Cast shadows are the result of one form blocking light from reaching another surface. As a result, the actual shape of the cast shadow helps to define the relationship between the form casting it, and the surface receiving it, and has to be designed with specific consideration to how we understand that form. You may want to go back over these notes from the lesson which helps to address certain misconceptions students have (where they end up focusing entirely on what they see in the reference, trying to transfer it directly, rather than relying on first understanding the nature of the forms present in their reference, and drawing shadows based on that understanding).

Also, in regards to the crumpled paper part, this is a special case as explained in the homework section where it's assigned, as I've quoted below:

For the crumpled paper, you're actually not going to worry about cast shadows - instead, its purpose is to get you used to working with bold, clearly defined black shapes, rather than being timid and using hatching. Your crumpled paper study/gradient should be made up of clearly defined, distinct black shapes and white shapes. We find that despite breaking away from cast shadows, this helps students become bolder and more confident, which then yields better results for the other two textures that follow.

What we see in the crumpled paper is form shading instead (where the orientation of the surface, whether it's pointing towards or away from the light source, determines whether it should be lighter or darker). While we don't use form shading elsewhere in our drawings for the course, it is particularly helpful to use it in this one case.

As to the organic intersections, it is best that you take what Tofu provided and make an attempt to the best of your current ability, so we can better see what it is you do grasp and what it is that you don't, out of the feedback/information that you received.

Overall these are looking better, there's still room to improve of course but we aren't expecting perfection just that you try your best and take your time to follow the instructions to the best of your abilities.

Your arrows are looking much more consistent and have less stretching or flattening occurring which is a big step forward.

Your organic forms are looking simpler and it's nice to see that you're trying to shift the degree of your contours more.

You're still struggling with texture (which is normal) as you had explained, I'll include a big write up I've done on texture at the end of this comment that will hopefully clarify the process a bit more.

When it comes to your organic intersections you've made progress in some areas and some small new mistakes as well. Largely I can see that you're trying to think of how these forms interact in 3D space and the results pay off, these do look much better than your first attempt. Your forms do end up a bit stiff here, part of that may be caused by you not drawing through all of your forms which is something I'd like you to do going forward. Other than that your shadows are mostly hugging the form creating them rather than being cast on to the other forms believably, I can see that you're being more mindful of your shadows here you just need cast them further/with the contours of the forms below.

Overall this is an improvement and shows a lot more care in your work so I'll be marking your submission complete and move you on to the next lesson.

Keep practicing previous exercises as warm ups and best of luck in lesson 3.

Texture explanation

Rather than being able to give you just one or two pointers about things to work on, texture is often a case of people trying to simplify the steps too much and it's easier for me to just explain the entire process.

First things first, open up this leaf texture picture, I find leaves are a good example and a texture that people are often drawn to and do incorrectly.

The first thing you may notice is that this image isn't in colour and instead in black and white, this is helpful because people often get distracted by shifts in colour and will try to darken an area in their drawing if the colour happens to be darker. We shouldn't rely on converting images to black and white but it is helpful and something you may want to consider when practicing.

Now if I handed a student this image and told them to use it for their texture exercises there are two typical outcomes I would expect.

The first is that they would draw all of the veins (or many of them if they aren't extremely patient), and this would be an example of focusing on outlines.

The second result that I would expect is that instead of drawing the veins themselves they would either fill the veins in completely black or they would fill in everything but the veins completely with ink, and this would be them focusing on negative space.

This is where students get a bit confused at the start, they feel like they're looking at the image and drawing what they see but it comes out wrong. I should clarify that it's not necessarily incorrect, there is a time and place when obsessing over small details can be helpful but this is largely an exercise about learning how to imply information and thinking in 3D space. Remember that what we're learning here isn't observational drawing, it's constructional and while observation is definitely a part of the construction method there's an extra step that people tend to neglect in the beginning.

With that in mind let's go over the correct way to tackle these problems, bring up the leaf image (it's here if you closed it) and let's break down what we're working with. What people tend to neglect is that we're trying to think about the 3D space of the image we're observing and drawing. If we look at this leaf the veins are really just long organic forms, or cylinders if they're particularly rigid. The fleshy bit of the leaf could be thought of as either a plane or a thin box, and due to gravity's effect it will likely curve a bit (we don't need to think too much about it curving in this case because we're working so close up, but it's good to think of how the environment can have an effect).

To put it simply, a leaf is just organic forms that are intersecting with each other and a plane/box, just like the forms we practiced with in the form intersections exercise. With all of these forms in mind we can place a light source and depending on it's position and intensity we can create cast shadows much like we did in the organic intersections exercise.

An example of this can actually be seen in the picture itself. Let's just focus on the large main vein as well as the branching vein on the left. You'll notice that if you look along the bottom edge of the main vein there's a cast shadow, and on the right of the branching vein there's a shadow. From this information we can assume that the light affecting the leaf the most is somewhere to the upper left of the image and it's creating the cast shadows we want to draw.

This is an example of what drawing cast shadows might look like, it comes up early on in lesson 3 when Uncomfortable shows the process of drawing a leaf. You can see that he's not actually drawing the veins themselves, and instead just implying that they exist by creating cast shadows. Keep in mind that this leaf is fairly evenly lit and the point of the texture exercise is to work with light gradients but regardless it's a good example of what we're trying to achieve. There are times where capturing shadows doesn't immediately give the impression of what you're attempting to draw but it's just a single tool that you can use. You may not think that drawn leaf looks like a leaf, but if it was green, had a stem, and was attached to something that resembled a plant your brain would begin to fill in the gaps until it goes "oh that's a leaf".

Implying information helps both the creator as well as the viewer, it saves the creator time from having to obsessively capture every tiny detail and it prevents the image from becoming too visually noisy and overwhelming for the viewer.

Craig Mullins is a painter whose work I appreciate a lot and I feel does an amazing job of implying information through shadow, colour and brush strokes. I highly recommend looking up some of his work if you'd like some examples of just how powerful implied information can be.

Hopefully that helps you understand the process a bit more, best of luck again.