterior footage assets have been shot. The exterior extensions- namely, the 3D buildings and foreground, remain to be built. Asset tracking remains a difficult prospect, and on this short film our effects artists are professionals working at home in their spare time. Asset management and specific effects techniques will be included in the second installment.

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Jon K. Carroll is a effects artist living and working in Los Angeles and a recent graduate of Columbia College Hollywood. He can be reached via email at draven@infinite-elements.com
Related Keywords:visual effects, Visual Effects Sequence, filmmaking,


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