Before I get started, I wanted to say that your wheels are really beautifully rendered - but, as we'll discuss shortly, it seems that you may have allowed your desire to render some really cool wheels and tires to distract you from the concepts we address in this course, and some of the limitations we impose in our approach so as to keep the focus on those concepts. We'll get into it more in the second section of my critique, but first let's take a look at the structural aspect.

Overall the structure of your wheel is solid. I can see that you've built it up around several ellipses of different sizes, avoiding the simple, rigid, cylindrical structure where your reference demanded it by having the cross-sections get wider to help convey an impression that the wheel is inflated, and would land with a bounce rather than a heavy, immobile thunk.

I'm also pleased to see that you took not only the outward faces of the rims' spokes into consideration, but also their side planes. They don't always read super clearly as a result of the rendering/shading, but I can see the intent, and that's what matters most to me.

Continuing onto the textural aspect of the challenge, here's where you admittedly dropped the ball. In a lot of ways we fully expect that most students don't fully remember the concepts, given how far removed we are from Lesson 2, and how very, very few students actually feel inclined to review it or include it in their warmups. In that sense, it's meant to be a trap where students are rudely reminded that the material exists, and that they should probably review it.

In your case, it feels like that may have been part of it, but I can't help but feel that you just really got excited to approach it in this way, and to create some cool pictures. You're fortunate you did it here, because we don't generally assign revisions for students approaching the texture through techniques other than those we teach here, but you're definitely going to want to take more care with things like that going forward, especially considering how time consuming the next and final lesson is.

I can see that once we get past number 10, you did move away from the ballpoint pen/hatching, and relying instead on areas of solid black, you definitely did seem to pull yourself back towards what we have students engaging with in this course, but there are some notable issues, mainly pertaining to the difference between form shading and cast shadows.

Form shading, which is what you've primarily used here, basically defines a relationship between a form and a light source. Where the form's surfaces face towards the light source, they get lighter, and where they turn away from the light source, they get darker. This is also why hatching lends itself to this kind of thing, because it allows us to create gradients very easily. As Drawabox focuses on understanding the relationships in 3D space between different forms, this relationship only involving one form at a time isn't terribly useful to us, and so as explained here, it's not something we worry about here.

Cast shadows, on the other hand, are our bread and butter, because they involve a light source, a form casting the shadow, and then another form (or several) whose surfaces receives that shadow. This means that the actual shapes we use to design our cast shadows, through the design of that shape itself, allows us to convey a 3D spatial relationship (the one between the form casting the shadow and the surface receiving it). So, it is highly applicable to what we're studying in this course, and the shadow shapes themselves play the same kind of role that hatching lines would, except that they actually convey information specific to the surface in question, whereas hatching is often more generic, usually being used to convey the shading itself.

Along with being more tightly related to what we're studying here, there are other benefits to this kind of approach. Where explicit markmaking (which shading, outlining, and really any situation where you directly draw the form in question) locks you into a certain level of detail, or density of detail, for the entirety of that object, implicit markmaking is much more flexible. In other words, it allows us present just enough information for the viewer to understand what the texture of a surface is, without having to draw each and every textural form.

This is handy because we the wheels as you've drawn them here may look awesome in a void, or as the focus of your illustration, but if you were drawing a car and they were as heavily rendered and detailed, they would immediately draw the viewer's attention, becoming a strong focal point whether you want it to or not.

Implicit markmaking allows us to use the shadows those textural forms cast to suggest their presence. 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 despite working off the exact same form, how you draw the marks to convey it to the viewer may be different depending on other circumstances. It might have a looooong shadow, or it might be so close to the light source that it has no shadow at all. Just this potential for them to be different gives us a lot more freedom in terms of where we choose to concentrate our detail (which would be cases where the cast shadows are neither so big that they all blend together in a single, black, no-contrast mass, nor small enough to all be blasted away, reading as a single, white, no-contrast mass), and where that detail is more visually sparse.

Now, before I call this critique done, there's one last thing I wanted to share with you, although it's not specifically related to an issue present in your work, more just information I wanted to provide, as it's relevant. 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.

And with that, I'll go ahead and mark this challenge as complete. Do be sure to go back over the texture section from Lesson 2, starting with these reminders.