After Effects [Session 4]

Today's After Effects session was focused on learning how to use its 3D features.  

Firstly, we opened a document in the 3D view and practiced moving the camera and how to manipulate individual objects. This document consisted of a pair of clouds, a sun, some lightning, a few birds and rain. This document had flat layers, but in a 3D view, we were able to move objects in all directions, even moving them backwards and forwards along the Z axis.

We then opened another document with a few elements that had to be combined.  The tutor showed an example document that already contained a few resources, e.g. a painting and the back of a woman’s head.  This was to create a sense of depth and entitled “depth of field” whereby any object in front would be blurred.  Another feature used was aperture which controls how harsh the blurring is on objects that are not in focus. 

The next half of the session was focused on 3D motion tracking.  To do this we were given a small piece of footage of a woman walking down a street.  To test the motion tracking out, we tried replacing one of the posters on the walls with something else.  We were provided with a replacement poster we could use for the exercise.  This process was quite interesting as we used a special tool to first analyse the image and create markers.  The markers enabled you to create a solid (3D object)  that could go on top of the image and match the perspective.  There were some areas that needed adjustments.  

Because the solid started as a solid colour (pink), we then had to replace that texture with the poster selected.  Two ways of doing this were demonstrated. The first was to add the poster in as a separate object and move it into the same position as the solid. The other way was to take that solid we made and turn it into a pre-comp, which basically made it its own object that could be edited separately.  The last thing to do was to open the pre-comp (flat image), paste in the poster, and remove the background, thereby replacing the pink. 

We then made some tweaks to the solid to enable it to fit in the background better.  For example, blurring the object slightly, we reduced the brightness a little and changed the colour temperature eg cold goes towards blue and warm towards orange.  Lastly, we added some noise (grain).  

For the rest of the session, we were tasked to either make our own, or find some footage, to test the features we had learnt.

To test the motion tracking for myself, I chose a short video containing the back view of a boy as he was walking down an alley with high, concrete walls on either side. This enabled me to add some random text to the walls. I had many adjustments to make the perspective match the footage better, as the analysing markers didn’t quite get the perspective correct. One thing I noticed when running through my footage was that, when the camera was moving down the alley as the boy walked - the text on the walls moved along with the camera, which wasn’t ideal. However, with the adjustments, it was substantially improved.

Lastly, in order to make sure that elements added were properly integrated into the scene, we needed to ensure that our tracked element would not be visible if a person in the video were standing in front of it.

To do this we used the rotoscoping tool, which I was familiar with, due to using it in a past exercise. We used this in order to trace around the outline of the main figure and isolate them from the background. The last thing I had to do was take the layer and place it at the very top-most layer of the footage.