Jack Smyth, Car Panning Sequence, DD1410, Visual Effects 1, Jamie Scott

The Panning Shot:

 The panning shot is bringing a car from one shot and integrating it seamlessly into a background shot, this one of which is panning.

Originally, both  the car and the background shot were both panned shots, but in the end product, only the background is need to be seen to pan, so the goal in this shot is to integrate the car into a pan, therefore, the first step is to take a singular frame out of the car sequence, and then using 'trackers' to keep it in place in the background shot. If this works, the camera will pan down, and the car will stay in the exact same place in the shot throughout its entirety.

Here are the two original shots that were to be blended together to make a final product of a car integrated into the pan:

As was mentioned before, the photo you see of the first shot, is actually the singular frame that was mentioned. With using a singular frame instead of a pan, the only thing that would needed to be tracked was the background as it pans.

In the 'Car colour correction' post below, you can see how both of the shots above are close to, if not nearly identical to the foreground and the background picture of the car colour correct. This would make the majority of the preliminary work easier, as all that will be needed is to bring across the entire information except for the shots used themselves, and integrate them into this shot.

This means the car itself will have a rotoscope as well as the same colour correct and grading, the same goes for the background. The car shot however, differs from the last, and so the rotoscope had to be adjusted to fit the new additions or exclusions from this car. In this case, the boot is closed and there is no 'boot pole':

The rotoscopes used for the car are very similar, the only thing that was needed was to re-arrange the curves around the car, and delete others, such as the boot and the pole.

Since the cars rotoscope has now been re-arranged upon a singular frame, and the lifetime of the rotoscope is set to 'all' (Which means the rotoscope will run throughout all the frames of the background panning shot), all that needs doing is to bring this rotoscope into the background shot and use the trackers to fix it into place:

Once the car is in place, notice on the picture above that there is a line coming from the circular transform icon used to rotate, scale and move our object. This is the transform node being changed with the tracker, which is shown in the image below. What the tracker does is capture a point on the screen and try to stay on that point or colour until you wish to stop the tracker. Colours that stand out work the best, and in order to gain the best results from a tracker you must think about what you will be tracking.

In the screenshot above, the tracker that was used to keep the car in place was placed on the top of the green post, this meant that the tracker would end its cycle only when the tracking point went out of frame as the car pans down below the car, by this point another tracker is then used.

 

How the tracker is implemented into the transform is by bringing the tracked information (The top image) and placing it into the translate of the transform mode (Translate meaning the X and Y axes, vertical and horizontal). Once this has been done, the car itself would be off mark, so what must be done is to right click on the translates and go to 'Edit expression', then add a minus ( - ) and use the center point below (In this case for the X axis, the center point stating 764.179992). If this is successfully done for both the X and the Y, the car rotoscope should line up correctly  or close to the tracker information. In this shot, the cars transform nodes had been moved using a command key (the control key and the left mouse button held down), this means that the transform circle icon can be moved, but the car can be left in place. 

 Above is the example of how the 'Edit expression' tool is used. 

Now that the first tracker and transform have merged, the same must be done until the car itself disappears from the shot. In this sequence, three trackers have been used at different point, each having a unique colour or place that would have aided in gaining a successful track, below are the points the first two trackers were placed upon:

As mentioned before, the green post and the sky gave a good difference in colour, the 'tissue' on the ground, a white against grey, which could track well because of it's contrasting colour to the background. 

When tracking, there are two boxes, an inner and an outer box. The inner box tracks what you want tracked, whilst the outer box is the 'search zone', which will try to find a similar image throughout the track, therefore keeping the inner box in place and tracking that one point you choose:

 

The next two transforms and trackers were placed in relevant places inside the shot that would track well, in this case, the top of the post, the tissue, and a small area of grey on the ground that differed from the background as well:

Once the transform nodes and trackers had been worked together, the car would seamlessly move throughout the shot in the place the car war originally placed in, until the car is out of shot (Which is why the final tracker length seems shorter than the others, there would be unnecessary tracking if there is nothing inside the shot to be seen tracked).

This is the node tree after the final product has been placed together and connected properly:

 On the right hand side is the node tree from the 'Car colour correction' shot that features in a previous post, this is placed here to show you what has been changed the original information from the still colour correct shot. For the panning shot, transformers and trackers have been used to place the newly rotoscoped car into a background shot which pans, whilst the colour correct from a previous project have been brought in because of the car and the backgrounds similarity, this means the compositor can focus on the tracking information and if needs be, tweak the currently existing information for the colour correction at the end.