You probably will have to scale/ rotatte/ move the scene. Since it can't be calibrated, the AE 3D Tracker solution is arbitrary and from producing super tiny values to ones big as a galaxy anthinsg is possible. Using a plug-in like E3D that has its own problems with clipping and scale clearly doesn't make things easier. Start by checking your actual values. It could simply be that your "floor" is somewhere up in the sky or the camera uses a large zoom factor. Then find a script that scales the values.
First, did you set an origin and ground plane? It's important to do that. Second, since placing a text and solids work great and we have no idea what kind of footage or what effect you are using to create the 3D model I think that's where your problem is. It's always easier to get help when you give us a full screenshot with the modified properties (press the u key twice) of the layer giving you problems revealed. Cropped screenshots are seldom very helpful in diagnosing the problem. Just print screen and paste (Shift + Ctrl/Cmnd + 3 and drag from the desktop on a Mac).
I think the problem is how you are adding the 3D model of BB-8. Here's how I would approach the problem.
- After getting a good camera track set an origin and ground plane
- Add a solid and name it Start where you want your BB-8 model to start and verify that it is positioned properly
- If everything is good add a Solid to the place you want BB-8 to stop and name it End and verify that it sticks to the ground
- Set a position keyframe for the Start layer (solid)
- Move the CTI (current time indicator) to the spot in the timeline where you want the move to end
- Set a keyframe for the End layer and copy it
- Select the Start layer and paste
- Check the movement of the Start layer (solid) and make sure it is perfect
- Choose File>Export>Mason Cinema 4D Exporter and save the file
- Add the C4D project to the Project panel by choosing File>Import
- Add the C4D project to the timeline (or create a new comp using your footage)
- Select the C4D footage layer in the timeline and choose Edit>Edit Original
- When C4D opens up you should see your moving solid and have a camera
- Import your BB-8 model into C4D lite and copy and paste the position data from the moving solid to BB-8
(this may take some adjustment and grouping)
- When the model is working well and moving with the solid just turn off the solid in the object manager, add lights as needed and then save and return to AE.
That should do it. If you are using Element 3D for your model you'll have to go through a slightly different workflow but the idea is the same. Get your solid to move correctly from point to point in the scene, Any other workflow an animated 3D model and AE's Camera Tracker is going to be problematic and probably won't work at all.
If you are using 2D footage of BB-8 then Camera Tracker is the wrong tool. You'll want to stabilize the footage so there is no camera movement using AE's tracker and choose Stabilize Motion. All camera movement is now stopped. If the camera moves into the scene or has rotation you'll need to also track scale and rotation. When you have the camera motion removed you add the 2D footage and animate the scale and position as needed. Then you can add the motion back into the shot by adding a null to the timeline, renaming the footage "stabilized" and then adding this animation preset to the Null. Dropbox - destabilize Rotation Scale.ffx
This will add the following expressions to the null:
x = value;
y = value;
tx = thisComp.layer("stabilized").transform.scale;
ty = thisComp.layer("stabilized").transform.scale;
nx = x/tx*x;
ny = y/ty*y;
Now move the CTI to the first frame and make Null 1 the parent of the original footage and the footage of BB-8. This will put the motion back in the stabilized footage and add the camera motion to the footage of BB8
I hope this helps. It would have been easier to post a potential solution to your problem if you had given us a more detailed explanation of your workflow.