hi,
I have manually track some points. After I run the 3D camera solving, some of my tracking 3D cones are behind my camera. How to make sure all the cones are in front of the camera? My camera focal Length is set to constant initialized. how do i solve this problem? can anybody help me?
 
six

Hello,
 
Points behind camera usually mean they are badly reconstructed because they lack parallax. It may be caused by different situtations.
 
Is this a nodal shot (in this case the depth cannot be computed) ?
What are their 3D residuals ?
Is the whole solve bad (points having random depth), or only those points ?
Are they well track in 2D ?

hi Ronald,
 
Yes. My camera shot is a hand-held camera shake without any perspertive information. But my 2D track points are well track. I also have 3 helper frames, but doesn't seem to help .
( what is 3D risidual?) . After solving, my background become the foreground and vice versa. any tips to get a good helper frames shot?

Okay, so it's a nodal shot with 3 helper frames.
The best in this case for you is to use 2 of your helper frames as the reference frames (should be done automatically, but who knows).
To do so:
1- Launch the keyframes selection (3D Tracking\Initialize frames or Select Keyframes depending on your version)
2- Go to one of your helper and do 3D Tracking\Set Current Frame\First Reference, then go to a second helper and do the same with Second Reference.
 
That means the solve will start with your 2 helper frames, which usually contains parallax (perspective information). To be sure that the helper frames are good, you can solve them only (by moving the work area or setting all the other frames as "not solved" - see online doc for details).
Once they are good, you can solve the whole shot.