Planar Surface out of screen

Hello there,
I recently started on Mocha and I’m doing some training and tutorials. I would like to know why my planar surface goes of the screen (Disappear). I tried “Aligned selected surface” but when I do that the planar surface appears in the position when it disappeared before.

Thanks for your help

This is almost certainly your surface going behind the camera. If you using perspective when you track, it may be that your surface is going behind the camera in mocha and corrupting the data. In mocha, problem splines can occur when the tracking data has become so skewed it goes off or “behind” camera, the keyframes the tracking data generates can throw the shape information out of order. You may need to re-track the shape using only translation, scale, rotation, and shear instead of perspective. This is especially true for complex roto of an object that is turning away from screen or tracking an object that is turning.

Thank you for your respond Mary !