Hi
i've been trying to edit one of my first video's in after affects. I came to a point that my 3d camera tracker wasn't working, after some research i've noticed that a part in the clip makes it fail, i've finnaly found that part and my 3d camera tracker works now. But not on a green screen, there he can't mark anything. How can i fix this? I need a clip projected and the green screen, but the video itself is moving. So i need it to stick to the wall 
se image below.
on this link you can see what i want to do, but the movie is moving all the time.
17
Replies
I took a look at the project. My first thought is that you created this shot of the house in a 3D app and added the grid there so why didn't you export the camera from the 3D app. Blender, C4D and Maya will all export cameras to AE. You would have a better match. I also wondered why the comp was longer than the shot.
Then I checked your camera track. The first thing I noticed was that Advanced Analysis was not turned on. The first thing you do when you have problems with a track is to turn this on and track again. The second thing I noticed right away was that the tracker points are very large and there are a bunch of them.
I then checked the layer on the solar panel and saw that the Anchor Point had been adjusted and the layer was nowhere near the surface of the solar panel. I also checked the other layers. Again, the position was off. This told me that you are using the wrong technique to attach the layers to the surfaces you track. Even if you picked perfect targets, you moved things and did not line things up incorrectly. You should only manipulate x, y, and z rotation, never orientation, and you should only move a layer into position using the x, y and z coordinates in the Comp Panel by hovering over them with the move tool selected until the axis you want to adjust is shows, then click and drag along that axis. Any other way of moving the layer into position will just foul up the position and you'll have to start over by adding a reference solid.
I tried using your original track and checked the right side of the house just selecting 3 points that gave me a target that looked like it fit, then I added a solid, set the blend mode to Multiply so I could see the grid inside, carefully adjusted the rotation, not the orientation, so that the solid looked like it aligned to the grid on the side of the house, then opened the solid layer properties and adjusted the height and width so that I could accurately position the solid on the grid. When I checked the track the solid very quickly slid off the surface of the house. This told me I needed to run Camera Track again.
I reset all of the transform properties on the layers you were using, deleted the camera and reference solids, and ran a detailed analysis again. After the camera was solved I deleted a bunch of track points and started with the right side of the house, added a solid and camera, changed the blend mode, adjusted z rotation, and position, then opened up the Solid settings and adjusted the size so it lined up with the grid. I checked the track and it was much better. I then added a solid to the front of the house only using about 6 of the track points, then moved down the timeline and added a reference solid to the solar panel, again only using about five or six points. Adjustments were made, in and out points were set for the layers as needed, and I checked verified that the reference solids were sticking to the surfaces they were supposed to be attached to.
It turns out there was a pretty consistent drift on all of the reference solids. This tells me the track is not accurate. It's probably because the camera used to render in the 3D app was not an optical camera but a perspective camera so AE couldn't get a good camera solve. It is close, but not perfect. The wide grid may also have thrown off the camera track.
It turns out the errors are pretty linear so just a few keyframes for the position, x, y, and z rotation, and sale let me get the solids stuck pretty well to their surfaces. Once that was done I parented the appropriate layers to the reference solids snapping them into position by holding down the shift key. I ended up with a comp that looks like this:
The solar panel took the most keyframes, but I got an acceptable composite on all surfaces. I thought about sending you the comp but decided that the best way for you to learn would be to carefully read this post, then try the same techniques yourself. The biggest problem I saw in your workflow was trying to adjust the position of the reference layers incorrectly and not doing a detailed analysis of the shot.
If you want to try starting over add a much finer grid with a lot thinner lines or something like a siding or brick texture to the house in the 3D app, add a texture to the ground plane and double check the camera and make sure that it is a normal camera, then render and track again. Trackable detail on more surfaces will give you a much better chance of getting a good camera solve.
You also might want to see if your 3D app can export a camera track to AE.
If your 3D file can be saved as a C4D file you could also import the file into AE and either extract the camera or use AE's comp camera to do the camera move there and add your elements. There are a lot more efficient ways to add elements to a shot like this than trying to run a camera track.
Here are a few 2D options for making composites look like they are 3D:
- Corner Pin Track in AE good for some shots
- Corner Pin Track using Mocha AE - better for more shots, more versatile
- Advanced Corner Pin Tracking using Mocha AE and adding CC Power pin as in this tutorial - even more powerful and it can be extremely effective for almost any shot where you have a planar surface you can track
- Mocha Pro Corner Pin Tracking
3D Options:
- Camera Tracking - great for some shots, won't work for others
- Camera Tracking combined with Mocha AE corner pin tracking to overlay a fine grid on the surface you need to track (that really needs about 200 words to explain)
- Syntheyes, the best considering price point, capabilities, performance, and integration with AE
- Camera Tracking + Reference solids exported to C4D, then C4D Lite + Cineware to composite 3D elements into a moving camera scene (again, about 200 words to explain how to do that)
- Camera Tracking + C4D the full version for more capabilities
- Camera Tracking + Element 3D - A very powerful alternative to C4D
Hybrid options:
- Export Camera data from 3D apps like C4D, Maya, Blender and use that in AE
- Import AE camera data and use that in 3D apps like C4D, Maya, Blender
The most efficient solution depends on the shot and the kind of composite you want to make. For example, I used Advanced Corner Pin tracking in this effects shot requiring replacement of the screen on a TV. I chose this technique because it was quick and gave me a very easy way to combine the reflections on the screen and the weather into the final composite.
The technique was also used on this shot which was part of a live demo I did.
The workflow allowed me to Time Remap a copy of the stabilized side of the truck and shift it's position so that it matched the shadow passing over the logo. You can't see it clearly in this screenshot but that simple blue logo covers up a UPS logo and the composite also has a reflection in the first part of the shot:
I hope some of this helps.
On the camera question, a perspective camera in some 3D apps is one that has an artificial vanishing point instead of a real one. This means that the perspective and parallax changes are not the same as you would get if you were actually standing in the scene. Some folks like to work with this kind of camera. A normal camera would have a normal vanishing point so the perspective and parallax are the same as you would get if you were actually standing in the scene. Perspective is controlled by the camera position, framing is controlled by the focal length. An Orthographic camera or view has no perspective or parallax. Rotate a cube and the nearest edge is the same length as the far edge. Put a normal camera close to a cube and rotate it and the nearest edge is much longer than the farthest edge because of the perspective and parallax. AE's camera tracker can only work with Normal cameras and it really helps if there are multiple planes, like the ground and the walls of the building, so the calculations will be accurate. Just calculating the perspective change on one surface is not going to give you a very accurate result and may be interpreted as a camera pan instead of a camera move.
Good luck with your project.
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