In the last part of my 3D integration VFX tutorial Itook you along on an actual shoot to discuss the things to keep in mind when filming a scene for 3D integration.
Today I will talk about how to use the 3D camera tracker in Adobe After Effects CS6 to extract camera movement information and export that information into your favourite 3D program
Using the 3D camera tracker to analyse your footage and extract camera information only makes sense if your camera is moving during the shot. If you have a locked down shot (fixed camera position) and assuming you wrote down all the information to replicate the scene in your 3D program as discussed in the last part, you do not need to use 3D camera tracking and you can move on to the next part of this tutorial
However, in the UFO scene we filmed, the camera executes a pan and a tilt up towards the sky so we will have to track our footage.
Before we get to our UFO scene, let me first show you how to use the 3D camera tracker in a normal situation. I have a scene here of me walking with my camera through a street in Melbourne.
To apply the 3D camera tracker, simply locate the '3D Camera Tracker' effect in the Effects & Presets panel and apply it to your footage layer. The tracker will immediately begin analysing your footage in the background.
The 3D camera tracker is now processing your footage frame by frame and applying 2D track points to trace the movement of distinct visual elements in the scene. Once it has completed this task, it will solve this cloud of 2D track points and their movement to reverse engineer the position and movement of the camera. It will also convert the 2D track points into 3D track points using the calculated depth information.
This can take a while depending on the resolution and length of your footage as well as the power of your computer.
While this is going on, let's have a quick look at all the parameters availale in the 3D camera tracker.
I don't find myself changing these parameters often as the tracker usually does a pretty good job all by itself. However, it's good to know what these settings are useful for in case you do get into a more tricky situation.
At the very top, the effect will show you a progress indicator to tell you how much longer you will have to wait until analysis is complete.
Below this indicator you can specify the shot type.
The next option allows you to specify which track points to show.
This will only become relevant once the 3D camera tracker has finished analysing and a number of track points is displayed on top of your footage.
You can also adjust the track point and the target size. The target size refers to the size of a visual bullseye helper that you will see when you hover your mouse over a tracked piece of footage. You will see that shortly. If you want to render the track points as part of the effect, you can check the 'Render Track Points' option.
Just above the advanced options you will find the 'Create Camera' button.
Once the 3D Camera Tracker has finished its work, this button will be enabled and you can click it to create a camera that imitates the movement of the camera used to film the footage.
Let's expand the Advanced options by clicking on the twisty (triangle) to see what goodies we have in there
First off, you can specify the solve method used to try to extract camera and depth information from the 2D track points.