First, you need to understand the visual representation of perspective: it means that lines that are parallel in real life will appear as gradually tapering toward each other. One perfect example is the room on your picture:
- the top and bottom of the walls would be parallel in real life, correct? Well in this image, it is tapering the further it goes.
- the floor would have parallel edges on the left and the right in real life. In the image, the edges are getting closer together as they are further from the viewer.
This means that you have to look at objects in the same way. If you look carefully, the box on the left already has a perspective on it: the square top is not really showing as a square because it is tapering. Same with the height of the box, from the front “corner” to the back ones. So that one would not need any tweaking.
For the box on the right, you can see that the tapering is much much less. It is still there, but just a tiny bit.
The challenge, in this case, is not the perspective per se, but the angle of view. For the left box, the angle of view is from more above than with the right box, while the box on the right is seen from “not soo high”. Basically, it means that those two boxes would be hard to fit in a single collage to be consistent together.
I think it would be difficult to adjust one box (mostly the left one) to match the right one and the room because of that angle of view.
I think this might require a whole class to explain 🙂