The aim of this module was for us students to gain practical
understanding and awareness of technical issues of shooting
miniatures and green screen live action using motion control
as well as bring everything together in the compositing and
grading stages.
To learn the principles and witness motion control
in action we visited The VFX Co a UK provider of motion control.
Having an understanding of the possibilities and effects which
can be achieved with MC we wrote a script for a 20 second
short film which we plan, direct , shoot and digitally composite.
Three seasons
Three seasons - Concept
A life lapse through a London street where people live, rush,
fight, sleep, party and play under marching bands of weather.
Travelling through heavy rain, hot sun and finally snow! So
this is a breezy umbrella cocktail with icing on top.
Pre-production/planning
Rather than drawing a storyboard we used two programs: Antics3D and Maya. In Maya we imported measurements of the model and reference photos and made a simple scale model of the street and action. We then used Antics 3D to allow us to quickly flesh out the camera movement and experiment with our action to get a feeling of how the timing of our action would work.
3 seasons - Animatic
The shooting of Three Seasons had to occur in two parts: firstly the miniature followed by the live action. Shooting the miniature first allowed us to match the live action footage with the model quickly with precomps and also to resolve any possible issues with the miniature loaned to us by Artem. The main issue we had to face was the original miniature curved road. If we decided to shoot a curved road we needed to be able to recreate that curve in real scale for the live action shot. Since we didn´t have the time or money to build a real scale model of the road curvature we had to flatten the road of the miniature.
Original miniature from Artem Flat version of the miniature
Miniature Shoot
Lighting the miniature Motion Control Software
The animatic camera data could have been exported to Flair (MYLO software), however as the move was simple it was decided to recreate it on the day. Basically , we moved the rig to the desired start , middle and final position , store those positions and the computer software joined these 3 points with a smooth curve.
The miniature was 1/6th scale(16ft) of a London street on which we would shoot 4 camera passes :
Practicals - Shooting the internal lights of the model with other lighting off. We can use this pass to eliminate studio reflections in the windows.
Sunlight - Lighting for a hot day
Snow- Using scaled paper snow to dress the snow pass and also shot falling snow (although the snow looked good due to the physics of scale it fell a little too slowly)
Rain- Wet the model and shot falling rain passes using back lights to highlight droplets.
Creating Snow
Praticals pass
Preparing the model to make it look more realistic in camera we ‘dirtied down’ the street, props and the buildings. We shot HD using a MYLO motion control rig provided VFX Co and operated by George Teophanous.
High Definition Camera
George Teophanous
from the VFXCo
Take 1 ... Pedro , Sambo , Rodrigo and Bjorn
Live Action Shoot
After shooting the miniature we created a rough composite of the background which was used to check against the green screen live action footage. We used onset a Reality DSP PC to record composite RGB loaded with Combustion. With this arrangment we could quickly check the live action scaled into the miniature. We noticed that with the scale any minor error of position caused large slippage of the actors on the background!
We used 2 green screens a 30x20 and an additional 20x20 at a 30degree angle to cover the space where the camera raked back down the street at the end of the move. In addition to this we painted 12 8x4 flats which conveniently could be added/removed where needed/(surplus green reflects green onto actors creating spill).
Preparing the Studio
Greenscreen and lights
We shot live action for each lighting setup and MYLO program for rain, sun and snow passes. Since the scale was 1/6th there was about 40ft of MYLO track having to cover much greater distance at higher speeds causing problems as we noticed later when putting everything together (more about that later).
Mylo in action! Mylo Motion Control Rig
We used minimal physical SFX wetting down the umbrella and newspaper for the rain action and the a snow polymer for the snow balls.
The snow pass was crazy keeping control of 3 very excited and energetic children, but we managed to catch a good pass (just!)
Post Production
This is the stage where we bleed for our shooting mistakes sweating in front of the computer!
We noticed that the live action had a relative inconsistency of motion blur over the background (live action camera was moving 6x faster than the background) coupled with a fair amount of green screen spill. Lots of Keying, Rotosscope work and colour correction using Combustion! We took it a step further however when we switched between 2D and 3D environments to find solutions to more the cantankerous problems and since we had to 3D track the background it was fun to add some 3D furniture to the scene!
Phone Box / Rain Pass Deck chair / Sun pass
The following is a quick breakdown of the more difficult shots.
