This assignment has two keys: #1 and 5. You are to do the three inbetweens.
You are to draw the three inbetweens for each box. #3 is a half and 2 and 4 are quarters.
This has the same theory behind it that the last assignment did, with the spheres. Now, this time it's boxes and perspective that you need to deal with.
I'll give you three options for these:
Using the color guides, rotate the two boxes so the red side and green side inbetween properly.
This assignment is going to force you to start thinking three dimensionally.
Find the corresponding corners and draw an arc to describe the path of action. Don't make it a straight line, put a curve into it. You choose the appropriate amount. Start with inbetween #3 and take your time. As you flip the two keys try to visualize the movement and see the shape in your head. It's quite the brain teaser at first.
Try using the shift and trace method after you have drawn the main path of action.
Once you have #3 done, continue on with 2 and 4, then flip all the drawings in order to see the rotation.
If you want to, go back and add in another inbetween, between each drawing.
Here's a pencil test of version 2, the left box. I've added in an additional 12 inbetweens to make the action smoother.
Here's the fixed version.
See my inbetweens