I think the camera tracking has been one of my biggest worries during this project. It is something I have only fleeting experience with, but it is essential for producing a polished end product. When filming any moving camera shots we decided to keep them on a tripod and just pan to keep things simpler. The first shot I chose to track was probably one of the most important shots in the entire project: the very final shot where the elephant gives the monkey back to the mother.
I have been using Boujou as this was the program we were introduced to during a previous compositing project earlier in the year. It had produced a great result for me in the past, but I was aware that others on my course were not so fortunate. Boujou does not always get it right first time. I imported the footage and set Boujou to tracking the movement in the image. To do this, Boujou latches onto distinctive areas in the image (ie colour changes which suggest edges of objects). It then tracks how these points move throughout the footage. To get the best result, it is generally necessary to have points that occur on the x, y and z axis within the 3d space of the shot. However the shot I was working with had a flat wall in the background (which meant no track points in the z axis) and I worried that Boujou would struggle to know how close or far away the camera was throughout the shot. The next stage of the camera tracking was to ask Boujou to use these track points and their movement to create a camera in 3d space that matches the movement of the camera in the shot. Thankfully I found an option at this point to tell Boujou that the camera was nodal. This means Boujou knew that the camera was on a tripod and in a fixed position and could only rotate. Finally, I could export the information into Maya and check to see whether it worked. To my delight, the tracking seemed great. However, I quickly noticed that objects in the scene seemed to suddenly move up and down, or side to side out of time with the footage. Since I have no knowledge of how to correct this in Boujou I decided to see if I could fix it without too much effort in Maya. I played the animation until I found a moment when objects in the scene moved out of sync with the footage. I then checked the camera’s curves in the graph editor to check if there were any odd kinks or jumps. Most of the problems were extremely easy to find and fix, but there was one that was extremely frustrating. About two thirds of the way through the scene skipped sideways suddenly and then gently eased back into its original position. I could find nothing on any of the curves that would indicate the camera was rotating like this. I spent a long time trying to establish whether it was just one curve or all of them effecting it, but eventually, after some painstaking work tweaking each individual key, I managed to tidy it up so that the movement was barely noticeable.
I wanted to set up the scenes that my animators would be using before I did anything else, so I then moved on to some of the scenes with a fixed camera. I created a new Maya file for each one, referenced the elephant rig and created a new camera. I created an image plane for the camera with the .png sequence of the correct shot. I cannot believe how difficult it was to then actually manage to position the camera in 3d space so that it lined up with the footage. I had foolishly assumed that it would be the moving camera shots that would cause me the issues when all along it was positioning cameras by hand that would be my downfall. The situation was made more frustrating by the knowledge that I had assumed Motion Graphics were taught easy ways to work out the position of cameras in still shots. In 2nd year, we learnt to take a photo with the camera in the same position and an item in the shot that you knew the dimensions of. You could then use this item to help line up the camera. Since I was relying on the knowledge of my Motion Graphics students as I knew they had plenty more experience than me, I readily accepted their answer when they assured me nothing was needed for these shots. It was pretty galling when I asked them later on how I would be positioning the cameras and they answered “by eye”. I have at least learnt one lesson from this. Whenever possible, if filming for a VFX composition with a still camera, make sure there is something in shot that you know the exact dimensions of. It will make your life so much easier.