So clear outlines always foster a sense of "sticker optic" / "lack of depth"? I
nope, but you need to know a lot about form, to get an outline which conveys form.
thought it was mainly a matter of good shadowing to reach a high sense of depth/dimensionality but an ordinary (real) 3d-form (like a garlic) doesn't have an outline that distinguishes between the body of the form and its border. It's all just a set of bodies forming a whole object, no borders inbetween there.
the shilouette (outline) and the shading are equally important.
If you actually check the garlic with the photo, it's slightly off in a lot of spots. But it's close enough to look believable.
You just need to get close enough.
Reality is the best source for outlineless objects.
I can see how it would be more difficult to develop a sense of depth working with a lineart-approach. So a lack of clear border lines and good shadowing could be considered the core of creating dimensionality? Is there something else?
It's not more difficult to reach good forms with lines, it's about as hard as correct shading is. It's just the 2 smaller building blocks which lead to the solution of a bigger problem.
The thing is that you *have* to understand how form is working in reality.
And then you can abstract the form in lines or clusters - means to an end to actually describe form.
the basic technique to master of how to get a solid form drawing is perspective.
Although it's possible to use clusters in a graphical pattern-wise approach as well.
take for example cubism styled art
form approach: (the goal is to get depth with clusters)
pattern approach (the shapes look flat, but there is also no actual attempt to achieve any understandable 3d-form)