17 was a sketch but I liked it so much that I sent it in this isolated form, I hope there is no problem

Before I get started, I'll be keeping in mind that you ended up having to complete this challenge freehanded, rather than with the use of an ellipse guide. While I assume that you made a concerted effort to try and get your hands on one (as it really does help to ensure that our cognitive resources are focused on the aspects of the challenge itself, rather than the drawing of the ellipses), sometimes that's not the easiest thing to do.

Jumping right in with the structural aspect of the challenge, you've made good use of laying down successive ellipses to build out the structure with control, allowing you to consider how much of a curve the profile should have (resulting from the middle either being wider than the sides) based on the individual wheel/tire design. This helps to convey either the sense that the tire is more inflated and might land, if dropped, with more of a bounce, or if it'd be really solid like some industrial vehicle tires can be.

You've also handled the construction of the spokes of the rims quite well, with clear attention to not only the outward face of the structure, but also its side planes so as to give it a stronger sense of solidity. Given our restrictions in this course, where we're working with solid black and white, I would recommend avoiding filling in those side planes with solid black. It can be a little visually confusing at times (since it takes an extra moment for the viewer's brain to determine whether it's looking at a paper-thin front face and a shadow being cast, or whether it's meant to be the side planes that are just shaded in), and by sticking to reserving those filled areas of solid black for cast shadows only (as discussed here back in Lesson 2) it helps us to communicate more clearly with the viewer. This also goes for cases where we might simply fill in a void space, like the holes in the rims of number 22. Being more specific and discerning with how we use these visual elements can help reduce the friction involved when a viewer tries to make sense of what they're seeing.

Continuing onto the textural part of this challenge, by and large this part is intended as something of a trap. Being as far removed from Lesson 2 as we are, it's very common for students to forget everything we talk about when it comes to textures, and the use of cast shadows for implicit markmaking. While the majority of students do fall fully into this trap (either opting to construct their textural forms as they would anything else, by outlining them directly, or by using filled areas of solid black but for things other than cast shadows), I can see quite a few signs here that you were more aware of the concepts from Lesson 2 than most, at least earlier on. Cases like 12 make this very obvious, where you were clearly trying to figure out how to approach having your forms cast shadows on their surroundings, and other cases (albeit to a lesser degree) also showed a certain amount of uncertainty and continued struggle to figure out how exactly to go about conveying these textures.

In large part you did still end up falling back to approaches that aren't exactly what we're looking for, but I am admittedly still pretty pleased. Texture using the methodologies we employ here (which are always tied back to spatial reasoning, so there are many strategies one might use to convey texture in a drawing but what we teach here is less about how to draw textures, and more about how we can use the concept of texture to reinforce the same things the course is narrowly focused on teaching) is very difficult, most of all because it relies on drawing cast shadows for forms we haven't yet drawn.

The core of it comes down to what's explained in these reminders. We always want to make sure that we're first outlining the intended cast shadow shape, then filling it in, because the act of drawing the outline is one where we actually think about the relationships between the form casting the shadow, and the surface receiving it. While observation is important, it's not that we want to observe the cast shadows that are present in order to draw them directly. We observe to understand the forms that are present, and then we leverage our spatial reasoning to decide what kind of cast shadow that would produce given the specific context in which that texture is being applied.

The reason we use implicit markmaking instead of explicit is fairly simple, although it's not always obvious. A wheel drawn entirely through explicit markmaking/direct construction might look excellent floating in the void, all full of detail, but when it becomes part of an existing drawing, all of that packed detail can actually work against you by drawing the viewer's eye to it whether you want it to or not. This interferes with our ability to control composition (which is all about dictating how the viewer experiences a piece, what they look at and in which order), which while outside of the scope of this course, is still something I want to give students the tools to engage with more easily.

Explicit markmaking basically locks us into an agreement with the viewer: whatever is drawn is present, and whatever has not been drawn, is not present. And therefore to convey each textural form, we have to declare its presence explicitly. Implicit markmaking on the other hand gives us more freedom by disconnecting the marks we draw from the specifics of what is present.

To achieve this, we leverage the very nature of cast shadows. As shown in this diagram, depending on how far the form is from the light source, the angle of the light rays will hit the object at shallower angles the farther away they are, resulting in the shadow itself being projected farther. This means that even if we're setting aside concerns like keeping our light sources consistent (which does matter, but is outside of the scope of this course so we'll set it aside to avoid further overcomplicating things), just the fact that the same form might cast an entirely different shadow if it were in one location versus another, returns to us a certain amount of control over how that information is conveyed.

Another point to consider is that when it comes to those tires with shallow grooves, or really any texture consisting of holes, cracks, etc. it's very common for us to view these named things (the grooves, the cracks, etc.) as being the textural forms in question - but of course they're not forms at all. They're empty, negative space, and it's the structures that surround these empty spaces that are the actual forms for us to consider when designing the shadows they'll cast. This is demonstrated in this diagram. This doesn't always actually result in a different result at the end of the day, but as these are all exercises, how we think about them and how we come to that result is just as important - if not moreso.

Before I call this critique finished, there's one additional bit of explanation I wanted to provide. It's something I share with students where I feel it's appropriate (it's prewritten/drawn, not unique to this critique), but it may help you better understand the thinking that goes into the way in which we tackle texture. Take a look at this diagram. It refers to the Lesson 2 texture analysis exercise:

• First in the traceover of the reference image, we're identifying the kinds of forms that are present and how they vary/how they're similar.

• Then in the first rectangle labeled "the forms we're transferring" this is more of an idea of how we would, in our heads, think about arranging those textural forms on our surface based on what we saw in the reference.

• Next in the rectangle labeled "how we're thinking about the cast shadows" are the actual lines we'd be drawing to design those cast shadow shapes, based on our understanding of the relationship between each textural form and the surfaces around it. The forms from the previous step are faded out here, because again - they weren't drawn. This is definitely the most challenging part, because working implicitly requires us to think about multiple forms simultaneously without drawing them - though not all at once, more a small handful including the one whose shadow you wish to design, and those whose surfaces that shadow might touch.

• And finally, we'd fill in those shadow shapes.

• Once the shadow shapes are in, while we can't take away from them (since we're working in ink), we can add to them to extend our cast shadows as needed to adjust and push the gradient.

Anyway! All in all, you've handled the wheel challenge reasonably well, and I'm glad to see that you were clearly thinking about how to tackle those textural problems, rather than simply defaulting to something more comfortable, even if you didn't exactly know how to go about it. I'll go ahead and mark this challenge as complete.