Post a link. You can put it on Vimeo or YouTube as unlisted or private if you like. Your description makes me nervous. If I were going to put 15 people in a green screen studio and move the camera around there would be some set pieces or other physical objects in the scene that I could easily track even if the shot would then require some roto. Having 15 people in the shot also make me worry that this is a shot that runs for several seconds, maybe even several minutes. Pulling of a motion tracked composite that is more than just a few seconds long requires some very careful planning and some very careful camera work. I did a 30 second walking open once that a was all green screen in a 130' deep studio. It took a full day of shooting background plates and a good half day of testing to get ready for the shot, and it was just one guy walking through a 'virtual' factory floor. I don't think we could have pulled it off without a Elemack dolly and 60' of dolly track at both locations(not my shoot by the way). If I had 15 actors to deal with I'd probably cut the action up into short sections that I could edit together later.
All that said, I'd be happy to take a look at the shot but you should have been asking for suggestions before you set up the shot and you should have included some sketches or story boards for your shot.
Thanks for your response.
I don't think it is nearly that complicated, as the camera filming the green screen shots is static. I filmed each greenscreen subject separately (as it is me I'm filming for a 15 voice track I recorded), and am trying to put them into a moving shot in a cathedral. The cathedral is in a 3d software, so I added blocks in where the actors will be, but I still can't seem to get a good track in mocha ae or AE's built in tracker.
I'd be happy if you would take a look at it, if you don't mind. I'll try to get you something today.
Wait, so you're trying to track a shot created in a 3d app?
There may be a way to get your camera animation from the 3d app into After Effects so that you don't need to track anything. At the very least, you can render the scene with lighting and textures specifically for tracking I addition to the version with the final lighting and textures.
I am working on a file in blender. Is it possible to export the tracking to AE?
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Ok, let me get this straight.
- You have set up a 3D shot with a moving camera - correct?
- Now you have a locked off camera and the actors (you) are not moving - correct?
If that is the case you have two problems to solve. The first problem is solved by extracting the camera movement from the 3D software and creating a 3D camera in After Effects. If you tell us which software you used to create your virtual set we can point you in the right direction there. When you have extracted the camera then you just key out your actor, make the layer a 3D layer and position it appropriately in the scene and orient the layer to the AE camera. That's all there is to that part. The only tricky part is positioning the 3D layer with the actor accurately and scaling it to the right size. If the actor was 10 feet from the camera on the green screen set but the actor is 40 feet from the camera in the 3D scene you'll have to move the actor 30 feet from AE's camera to accurately position the actor in the scene. With the right kind of information from your virtual 3D scene you should be able to figure out the position of the 3D "actor" layers mathematically. I must repeat, there is no tracking involved and there's nothing to track and the first problem is solved.
If you cannot extract the camera from your rendered scene then there is an outside chance that you can Camera Track the virtual set and come up with a viable camera extraction. When you get the camera extracted then you can add a solid or a null to the places in the scene where you want your actors to appear and then position your layers at the null's position and adjust the angle and scale to make them fit. This is a less desirable way to extract the camera and it's the only other solution that doesn't involve a bunch of manual work.
Because the camera on the green screen set does not match the camera in the virtual set you are going to have perspective issues to deal with and that is your second problem. You solve that by using CC Power Pin or AE's corner pin and trying to get the perspective on the actor to match the scene as well as you can. These adjustments will NOT be animated. You fix the perspective and forget it. The adjustments will also probably be very small.
If the actor is moving in the scene then you have another problem, and this one is very difficult to solve. This problem comes from the perspective mismatch between the cameras. There is NO tracking solution that I know of that will automatically fix this problem. If you actor is moving then the perspective is going to be off when they move and they will appear to float over the floor. You have to solve this by manually setting position and scale keyframes. You do this by eye, set as few keyframes as you can, and then just live with the result.
If you show us the footage of the virtual set we can probably figure out if Camera Tracking will work. If we know the 3D software you used to create the virtual set we can point you in the right direction for extracting the camera. Even Blender (http://www.blender.org) has a very good solution for extracting the camera and other data for AE.
I hope this helps.
Edit: Saw that you said you were using blender while I was replying to your post. Blender has a few export to AE options. Check out their site.
You should be able to find several resources. Just make sure you check out the source. There's even more bad tutorials and inefficient workflows for Blender in google searches than there are for AE.
Some resources here.
And, don't forget that After Effects also includes Cinema 4D Lite, so if none of those resources helps you go from Blender to AE, we can try to figure out a way to get the data from Blender into C4D Lite which can then be easily extracted in AE.
I actually just went into blender and changed the camera direction
Do I have to use the blender camera as my view, or can I parent the greenscreen footage to the blender camera and use my active camera, the footage just following the blender camera?
It is not easy. You have to go through the tutorials and make sure you have everything set up correctly or it will not work. Without seeing your actual project I have no idea what's going on.
I sent you the project file. Did you get it?
I actually ended up just getting my 3d app camera for the BG going at a constant speed and then just keyframing the subjects in place in AE- which ended up looking fairly good, once I figured out the proportions and so-on