Many thanks for your help, Keet.
Indeed, applies to my wall, the semi-transparency is effective.
I don't knw that it was essential to active just 1 step of transparancy in the 3D view, I just tried to apply this in opaque mode.
I de-activate 3D transpaency, because (I don't know why ...), when I Activate it, the floors bacame also transparent. On this view, I can see from 1st floor the car in the floor 0 :
https://pjjoint.malekal.com/files.php?i ... 0g14e12e11

You may have a solution for this also ?

Thank you again.