Previs thoughts

Just Misc Previs thoughts from a note I had sent someone months ago.

I think previs encompasses anything that is used to get a visual sense for the final product ahead of time. The majority today is 3D but video, stills, storyboards, film snippets, etc are all possible and useful.
For Star Wars and even some pictures today existing footage (from another film or stock) is seen as a placeholder and visual guide. For Phantom Menace and other projects temp actors have been shot, sometimes against greenscreen, to block in concepts and editing ideas. For some movies such as Amelia they used videos and stills from actual locations or sets to get a sense for how the scenes will work visually.

Misc thoughts

DON’T’T CHEAT!
When working in a 3D environment it is all too easy to make a change at the director’s wish. Scaling an object, moving the camera, placing objects, etc. Usually this is done to try to make the previs as exciting and interesting as possible but these add up to real production problems.

Examples:
Fantastic Four – A major sequence was to take place at the London Eye. The previs team decided to scale the London Eye to less than ½ of its actual size to make better compositions. For months we had been looking at these and all departments were basing their planning on these only to find out that it was all fictional. Since we were to shoot the real London Eye, create accurate 3D models for the final shots as well as potential miniatures that were the correct scale this was a huge problem. We now had to have the previs scramble and redo all of the shots. By now production was in a different country and another previs team had to do the work with a different software package.

Shots moving in the tunnel varied wildly in terms of camera speed, car speed and character speed. In a simple previs it looked right but impossible to make look right if it were to be shot like that.

For Van Helsing some of previs was done in a way that couldn’t be shot. In some cases the cameras were placed in areas they couldn’t possible be or doing something that defied physics. When the production crew is half way around the world 6 months looking at a previs on a laptop and the director discovers they can’t do the shot as planned, it’s very painful for everyone involved.

You don’t want to get to a location and find that you’ll need to jackhammer the road to place the camera where the previs was ‘shot’ from’

You also don’t want to find your lead actor is now somehow supposed to be 10 feet above the ground. On the location cheats are made (actor on apple box, shooting in a different direction, etc) but everyone there knows it’s a cheat and why it’s being done. When a cheat occurs in previs the previs artist may be the only one who knows it. It’s likely the director doesn’t even know that it’s taken place.

Purpose
Determining the purpose of the previs is critical. Make sure everyone, including the director is onboard.
We just need the previs to a certain point to understand how the sequence and shots work, the approximate action and timing, etc. Yet a director can easily spends weeks ‘directing’ the ‘actors’ in the previs. “No, he should smile here and then look toward the camera”.

Previs has a tendency to become like temp tracks to the sound track. Something that the director has been looking at so long that it is the only way the director sees the shots as being. On a non-prevised show the creative team may make full use of the here and now and compose the shots to their advantage. (some feature at the location, the light at that time of day, etc) On a prevised show the director may be unwilling to consider these alternates.


Speed
It’s difficult to get a full sense for speed in a previs. In early previs a car doing a drive by might have been just a colored rectangle moving against a simple background. The director of course wants it faster, faster. If the same scene were shot for real at the original speed it would have been fast enough. All the details of the car, backgrounds and motion blur would give the sense of speed. Even with today’s rendering there’s still some visual speed discrepancies.

Accuracy
When storyboards are done everyone understands these are the basic shot designs and placeholders. It is understood that the perspective and placement of the actual location will be different in real life. One problem with 3D previs, especially the more detailed they become, is everyone thinks this is the actual shot, even if the previs was done months before the actual location was chosen.

Design
A major potential problem is a lot of previs is started before any of the key creative team is hired. It may be just the director (or even just the producer or studio executive) and a team of previs artists. The amount of visual sense the director has can varied widely and the visual sense and experience of the particular previs artist can vary widely as well. On a non-previs show the director works closely with his DP, camera operator and others (production designer, VFX supv) to determine the best compositions. This is likely also based on blocking in the actors motions. Yet the previs may well lock the creative team into design decision that were made by the director and the previs artist in a vacuum. I’ve seen shows where the stunt coordinator was told that he’s to match the action in the previs. Imagine having someone like Jackie Chan being told that some previs person has already designed all the action and action shots and that all he needs to do is get his stunt team to do it that way.

A car stunt may require a special rig be placed and the stunt coordinator may know the best camera angles to capture it but the previs artist knows nothing of this and places the camera exactly where it’s going to be a problem. The director has now grown to love this and wants the stunt team to sort it out.

The same thing has started to happen with DPs but most of them have enough clout to stop it there and do it their way. So how worthwhile is the previs if it’s totally ignored? If the VFX has been budgeted based on the previs but the director, Dp, etc ignore it completely where does that put the budget and schedule?

