A lot of drawing exercises, especially those focusing on observational drawing, will involve taking what it is you see and transferring it to the page as accurately as possible. For what we're doing in this course however, that isn't the case - not exactly, at least, and not without additional steps and considerations.

The reference image serves as a source of information. It tells us how the forms are laid out, and in terms of texture it shows us what kinds of textural forms run along the surface of the larger structures, how they are arranged, and so forth. The reference photo conveys this information to us using light - we can understand the forms based on their shading, the shadows they cast, and so forth. But in terms of the source of that light, we're less concerned than we are about understanding the nature of those forms within the context of the reference.

What we ultimately draw ourselves, whether in the textural exercises or the later constructional drawings, is more of an application of that information, in whatever fashion suits our purposes. We aren't copying the reference image after all, we're reconstructing it using that information - it may not look identical, but the focus is on conveying the same overall information.

In understanding the nature of those forms, how they sit in 3d space and how they relate to one another within that 3d space, we choose how we wish to position our light sources, which in turn helps us in deciding how to design our shadow shapes to best convey the relationships between the forms casting them and the surface receiving them.

Furthermore because our focus here, in these specific exercises from this course, is on understanding and conveying spatial information, we aren't saddled with a strict need to keep our light sources completely consistent - just generally so. This gives us greater flexibility in placing our areas of parser detail vs. those areas of denser detail based on our needs, rather than being tied down only to how the reference image conveys it.

You can think about this in terms of language - let's say there is an an ancient scientific text written in Greek. In order to better understand it, you might attempt to translate it into English - the information being conveyed is the same, but in order to effectively convey it in a different language, we have to think quite hard about the underlying meaning, which in turn helps develop our understanding of it. In this case, the thing being translated is the spatial information itself.

You'll find a bit more in regards to processing our textural references in this section from lesson 2.