Sun chair girl (Wilson)
The first key was not promising! There was spill reflected almost completely chewing the chair and the rogue was munching casually at her ankles! The sun chair did not stick to the pavement for two reasons firstly the positions were mismatched (arg!) compounded by serious camera vibration shake due the fact that we were shooting on a video camera which at high tracking speed bobbed around happily on the MYLO head unlike a 35m film camera which is much more solid.
First approach was to try to stabilise the sun girl by tracking the deck chair pre-processed boosting contrast and edges to assist the tracker. However the point tracking tools in Combustion often went west due to the motion blur and tracking quality of the image and above all we had no tracking markers on the green. Doe! I turned to Monet a planar tracker which is much more tolerant and I found myself with a reasonable track. After Monet I imported and tweaked the track in Combustion and then applied a stabilisation node to cancel x&y movement (see ya MYLO!). Using Monet again I tracked the background pavement then back into Combustion pinned Sun girl onto the pavement and rendered the results. Time to go home? Not quite...It looked okay first time, but second glance the chair shifts due to the imperfect track/stabilisation and the chair just looked mauled. I decided the sane approach was to repair bicycles or track the background and make a 3D deckchair which could be pinned solid to the background and mask the original chair placing the sun girl onto the 3D chair! Voila! A bit of grading and the adding blur the shoot finally worked! Although I think the final colour quality of the image had suffered from the green spillage!
Phone box (Rod)
Rods task was to put Cizi into the box behind the glass. First approach was to do everything in 2D taking a photo of glass and travelling masks. The render looked okay but there were flickers at the pane edges. So putting another foot into a 3D the phone box pane was tracked manually to the footage giving a clean edge. Returning to Combustion the task was to grade the sharpness of the edges to blend with the real box.
Children playing / Snow Pass Snow Final Shot
Snow children (Pedro)
The children were much too large so when scaled to the correct size they clipped the frame. So i had to find a solution to avoid this. Initially i tried to duplicate the children layer to try to mask the cllipping but it didn´t work since we had a very limited number of passes with the children and they would all look the same.
My next approach was to timewarp the children and then manually matchmove them in Combustion . This technique proved to be quite sucessfull and was improved when added CG snow on top of children.
In order to blend the snow from the miniature with the snow from the children pass i had to rotoscope the 3 kids and colour correct them so that they could look believable in that street scene . Finally , i created a 3D Ball to help the transiton from the sun to the snow.
As it may well be clear we had to practice quite a lot of skulduggery to get a working result! Although it was a lot of hard grind work it taught us not only what to remember to do the next green screen shoot to make life easier in post, but also how to think around corners and leap dead ends using 2D and 3D software in accord.
Here’s some green wisdom which rubbed off on us.
Miniature - The scale was too high, which magnified move errors x6 and caused heavy motion blur on the live action!
Camera - The ideal camera for a Mylo is a 35m film video cameras work okay, but do not fasten well to the MYLO head hence the vibration issues. 16m Film will not work at all since the film is too unstable passing the gate as it only has a single film claw.
Dealing with the motion blur inconsistencies we could have shot faster shutter, over cranked or strobe synced light.
Green screen - Our experience was that the green screen was over lit causing in some cases quite heavy spill. we have found that a key can be drawn from a much more lower lit even green.
Tracking - Placing green tape tracking marks would have saved us much time getting a decent track on green.
Floor plan - We made a 3D scale set although a proper floor plan with measurements such as camera distance and high etc. Taking as much information about the camera position, lens and focal length all helps if you need to match move.
Conclusion
This project was ripping fun! Hooray! There was a lot we learnt in this exercise and we finished with a decent result. Of course we could go on adding more bits such as snow men cars, gondolas on the Riviera. Mallard gentlemen. So much for possibility. We have the confidence to take this knowledge further onto future projects and have gained invaluable practical hands on knowledge with some brain bending problem solving.
Credits
DIRECTOR : VFX CLASS ( Pedro Pinto, Rodrigo fernandes, Sambo Gansser , Wilson Stockman )
PRODUCER : NFTS and VFX class
VFX SUPERVISOR : Chris Holmes
POST PRODUCTION
SUPERVISOR: Chris Holmes
SFX SUPERVISOR: Graham Brown and Mark Holt
POST PRODUCTION: VFX CLASS ( Pedro Pinto, Rodrigo fernandes, Wilson Stockman )
MILO OPERATOR: George Theophanous
MILO ASS'T: Jay Mallet
DOP: Bjorn Stahl Bratberg
CAM. ASS'T: Xavi Amoros
ELECTRICIAN: Rob Pye
