making a 3d stroke 3d?

[Roland R. kahlenberg]

The technique involves splitting (CTRL+SHIFT+D) the 3D stroke layer and then moving the duplicate so that one is on top of the subject and the other layer is below. Repeat the stps as many times as is required.

HTH
Roland Kahlenberg
broadcastGEMs
customizable animated backdrops with Adobe After Effects project files

[Reloaded]

Well, 3D stroke is not actually a 3d object, so it can’t interact with any 3D layer from After effects, the only way to simulate it, is masking as people told you.

Pre-compose the 3D Stroke layer so it is consider as a flat video and then, duplicate it and mask one to the foreground and another for the background.

Good luck.