3d display disappear each Math.Pi

Question

Hi all,

I have a problem with my 3d display :

i have a grid made from wireframe of 3dtools library, the grid is on XY plane and the camera on Z axe looking at the plane.

when i turn the camera around the axe or whatelse, my grid disappear every 180° degrees !
If my camera is perpendicular at the plane, i see nothing, if it is a bit in perspective, i see some hashed lines.

Have you already got or heard some like that  ?

Thank
Winzo