3d problem with a simple title game

Processing Libraries
8

the depth is at 0 or -50 constant

 Rigaecolonna.set(r, c);
    img = createImage(width/ righe, height/ colonne, RGB);
......etc
    cordinate.set    (Rigaecolonna.x*img.width, Rigaecolonna.y*img.height, 0);
    lati.set(cordinate.x+img.width, cordinate.y+img.height, -50);
etc 
    shape(cubo, cordinate.x, cordinate.y);

this is the printing of the coordinates of the upper right corner of the cube I am going to draw, the second row with the side l are the coordinates of the end of the side, all with 2 rows and two columns in a window 900 * 600, if a cube starts at 0 and ends at 450 and the other starts at 450 why do I get this? where does the space between the cubes come from?
I thank you for your patience, but I read the tutorial on 3d and I tried with the perspectives and with the screenX but I can’t get a wall of cubes like in 2d
0.0 0.0 0.0
450.0 300.0 -50.0l
450.0 0.0 0.0
900.0 300.0 -50.0l
0.0 300.0 0.0
450.0 600.0 -50.0l
450.0 300.0 0.0
900.0 600.0 -50.0l
the first probable cube was empty to make the game
Cattura