Monday, 16 January 2012

CG Elements

With the virtual environment created and the footage shot and tracked, it then came time to populate the scene with CG elements.
The over all look that I am going for with this shot is a kind of fantasy futurist vision of Bristol. So, naturally there will be flying cars and large buildings. The composition of the original shot allowed for a number CG elements to be discretely placed within the scene. Here is a small example of a few of the elements I am currently working on and how they will fit into the final shot.

The above image is a tower that I modelled a while ago, but for this project there have been a few issues with texturing which I am currently working through.

The tower is situated amongst other sky scrapers at the end of the street and into the distance.
All of these elements have been lit using the Mental Ray Physical sun and sky illumination. This gives a very realistic representation of where the sun is placed and how it illuminates the geometry. All elements are matted making the final comping job possible.

As promised, a flying car. All elements reflect the environmental geometry, with the environments primary visibility hidden.

Once all these elements were in place I did a quick playblast to check the track and how it all fit together.

Sunday, 15 January 2012

Nelson St. Rebuild

Once the shoot had taken place and we got the shot we wanted in the can, it was then onto the arduous process of post production. As the hard work had been put in during pre production, the tracking process was relatively easy. The techniques I used can be seen on one of my earlier posts, although for this particular shot I actually ended up using the Nuke X camera tracker instead of Autodesk Matchmover. For some reason Matchmover was having a hard time solving. There were a few small issues with exporting the camera track from Nuke to Maya, but luckily I happened upon a neat little python script that did a good job of exporting it for me. That particular script can be found here:

So, with the footage tracked and the camera imported into Maya, I set about the rather large job of rebuilding the Nelson street environment. As outlined in an earlier post about Environmental Rebuild, I did this in order to give realistic reflections and shadows onto any geo I placed within the scene.

Using the original footage as a guide, I built the entire area out of polygons and textured then via a combination of camera projection and textures captured during the shoot by my lovely lady Elaine.

This screen grab shows the environment visible to the camera rebuilt within Maya. The green static cameras on the walk way chart the path of the tracked camera and have been used to project frames from the original footage onto the geometry.

This screen grab is the view from the actual camera track, looking at the rebuilt and matched geometry with a mixture of projections (lo res) and textures (hi res).

One this environment was finished it was then a matter of checking the track and the geometry to ensure everything lined up okay. In order to cut down on render time, I added some metallic spheres into the scene and hid all the environmental geometry apart from in the sphere's reflection. This meant that all the computer was needing to render was the sphere's and the reflections in the spheres. Much less computationally intensive.
Once the spheres were rendered it was just a matter of importing the footage into Nuke and comping it back over the original footage.

The screen were a last minute addition within Nuke as I still had the original camera track inside of Nuke. Having the same camera in both programs really saves a lot of time.
All in all I'm pretty happy with how this came out and especially happy with the track within Nuke. Seems the Nuke tracker is far superior to Matchmover.

The Shoot

So, After much Pre-Production, location scouting and technical investigation we were finally ready to shoot. For this I called on my good friends, talented technicians and lady friend for a morning of shooting. As I planned to film on a Friday morning I called up the Bristol Film Office who advised me there just happened to be another shoot going on at the exact same time in the exact same place and that it wouldn't be possible to film at that time. I kindly thanked the lady, hung up the phone and filmed there anyway.

For the shoot I hired out a number of pieces of equipment from the media centre. The first and most important piece of kit was the camera. New to UWE this year were the additions of the Panasonic af101 film camera. These are some pretty slick camera's, shooting in HD, but the nice part is the use of different lenses.

We had the choice of using either a 14mm pancake lens standard 35mm macro lens. The choice of lens is very important in the post production process, especially when it comes to matchmoving as excessive lens distortion can be problematic in gaining a smooth track. After some tests we decided to still with the 35mm macro set to infinity. This allowed us not to worry about focus issues, both on location and in post production.

As the location test shots had demonstrated, a hand held camera was proving very difficult to track. There were a number of ways around this including a ghetto setup tripod steady cam, however as we had the use of a dolly at our disposal, we decided to go for the Key West dolly (no track).

The dolly proved very good at attaining smooth motion although some stabilization will need to be added on the final shot de-jitter some of the pan.

Ollie, Rob and myself setting up the dolly and camera.
Once all the equipment was setup up we did a number of takes, testing out lenses and varying heights of the camera. Every take that was shot was logged. Additional measurements were taken such as; camera height, from ground, use of lens and measurements of objects and architecture on location to input to matchmoving software in order to recreate the environment.

After a number of tests, this is the final shot that I settled on. This shot, although far from perfect had a smooth fluid enough motion to track and good height off the ground in order to see the geographical features.

All in all the shoot went very smoothly and we managed to get a good enough shot to manipulate in post. I feel that the location reccies and pre-production test shots were immensely valuable in order to avoid any major mistakes that may call for a re-shoot.