Post Magazine

August 2013

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dear vfx artist An on-set VFX supervisor's duties Dear VFX Supervisor, By David Blumenfeld Head of CG/ On-Set VFX Supervisor Brickyard VFX Santa Monica Some common on-set tasks. 48 Can you explain the various tasks an on-set visual effects supervisor performs during a shoot for a commercial that requires CG in post? Nearly all television commercials today require anywhere from a fair to an extensive amount of post visual effects, and a large portion of this work is done as computer generated 3D. In these cases, an on-set visual effects supervisor is required during the shoot, and they need to be highly involved with numerous aspects of the production itself. Often, the director, agency and production crew wonders what it is we are up to on-set. The following is a breakdown of the common tasks we perform, all while trying to remain as inconspicuous and efficient as possible. Detailed Script Notes: Becoming quick friends with the script supervisor is important to us because this information is helpful for creating things that were not actually shot. Camera information, including focal length, height, angle and distance from subject are time savers when recreating a virtual set or adding digital elements. Clean Plates: Often, we'll ask that a clean plate be shot for any set-up requiring post work, especially those where paint-out might be required. This is where performers and moving items are cleared from view, and the camera rolls for a few frames. These clean plates are used to allow shot items to be easily removed, including rigging as well as portions of the set. Set Measurements: Usually between takes or set-ups, we'll jump in with a tape measure or laser distance finder and record the size of walls, furniture, props, actors, or anything else of use. This is helpful when trying to digitally recreate the set. HDRs: In years gone by, this was done by photographing a chrome ball at the center of action in a given set-up. Today, this is done using a high resolution DSLR camera and a 180-degree fish-eye lens. With all the lighting in place and powered up just as the shot was recorded, the set is cleared of people (or at the very least everyone holds still), and a minimum of three angles are shot with multiple exposures. This allows us to capture the entire set as a sphere, along with complete light source information. These shots are then stitched together into a single high dynamic range image. This is both for reflections and to recreate accurate lighting to match the plate.While this only takes a Post • August 2013 minute or two to shoot for each set-up, it typically causes the most interruption, as it momentarily stops production. Lens Grids: In situations where CG items need to interact with objects in the plate, we may ask for a few frames of a lens grid. This grid, typically a large checkerboard, visually represents the distortion of the lens and allows us to unwarp it (and subsequently the plates) in post so that parallel lines are actually straight. It is important that the checkerboard be shot so it extends completely past the edge of frame, and that the script notes (or a tion, it is important that they provide proper coverage of actors, especially for things like flowing hair or other small details. These screens need to be properly lit and as free from shadows, wrinkles and discoloration as possible. We may request that the shot be underexposed by a stop, depending on the lighting, in order to obtain a better key. 3D Scans: Sometimes, it is necessary for props or actors to be 3D scanned using special equipment. While this can often be done at a different time or location, there are occasions when it is better obtained on-set, such Shooting an HDR panorama on the set of a job at Raleigh Studios. small piece of tape on the grid) reflect the lens that was used. Reference Photography: You may find us walking around, shooting pictures of walls, set pieces, props, performers and anything else of interest. Often, this is for lighting reference, while other times we may be acquiring textures. We also use these pictures to obtain better information about how the set is laid out, where the camera was located, and occasionally, for behind-the-scenes footage for making-of articles. Tracking Markers: In shoots where greenscreens (or blue-, black-, or red-) are used, we'll often jump in and place small markers. Sometimes these are various angular shaped stickers on the screen itself, but occasionally we need to place these on performers and props too. Additionally, we may place small colored balls, LED lights, or cards on c-stands at different depths to obtain better parallax. Greenscreens: While these shots are known beforehand and set up by the produc- as when actor availability or costume requirements make it necessary. This process is performed in order to digitally recreate an exact replica of the item or person being scanned. Motion Capture: While more rare, there are times when 3D motion capture must be recorded at the same time as the live-action shoot, so that the digital performance matches up with what is on the plate. This is often needed when sections of a live actor or animal are to be replaced digitally, such as with an android, or if they will be wearing a CG suit of some sort. While this list is not exhaustive, it does cover the most common tasks that need to be performed. As with everyone else involved in the production, the goal of the VFX process is the same. We all want to visually tell the best story possible with the least amount of aggravation and make everyone happy with the final product, using the least amount of budget and time necessary to get there. And all while having a bit of fun!

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