Congrats on completing the cylinder challenge! I'll do my best to give you feedback so that you can improve.

Starting with your cylinders around an arbitrary axis, the first thing that stands out to me is that all the cylinders look the same which means you haven't varied the rate of foreshortening on them. For cylinders, 71 and 68, you appear to have your side edges running basically parallel to one another on the page. This challenge has us rotating cylinders freely and randomly in space (as we did for the box challenge), and unfortunately a vanishing point would only go to infinity (resulting in lines parallel on the page) if the set of edges they represent are running perfectly perpendicular to the angle at which the viewer is looking out into the world. In other words, we only draw them with parallel lines on the page if the edges themselves aren't slanting towards or away from the viewer through the depth of the scene, but rather running straight across their field of view. Given the random rotations we use in this challenge, this perfect of an alignment is not something that would happen often, if at all, and so forcing those vanishing points to infinity would be incorrect. You do fortunately have many cylinders that don't have parallel side edges like that although are very close to parallel. Everything else you are doing correctly so just by varying the rate of foreshortening can help you get more out of the exercise.

Continuing onto your cylinders in boxes, overall you've done pretty decently here, although there are some points to pay closer attention to. This exercise is really all about helping develop students' understanding of how to construct boxes which feature two opposite faces which are proportionally square, regardless of how the form is oriented in space. We do this not by memorizing every possible configuration, but rather by continuing to develop your subconscious understanding of space through repetition, and through analysis (by way of the line extensions).

Where the box challenge's line extensions helped to develop a stronger sense of how to achieve more consistent convergences in our lines, here we add three more lines for each ellipse: the minor axis, and the two contact point lines. In checking how far off these are from converging towards the box's own vanishing points, we can see how far off we were from having the ellipse represent a circle in 3D space, and in turn how far off we were from having the plane that encloses it from representing a square.

In being as fastidious as you have been in applying the line extensions as instructed, I can see that you've been giving yourself ample opportunity to assess where your approach could be adjusted to bring those convergences together from one page to the next. As a result, your awareness of those proportions have improved, and while there is of course still plenty of room for improvement, you should be well equipped to tackle the related issues that arise as we tackle Lesson 6.

That's pretty much it! I won't be assigning revisions but just make sure that you work on varying the rate of foreshortening on your cylinders. If you are unsure about anything or have any questions feel free to reply with them!

Good luck in lesson 6!