Hello SimonP, I'll be the teaching assistant handling your lesson 4 critique.

Starting with your organic forms there’s not much to criticise. Your linework appears smooth and confident, and you’re sticking closely to the properties of simple sausages for most of your forms.

It is good that you’re experimenting with shifting the degree of your contour lines, although usually the contour lines should be shifting wider as we slide along the sausage form, moving farther away from the viewer. This is also influenced by the way in which the sausages themselves turn in space, but farther = wider is a good rule of thumb to follow. If you're unsure as to why that is, review this section of the ellipses page where the degree shift is introduced. You can also see a good example of how to vary your contour curves in this diagram showing the different ways in which our contour lines can change the way in which the sausage is perceived.

Moving on to your insect constructions honestly you've done a pretty good job overall. There are a couple of things I’ll discuss which can make your constructions even better as you move forward with the next lesson, but overall you're showing a strong awareness of how every element of your construction is made up with simple, solid, 3D forms. As a result, most of your drawings feel very solid and believable as 3D objects rather than just a series of lines and shapes on the page.

The first point I need to talk about relates to differentiating between the actions we can take when interacting with a construction, which fall into two groups:

• Actions in 2D space, where we're just putting lines down on a page, without necessarily considering the specific nature of the relationships between the forms they're meant to represent and the forms that already exist in the scene.

• Actions in 3D space, where we're actually thinking about how each form we draw exists in 3D space, and how it relates to the existing 3D structures already present. We draw them in a manner that actually respects the 3D nature of what's already there, and even reinforces it.

Because we're drawing on a flat piece of paper, we have a lot of freedom to make whatever marks we choose, but many of those marks would contradict the illusion you're trying to create and remind the viewer that they're just looking at a series of lines on a flat piece of paper. In order to avoid this and stick only to the marks that reinforce the illusion we're creating, we can force ourselves to adhere to certain rules as we build up our constructions. Rules that respect the solidity of our construction.

For example - once you've put a form down on the page, do not attempt to alter its silhouette. Its silhouette is just a shape on the page which represents the form we're drawing, but its connection to that form is entirely based on its current shape. If you change that shape, you won't alter the form it represents - you'll just break the connection, leaving yourself with a flat shape. We can see this most easily in this example of what happens when we cut back into the silhouette of a form.

Fortunately you don’t cut back inside your forms very often, and the only significant example I saw is what I’ve marked with red on your crab. Sometimes this can happen accidentally, if there’s a gap between lines passing around an ellipse, and we choose one of the inner lines to represent the silhouette of the ball form we’re constructing, which does leave stray lines floating around the construction. Generally it is best to treat the outermost perimeter of the ellipse as the edge of the silhouette, so everything else remains contained within it. This diagram shows which lines to use on a loose ellipse.

On the same crab I also marked in blue some examples where you'd extended off existing forms using partial, flat shapes, not quite providing enough information for us to understand how they actually connect to the existing structure in 3D space. While this approach worked fine for adding edge detail to leaves in the previous lesson, this is because leaves are paper-thin structures, so essentially they are already flat and altering their silhouette won’t flatten them further. When we want to build on forms that aren’t already flat we need to use another strategy.

Instead, when we want to build on our construction or alter something we add new 3D forms to the existing structure. Forms with their own complete silhouettes - and by establishing how those forms either connect or relate to what's already present in our 3D scene. We can do this either by defining the intersection between them with contour lines (like in lesson 2's form intersections exercise), or by wrapping the silhouette of the new form around the existing structure as shown here.

This is all part of understanding that everything we draw is 3D, and therefore needs to be treated as such in order for both you and the viewer to believe in that lie.

You can see this in practice in this beetle horn demo, as well as in this ant head demo. You can also see some good examples of this in the lobster and shrimp demos on the informal demos page. As Uncomfortable has been pushing this concept more recently, it hasn't been fully integrated into the lesson material yet (it will be when the overhaul reaches Lesson 4). Until then, those submitting for official critiques basically get a preview of what is to come.

The next thing I wanted to talk about is leg construction. It looks like you were working with the sausage method for most of your leg constructions, and you’re doing a pretty good job of constructing chains of sausage forms.

It is good that you’ve taken a swing at building onto your sausage armatures on a few of your pages, adding the sorts of lumps, bumps and complexity that you observe in these structures, arriving at a more characteristic representation of the leg in question than what can be achieved with the sausages alone. I have some diagrams to share with you that I hope will help you to build onto your leg structures “in 3D” as you move forwards.

• These diagrams show how we can add to the construction with complete 3D forms instead of flat shapes and one-off lines.

• This diagram shows how instead of fully engulfing an existing form within a new one, we can establish a clearer relationship between the existing form and the new addition by breaking it into two pieces.

• This ant leg demo shows how we can take the sausage method and push it further, adding all kinds of lumps bumps and spikes to the sausage armature.

• I’d also like to share this dog leg demo with you, which shows how the sausage method can be applied to animal legs. This is significant, as we’d like you to stick with the sausage method of leg construction when tackling your animals in the next lesson.

So, you’ve done a good job with this lesson, and I’ll go ahead and mark it as complete. Keep up the good work.