Jumping right in with your form intersections, overall you're handling these pretty well, although I did have a few notes to offer here. The only actual mistake I noticed was the intersection between the box and the cone towards the middle-left. I can kind of understand what you were thinking, but the orientation of the cone didn't really match that interpretation of their spatial relationship. Also, as I noted elsewhere on the page, it's best not to draw through your intersections (meaning, drawing the parts of them that aren't visible), except for cases where you're drawing a whole ellipse to get the curvature of an intersection right. While drawing through our forms (and you should definitely be doing it for your boxes) has big benefits for helping push our understanding of how these forms sit in 3D space, doing this for the intersections tends to make it a lot harder without very much benefit.

Continuing onto your cylinders in boxes, overall solid work, but the one towards the bottom right of the page is definitely a case where the proportions of the box you used was heavily stretched (as opposed to being proportionally square for the faces bounding either end of the cylinder). That in itself is not a problem, it's a normal part of the exercise - but what does make it a problem is when your use of the line extensions/error analysis fails to pick up on it. This can happen when we fall into comfortable patterns and going through the motion of identifying our line extensions, especially when it comes to the ellipses' minor axes. As shown here, your minor axes were not identified correctly, so you were never made aware of the issue.

Moving onto the form intersection vehicles, overall you did handle these correctly for the most part, but there are a few points to keep in mind:

• You don't have to drill down into non-primitive forms, although it's not a problem that you did. The exercise is about remembering that we're ultimately constructing volumes in space, and not just stitching together a forest of preplanned edges to reveal an object in the very last step. So as far as that's concerned, you handled it well.

• This one's also an issue with your form intersections, but I figured I'd only address it in one place - I'm not sure why you're going over your intersection lines with different colours, but it's best that you don't. Reason being, it creates the impression that the intersections function more like the line extensions from other exercises - as a sort of analysis separate from the construction. Our intersection lines are very much part of the construction, as they define where our surfaces change from following one trajectory to another, so having them all drawn in a consistent manner helps us to relate those intersection lines as being physical elements - like the weld lines between two metal structures that might be joined together. All in all, just avoid using multiple colours where exercises do not themselves call for it explicitly.

Finally, your vehicle constructions. Funnily enough, while I've called out little issues here and there with each section thus far, I am actually very pleased with your homework for the meat of the lesson. You have done an excellent job of both leveraging orthographic plans to think through your construction ahead of time, and in actually constructing them in three dimensions - all with a considerable degree of patience and care that really is one of the core elements this lesson tests in our students.

While there were some elements that still ended up being estimated (for example, how in both the front view and the side view these elements' bounds don't quite align to any existing defined landmarks, overall you were extremely thorough in identifying the necessary landmarks and making the decisions that were required to build up your objects confidently and with a clear sense of precision.

I am also pleased to see that when tackling the more organic protrusions towards the front and back of the same carriage, you defined them first in terms of chains of straight edges/flat surfaces, and rounded them out towards the end. I do think that sticking more closely to the straight edged scaffolding probably would have helped maintain more solidity on those structures in your orthographic plan (as shown here), I think you ultimately did end up moving closer to this in your 3D construction.

As a minor point, I would avoid filling areas with solid black as you did in this locomotive (at least given the other rules we adhere to in this course), and instead ensure that the only things you use solid black for are cast shadows - that specifically means cases where you're designing a shadow shape based on the relationship between a specific form or structure that is casting it, and another surface that is receiving it. The only case where we have a sort of exception to this, is where we fill the interior of our cab with solid black as you did here in this demo drawing, although we kind of tie it back to some semblance of consistency by saying that the exterior structure is casting shadows into the whole of the interior - but really it's because it helps with visual clarity. But aside from that, and more generally, when doing studies in the vein of what we do in this course, it's better to avoid arbitrarily filling existing areas with solid black, and think in terms of drawing specific cast shadows instead.

The only other point I wanted to call out is that you don't appear to be defining minor axes when constructing cylindrical structures, and that is definitely something you should be doing. It helps considerably with aligning the necessary ellipses correctly.

With that, I'll go ahead and mark this lesson - and the entire course - as complete. Congratulations!