/ic/ - Artwork/Critique

Okay so I have a little question. On the bottom right corner of the screen, I drew a cube like shape with 2 smaller shapes of more or less equal size on each side of the bigger one. All in one point perspective.

I then tried to draw it in 2 point perpective but my doubt is, how do I find out where to place the other smaller shape? How do I find out how big its supposed to be? Do I just eye it or are there other methods?

Okay so I have a little question. On the bottom right corner of the screen, I drew a cube like shape with 2 smaller shapes of more or less equal size on each side of the bigger one. All in one point perspective.

I then tried to draw it in 2 point perpective but my doubt is, how do I find out where to place the other smaller shape? How do I find out how big its supposed to be? Do I just eye it or are there other methods?