Can you explain the selection and use of the "green screen" backgrounds versus the "blue screen" backgrounds. Why use one versus the other in the different shots?

Johnn Webber
Knoxville, TN

John:
Good question. There are actually a lot of factors to making the choice. The primary one is pretty simple. You want as much color difference as possible between the foreground action and the screen behind. If someone is wearing a blue suit, you want a green screen behind and vice versa. You tend not to use red behind people because there is a lot of red in human skin. Ironically "X Files" is the first movie I know of where we shot in front of a screen that had all three colors: red, green, and blue. We had green to contrast with Mulder's blue suit; we had blue behind the green glowing pods, and we had red tracking marks - an adventure in compositing.

First off I find your work exceptional. My question for you is what one motion picture in the last 10 years do think changed the movie audiences expectations about special effects for motion pictures the most?

Tracy
Scottsdale, AZ

Tracy:
Thanks for the kind words. I agree with the folks that said that the watershed films of the last ten years were Terminator 2 and Jurassic park. Kudos to Dennis Muren. T2 actually had a character that was written for the edge of what was then possible in VFX, and proved that effects could do more than just expand the world of the story, they could create a novel character with menace and energy. Jurassic park proved that VFX characters could be realistic naturalistic animals, not just other-worldly cyborgs. Since then we've had a number of films in which the principle villain, (or hero) was a visual effect. Those two paved the way.

How did you make the aliens & their ship?

T.Whitledge
M.P. CA

We used a lot of techniques depending on what you were looking at. The aliens that moved were puppets and suits made by Tom Woodruff and Alec Gillis of Amalgamated Dynamics. Some of the human bodies with aliens inside were figures molded by Howard Berman of KNB. The alien blood was a sometimes real goop (corn syrup) pumped out by Paul Lombardi's crew, and most often a complete digital creation (computer generated) by Colin Strause of Light Matters / Pixel Envy. We shot backgrounds of the inside of the cave and tracked computer generated oily surfaces wherever most creepy. The inside of the ship was part a real set, but mostly a synthetic environment created in the computer by Light Matters / Pixel Envy. Some of the shots combined between 100 and 150 computer generated elements including textures, fogs, mists, lights, and small swinging pods. The outside of the ship was a miniature about 6 feet across, built by Scott Schneider at Blue sky / VIFX. The miniature was made out of plastic, fiberglass, etched brass, aluminum etc. and was mounted on a rotator for motion control photography. Only the bottom was fully finished since that's all we saw. The ship didn't really fly but just sat there and rotated, and the camera flew by it on a computer controlled dolly.

I can't include all the techniques and talented people using them to do this question justice, but there is a good article in Cinefex Magazine (July '98) that goes into pretty good detail.

I'm wondering if there is a science to figuring out just how fast or slow a camera should be running to make a miniature explosion like the one from x-files look like its full size. Or, is it something you just mess with until it looks right.

Ron
Fresno, Ca

Ron:
Good question; the answer is both, and experience helps. Theoretically the speed goes as the reciprocal of the square root of the scale. So a model built at 1/16 scale would be shot 4 times faster (the square root of 16) than normal. So 4x 24 fps equals 96 frames per second. As a practical matter, the formula is really only a rough guide, and has to be modified by a bunch of other factors including: lens focal length, subject (e.g. explosion or falling building or fire or water), closeness to camera, dramatic effect wanted, etc. etc. etc. When we blew up the bridge in True Lies we tested for about a month to make sure the water, bridge, explosion, driving tuck, etc all looked right. We shot with 6 cameras and 4-5 different camera speeds.

Hi there. My long term goal is to be in special effects for films. What can you tell me, drawing from your life and work experience, is an essential step I need to take in order to be on the right path towards this goal. What subjects did you study in school? What is the level of education that is deemed neccesary in such an industry, or is work experience and personal talent more of a key factor? I really admire and look up to people like you who have followed their dreams, and make a living doing something they love. Any information and/or advice you could give me would be very, very helpful.

Thank you very much,

Chris Daggett
Apple Valley, MN

Hi Chris.
You didn't say whether you wanted to be on the physical / mechanical side (bullet hits, pyro, smoke etc.) or the visual side (composites, CGI, animation, etc). They're different disciplines. For mechanical/physical, it helps to study welding, machining, mech engineeering, chemistry, physics, carpentry, etc. For visual effects, all that stuff helps too, but because it deals more with imagery it helps to know about that.

Obviously computer graphics is the hottest growth area now, so that is a useful skill. Learn something about how images are assembled in the computer: modeling, lighting, animation. But don't forget that you'll be assembling images that have to fit in and look like they were really photographed as part of a "real" movie. So it helps a lot to know about film making, history of film, editing, photography, lighting, and, since we're interested in fooling people, the psychology of perception, of vision. Study art, design, painting, composition. How did the old masters fool people, move people, with just brush strokes and an intuitive understanding of what looks real. What does make something look real, look near & far, look big? If you're interested in animation, study movement, physiology, watch the nature channel.

[For more education and career information related to visual effects, please see Resources. For career profiles of computer animators, see So You Want to Be In Pixels.]

How often do you have to re-setup a special effect because something went wrong the first time (like building model destruction wasn't convicing enough)? What has been your most difficult special effect to produce so far?

Ben Cichanowicz
Lexington, KY

Ben:
When you're talking about blowing up a miniature, you want to plan and test to make sure things pretty well the first time. But we'll usually make allowance for resetting and going again. Don't forget that we try to make the destruction look worse than it really is. So some pieces may be reusable, and other parts will have been produced in quantity in preparation for additional takes. On the X files building destruction we planned for two takes of everything. Some shots looked great on take 1. One shot - the downward angle - took 4 takes because the timing of the fireball rising versus the building facade falling was so critical that the smallest error ruined the shot. Take 4 on that one was a winner, which was good because there wasn't gonna be a take 5.

It's hard to say which effect has been the hardest. But it is an unalterable rule that some shot that looks like a back breaker will turn out to be a piece of cake, and one that could not possible go wrong will nearly kill you. I do remember one shot from Volcano that had lava rushing down a tunnel toward us. It had not been orignally planned for; nothing had been shot; we had to make it up out of whole cloth and still photographs. You haven't seen ugly until you've seen a visual effects shot that ain't right yet. This one stayed not right for a long time. Then one day it started to get better, and one day the director, Mick Jackson, said it was one of his favorite shots. I told him I felt like a dyslexic child of mine had just won the Pulitzer prize.

Matt:
To what degree are directors and writers connected with the reality of effects production? James Cameron strikes me as someone who knows very well what the post production implications of his projects are, yet even he creates shots that create tremendous challange for post professionals.

Thanks,

Bob Barnshaw
Maynard, MA

Bob:
The degree of VFX knowledge varies among directors, but in general it's going up. You're right about Jim Cameron. He understands VFX because he used to work in them. That doesn't make the shots less difficult; it makes them more so, because he has the eye and the expertise to really expand the envelope. He has created characters and scenes that pushed right up against the limits of the technology, and moved them. That's where the scary fun is.

Often I get questions from writers on what we can do and what we can't. I'll generally tell them to start out assuming we can do anything. It's better not to limit the imagination initially. If it's a cool project we'll try and find a way. Man's reach must exceed his grasp or what are VFX for?