As a whole, your work here is extremely well done. It's very clear that you've focused heavily on your textures being made up of cast shadows for the most part, so you've been immersed quite thoroughly in thinking about these texture gradients as spatial reasoning problems, thinking about the forms that are present, how they relate to one another in 3D space, and how those relationships can be used to derive cast shadows which you can then employ in the creation of gradients moving from light to dark.

Because so many of these have been well done, I'm somewhat hard pressed to find things to provide useful feedback on, but I think I've found a particular area where your work still has room for continued growth. To be clear however, this is... beyond nitpicky, and it's really pushing the boundaries of my own capacity as well. I will relay to you the theory, but ultimately with the limitations we apply in this course and in this exercise - that is, working strictly in ink, not being able to erase, and therefore having to somehow hold the structures as they exist in 3D space in our minds and drawing only the shadows they'd cast, what I'm going to dig into in a moment is going to be... not just extremely difficult, but not something I'd really expect anyone to be able to achieve within any margin of reason.

So it's ultimately going to be more to further reinforce how we think about these textures and the shadows being cast, and is not something I'd consider to be a failing from any student.

It has to do with those textures made up largely of grooves and cracks, the kind of "negative space" where throughout the majority of the texture gradient those negative spaces get filled in entirely with cast shadows, as though we're really just filling them in without thinking about the 3D information that is present. While throughout most of the gradient it's not going to make an actual difference in the actual result, where it does have an impact is just before our gradient hits the extreme closest to the light source. In these areas, we're given just enough of a cast shadow for it to be visible beyond the forms casting them, but not enough to fill in the cracks fully.

If we look at number 20 on this page (the center row), we can see that you actually ended up creating the gradient by modifying the scale of the cracks themselves, making them larger on the far right and smaller on the far left, and even this much really limited how far you could push the darks, with the solid black bar on the left still being fairly distinct. To be honest I'm not entirely sure how I'd handle that end of a texture like this myself - probably by making more little cracks visible so as to build up more compound shadows (that is, shadows cast by multiple forms all merging together), but as noted above, it's the far right where the cracks themselves get very tiny in order to transition to solid white that I want to explore.

If we were to achieve this texture gradient while maintaining the exact same crack structures - that is, the same scale, no smaller cracks at all, the only option we'd have is to consider again how those structures actually cast shadows. That is, the walls of the cracks casting shadows into those cracks, without quite filling them in. This is where they admittedly get kind of weird.

Let's take a look at this diagram, where I've defined a slice of a cracked surface that might exist in this extreme end of the gradient. The diagram is divided into three sections - the top left shows the structures as they exist in space using construction/explicit markmaking, and the bottom left shows the shadows that those structures could cast on their surroundings, with the structural marks faded out but still visible. Finally, on the right side we have just the cast shadows on their own.

Notice how the cast shadows on their own don't actually look anything close to the cracks being entirely filled with black? Instead, the floor of the cracks (in the sense that the cracks have walls on the sides and a floor at the bottom) are split up into an area receiving shadow, and an area not receiving shadow, due to how close we are to the light source. It is this side-by-side of shadow and light existing together within each crack that is very easy to forget about, and to oversimplify by simply filling the cracks in entirely. Of course, as noted above, this is also a pattern of marks that is very difficult to derive in our textures without first having the structures drawn out, but it's still worth being aware of the fact that his is technically more correct than letting those cracks get smaller and then disappear.

Bringing it back around to the problem of creating a full gradient of cracks that truly goes from full light to full dark, then I suppose we'd have to start with a surface which is, structurally, very fill of cracks - so taking the surface in your example, we might zoom way out so as to increase that density, and then make the midpoint of the gradient similar to my diagram here, where the cracks themselves are half filled with shadow.

All that said, I think this would go well beyond the usefulness of this exercise. At the end of the day, the exercises we engage with throughout this course do have those limitations - for example, looking back at Lesson 5 and how we employ specific methodologies for constructing heads, though those approaches can be used when our animals' mouths are open, that doesn't make the exercise itself more useful towards its particular goal, and might actually cause it to be more distracting. Here, similarly, the cracks/grooves/etc. based textures might not be the most useful here, but they do give us a unique way to really force us to think about how we're really engaging with the forms that are involved.

To that end, it's probably best not to worry about those textures if you end up playing with this exercise again in the future if you want to focus on the exercise's goals, but it might be an amusing thing to try once... some day. Not that you'll catch me doing it!

Anyway - as I noted at the beginning, you've done a phenomenal job here with your texture analyses, and I think it's fair to say that from the students I can remember tackling this challenge (of which there are neither few, nor all that many), I'd say you're among those who've held to the core principles of this exercise the closest. I'll go ahead and mark this challenge as complete.

Before I go, there is one quick point I wanted to mention - I noticed that you've got two credits left unspent, and that might mean you intend to tackle the treasure chest challenge. This is a bit awkward to say, but if you do wish to do that, I'd like to ask that you allow some credits to expire (whether before or after the treasure chest challenge). It's easy to forget since it's mentioned all the way back in Lesson 0, but we offer the official critique track at a base price upon which we incur a loss, paying our TAs about twice as much as we require our students to pay to receive it so as to ensure we can provide the service as affordably as possible. In effect, we end up covering half the cost of offering that feedback. For the core/required lesson material to complete the course, that's a burden we choose to bear, but given the optional nature of the texture and treasure chest challenges, I figured I would mention it here. Sometimes students do have more flexibility in their budgets and are in a position to contribute back to our efforts and help us balance the scales for other students, and they simply forget that we very much don't derive a profit from the base cost.