Now comes a point that many students have difficulty with - adding additional forms.
You'll notice that in most, if not all of my animal constructions, I try to use the same torso configuration. That is, as it covers the space from rib cage to pelvis, it dips down slightly, leaving a distinct curve along the spine.
In a lot of animals, you actually see bumps along this area, as you see in this wolf reference. In order to capture this, I will add additional forms to our construction.
The trick to doing this is to understand how these forms actually rest on top of each other. Too many students will just draw a shape on top, sticking it on as though it were a sticker on the page, and then after the fact go in with additional contour lines to cheat it into that third dimension.
This doesn't work - if the silhouette of the form you've drawn doesn't convey an understanding of how it sits in 3D space, and how it relates to the other forms in the scene, then all the contour lines the world will not salvage it. Instead, you need to think about how these forms are going to wrap around each other - consider the surfaces present, and how one form is being dropped on top of the other. This is entirely similar to the organic intersections exercise in lesson 2, and is the primary reason that exercise was covered there.