I have a footage layer that has 3D camera tracker applied. I tracked the footage, solved the camera, selected my target and created a new camera with a null. I'm doing screen replacements on a group of stacked TVs using the "Shift+parent" method (shift+parenting the screen replacement comp to the null that's placed in the 3D camera environment. That way the screen replacement comp is automatically placed in the same z-space coordinates as the null.
I successfully tracked my first screen replacement comp onto the center TV, but now I want to go back to the original 3D Camera tracker layer and create more nulls in 3D space as I go. When I try to select "Create Null" I only get the option to "Create Null and Camera." I already have a solved 3D Camera layer in my comp, so I don't want to create another camera and therefore negate the other camera and screw up my screen replacement position. I want to keep adding nulls, with the same camera that's already present in my comp.
When I right click on my selected track point, these are the options I want to see:
...These are the options I am actually seeing:
As you can see in the top image, the screen replacement comp isn't tracked properly– it's scaled down due to the fact that I clicked "Create Null and Camera", which created another 3D camera layer on top of the camera layer that was already present. Only after I created a new camera and null did the option "Create Null" show up for me.
The only thing I can think of that might be causing this, is that I deleted a few position keyframes on my original solved 3D camera layer. I did this because a few keyframes were tracked incorrectly and were causing a jitter in the camera's position. (See image below- there is a missing position keyframe)
Is that my problem? Does editing the camera's position keyframes prevent me from seeing the "Create Null" option? Is there some broken link between "Create Null" and the camera's position keyframes?
Overall I'm just trying to prevent having to re-track my scene (RED footage=long track times)
After Effects 13.5.1
It works best to have a target selected (3points) before you add another null. You should be able to add a null with a single track point selected. It's working fine for me on OS X 10.11.1
I am not exactly sure what your camera is doing but I probably would have done this kind of a composite with screen replacements in mocha. Using the Camera Tracker works pretty well but to make perspective changes work perfectly, especially at the edges, requires removing all lens distortion before you do your tracking. AE cameras have no distortion so you are going to end up with ill fitting screen replacements at the edges that mochas corner pin tacking would handle with a lot less time and a lot less work.