Well, that line can exist, but it's an effect of musculature and happenstance alignment. Probably folks draw it that way because in 'heroic' anatomy, likely stemming from early Greek tradition, there is a noticeable arch on the torso there as a result of stylized abdominals up top that SEEM to connect to the rising ribcage. This shape was/is exaggerated to produce a visually pleasing semicircle, since the top attachment of the abdominals can seem to line up into that idealized arch. Seen here and here.

It's important for aspiring artists to take an anatomy class to differentiate between muscle and bone, so as not to treat shapes they see so simply. It's indeed not bone, but it is an example (if understood) of how the body's parts can be made to line up to an idealized and frequently nonexistent-in-nature aesthetic.

While I do agree with you that some forms of musculature may influence the look of the bony landmarks and crevices, I think the overall plane shift between the sternum plane to the shift of the gap of abdominals clearly indicate the form of the ribcage, or implies it.

What I think most artists don't take into consideration is how far down the pectorals should go down the sternum.

Another issue too when people draw their anatomy with circular masses instead of beginning with the skeletal bone structures then attaching the origin and insertions of muscular form are the collar bones and gaps between the deltoids and pectorals.

I don't know if I make any sense. I'm still an amateur, but I hope my opinion is valid!

I am simply noting the art history tradition to be aware of, because it is a stylized and purposeful alteration of existing anatomy- one must understand the base of what they are stylizing if they wish to do so! Plus, on very bulky people, you won't always see the ribcage and people observing may mistake firm muscle for bone in that case. Unfortunately I cannot post links from my phone! But yes, the muscles can and do change the way those areas look and if an artist is aware of that, they can make an informed stylized decision like the Greeks did... but otherwise you get mushy mistakes!

It took me a while to re-read your comments/images and the compare it with Kris' illustration to get what we're all saying.

I figured out you're completely right, there is a semi-circle framed by the upper origins of the abs, paired with the external obliques and lateral serratus muscles that cover the rib cage structure! There was a miscommunication that I didn't entirely register until I took a good long look. I took for granted those muscles illustrate their own lines to create pleasing rhythm over the skeletal form.

My interpretation of Kris' point was people confuse that "arbitrary line" for the structure of the actual rib cage. Beginners don't study the skeleton and they base their knowledge out of the superficial details of the musculature.

What I got from you is that arbitrary line exists because of the way the ab and external oblique muscles line up, so the arbitrary line has a purpose there depending on the stylistic interpretation of the human structure/anatomy. That it's not wrong to draw the line at all, it has been done through history by sculptors and painters alike. Which is true! I totally agree with you.

My point was the overall form of the rib cage is still prevalent through the bony landmarks and indents of the muscle origins, with a few superficial muscles wrapping around the larger forms creating the "arbitrary line" you and Kris highlighted. That beginners take the lines as is without going a bit deeper and figuring out the base architecture of the skeleton is truly the foundation for form, gesture, and anatomical accuracy. I would look through the two Greek/Roman sculptures and still spot where the edges of the ribcage were and the frontal edge of the plane shift of the sternum was.


Hah, I learned a bit from you and Kris, thanks!

What people make is an arbitrary line, probably boiled down from a real thing.

What I do is think more in planes and geometry, personally, and then this line DOES NOT BELONG, it is a tiny surface bump and not the carved thing some do.

Yeah. Structure wise it doesn't make sense to make this line the plane shifting point!

I boil my drawings down into plane structures too, and usually start with the skeleton, then add muscle mass to it later.

The awesome thing about working with planes, as you do, is if you understand basic lighting, you can break it all down with much more relative ease logically!

You are absolutely right, and thanks for the examples. I fear people try to CONSTRUCT this way, so I want to, as best as possible, explain to them that such is fail. Explaining will be difficult D:

Oh totally. I hope some beginners do see this and maybe these posts and see: "Oh! I'm not crazy... that shape sort of exists, but I thought it was the ribs..." or something? Hmm. I know I had difficulty reconciling what I saw visible on the body with what those lines actually WERE. Anatomy classes, man, great stuff.

It becomes clear who has done figure drawing and really studied their anatomy shit when they ignore how crucial the skeleton is for structure.


Many beginners I've seen who don't understand how muscle works will arbitrarily add spherical form meshes to their drawing without giving muscles squash and stretch according to the way they contract and flex from their origin and insertions.

Bony landmarks really are the foundation for the human body. They're the hard stuff that don't move. If you can draw the skeleton accurately from any angle, you can draw the facial structures and muscles above it with relative ease.

I love it when I see artists do the plane shifts between the sternum and stretched abdominal muscles right by shading it accordingly!

Legs because: Broken knees... It bugs the shit out of me that folks don't understand knees don't bend backward, thusly creating concave shins. And Michael Turner knees >:( Also the 'gap' does not exist on 99% of women out there, just like every guy isn't a perfect "V".

More torso- Twisted ribcage- frequently people draw both shoulders from the back at a 3/4, or only one shoulder from a side, but somehow, magically we see both boobs/pecs from a front 3/4 angle.

Similar argument for faces as the above- skewed eyes and and muzzles.

Honestly I would be the worst person to advice people to not do those things D: I think I've decided to only give style tips and leave anatomy to someone else, because... compared to some of the commenters here I don't care enough, if that makes sense.