If the previs is done ahead of time it’s difficult to talk the producers and studios into redoing the previs so the now hired DP, production designer, etc can be involved.

Science of Magic and Illusion

Wired magazine takes a look at the science of magic. (thanks to Eric Alba http://twitter.com/alba for mentioning it)

Click the title or use the link below:
http://www.wired.com/science/discoveries/magazine/17-05/ff_neuroscienceofmagic?currentPage=all


Many people think realistic vfx are much more difficult to pull off but in fact they can be easier because as pointed out, people don't tend to focus on anything except what's in the spotlight. The audience will easily accept something as being real if it's not fixated on and if it's a common thing. You can do a matte painting of a house along a street and you can do the same thing of a very abstract haunted house centered in frame. The quality of painting, lighting and compositing could be exactly the same but the audience will readily accept and even ignore the house matte painting. It's not calling attention to itself and since they've seen plenty of house they don't bother looking it over. The haunted house, especially if it's centered in frame and the full focus of the shot, will tend to be deemed as a VFX even if it were really built on the location. It's much harder to sell the audience on this since they have to suspend disbelief.

Even harder are things like dragons and other vfx that the audience knows are not real. Their subconscious knows it's not real but they readily accept all the other non-real things in a movie (dialog, actors, sets, etc) because those 'could' all be real.

Of course there are other things that can make realistic effects easier - you have a real reference(s) to the real item. By comparing photos or video there's no discussion needed about what it should look like and how each person imagines it. You have a direct reference to copy. It may take some work technically but you know once you've duplicated the elements that make up that image the audience will likely accept it.

VES Handbook

I wanted to let everyone know that there is a Visual Effects Society handbook being written by quite a few visual effects artists, myself included. There's already a publisher involved and the plan is to release it next year.

I have a few different articles halfway done for this blog that hopefully I'll be finishing up and posting once I have more writing completed on the handbook.

Cloud Tank effect

People have been asking me to provide some of the details of the Cloud Tank so that's been on a long list of subjects. Recently I had to write up some of the notes so thought i'd post it here as well.

When I start in visual effects I was hired by Doug Trumbull as his assistant. The first day I was asked to create clouds in a liquid for a film that he had just started working on called Watch the Skies. You may remember it by the final film title, Close Encounters. They needed to create clouds and they liked the look of pouring cream in your tea or coffee.

I was given a 20 gallon aquarium and $20 of petty cash. I worked in out in a few days with additional ideas from Doug, Wayne Smith and others.

This same process was later used in a number of films and commercials. (Raiders of the Lost Ark, James and Giant Peach, ID4, etc) Actually most of these used the same exact tank as well.

I've attached a couple of primitive drawings to make it clearer. My photos are packed away deep in boxes otherwise I'd post some here. This was also covered to some extent in the Close Encounters book.

Process in a nutshell as used on Close Encounters:
2000 gallon glass tank approx 7 x 7 x 4 feet deep

Water was purified and filtered in 2 large hot tubs/wine tubs(?) 1000-2000 gallons in size.
One had rock salt added (probably close to seawater specific gravity but I can't remember the details)
The salt water was pumped in first usually to halfway mark, dependent on the shot.
Sheet of thin plastic (visqueen) was laid on top. This was longer than the tank front to back and would drape out the back of the tank.

A PVC pipe running the width of the tank was placed on top of this with a rig. Later to remove the plastic it would be pulled out and this PVC pipe was used to keep it down.
A PVC piping system that looked like a fork from above was placed just above the plastic and the fresh water was pumped in.
When done this was removed and the thin plastic sheet was removed.

Now it appeared as just a tank of water but there were two layers if you looked very carefully.
A large syringe was used with aquarium tubing to add small forced perspective clouds in the distance.
The mixed white tempera paint was injected right above the slat water layer. if it went below the tank was contaminated and would require a full redo.

Next an atomic arm was used to inject the main clouds during shooting. This allowed the operator to stand in front of the tank near the camera and as they move it around a brass tube was moving in the tank.
An electric trigger on the handle would cause the tempera paint to be injected as the arm was moved. The tube came from a pressure cooker filled with the paint.

Pressure was supplied from a compressor and an electronic valve was connected to the atomic arm trigger.
We also had a light source (with rotating colored lights) that went down this same tube as a fiber optic.

Frame rates could be under cranked or over cranked depending on the look.






Close Encounters Book

Close Encounters - BluRay

Close Encounters - DVD