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How to Draw the Rib Cage – Step by Step

May 14, 20152 Comments

In the last episode we learned the anatomy of the rib cage. If you haven’t seen that one yet, make sure not to miss it.

In this episode, I’ll show you how to draw the forms of the rib cage step by step.

DRAWING 1

Rib Cage drawing reference

I always like to start my drawings with the biggest shapes first. In this case it will be the egg-like shape. It’s thinner at the top where the neck attaches, and thickest about ⅓ from the bottom. Try not to draw the entire shape with one stroke. Construct the shape with many segments, analyzing the angle of each line as you go. Constructing a shape from many angles like this allows you to visualize the shape and spend more time making sure it’s the correct shape. Rather than doing it in one stroke hoping your hand lands in the right spot. You can see how with this shape I established the angle of the top plane, front plane, the angle between the corners of the rib cage, and the curve of the bottom and back.

Starting lines for Rib Cage


I’m being specific about each section of the shape while maintaining the tilt and the width to height relationship of the overall shape.
Rib Cage tilt and height to width ratio

Top plane of rib cage
Bottom of the sternum
The top plane of the rib cage
tilts forward, so keep that in
mind as you try to visualize
the planes.
Find the bottom of the sternum.
Remember, it’s about half way
between the pit of the neck
and the bottom of the rib cage.

Rib Cage thoracic arch
The cartilage that defines the
thoracic arch starts from the
bottom of the sternum. So, from
there I’ll extend the thoracic
arch shape, while considering
the way perspective would
affect that shape.
I like to relate one side to the
other and make sure that the angle
of that line follows the angle of
the front plane as if this was a box.


Rib Cage bottom plane
Rib Cage sternum
This side of the bottom plane
is covered up, but I’ll ghost
it in anyway so I can visualize
these forms better.
Indicate the edges of the sternum,
curving over the front plane.

Rib cage xiphoid process
Rib cage front plane
A little notch in here for
the xiphoid process
And we need an indication for the
edge between the front plane and
side plane. This is like the edge
on the box.

Rib cage plane allignment
Everything on the front or back
plane will be at this angle, like
a box in perspective.

DRAWING 2

Let me show you what I mean when I talk about the rib cage being a box.

Rib cage box 1
Rib cage box 2
We’ll think of the front
of the rib cage as this
flat plane that’s rotated
slightly to the left and
downward.
The widest part of the rib cage
is ⅓ from the bottom, so from
there I’ll extend a plane inward.
Still part of the front plane
just getting narrower.

Rib cage box 3
Rib cage box 4
From that, we can complete
the box with a side plane
and top plane.
So, we have the big simplified
volume of the rib cage, and we
can just draw the shape of the
thoracic arch right on it. Start
by finding the bottom of the
sternum and then some major
angles downward toward the corners.

Rib cage box 5
Rib cage box 6
And since the thoracic arch
is an opening, we can see
the bottom edge on the far
side. It will be parallel
to the other bottom edge.
Let’s clean up this back side.
Ok, so that’s the front of the
rib cage.

DRAWING 3

Rib cage drawing reference 2

The major structure from the back is very similar, but the wedge shape at the spine is a bit tricky, so I want to show you how to do that.

rib cage back view 1
Start the major shape in the same
way I do for the front. Constructing
that shape in parts.

rib cage back view bottom plane

For this bottom edge of the back plane, I’m observing the angle here on his back and trying to imagine what it would look like of it was a box. And then it transitions to the angle of the side plane.

rib cage back 3
Find the edge between the side
plane and back plane. At this
point it should look like a
simple 3 dimensional form.
Notice that even though he is
leaning back and toward us a
bit, we’re not seeing the top
plane of the rib cage.
That’s because the top plane
tilts forward, so in most back
poses the top plane will be
hidden behind the back plane.

rib cage back 4
rib cage back 5
The 12th rib actually connects
to the spine up here and then
angles downward.
So, I like to define that edge.
It’s the same edge that we
ghosted in from the front view
in the previous drawing.

rib cage back 6
It’s a continuation of the
thoracic arch as it curves
around the bottom corner of
the ribcage and comes back
up to connect to the spine.
Ok, this is the part that I wanted to go over.
Remember in the previous video I mentioned
that the back plane has a concave wedge that
holds the spine. To cut this wedge shape out,
we can think of 3 planes. One center plane…

rib cage back 8
…and 2 side planes. The center plane
just follows the curvature of the thoracic
vertebrae. On each side of this center plane,
we’ll have a inward facing side plane.

I want to point out that this S curve is highly exaggerated by the trapezius muscles. The spine will curve a little bit, but the curve we’re seeing here is the muscle pushing in past the center line.

Thoracic spine rotation does affect the rib cage, but not nearly as much as this pose might suggest. Ok, let’s get back to that wedge.

rib cage back planes 1
rib cage back planes 2
This might just look like
4 vertical lines to you,
but try to imagine the cross
contour of this surface.
This plane angles like this.
And this plane angles like this.

rib cage back planes 3
rib cage back planes 4
This is part of the back plane.
And this is also part of the back plane.

rib cage through-line 1
rib cage through-line 2
If a trail of ants marched across
this surface, that ant trail would
be the cross contour line. Around
the side plane…
…across the back plane…

rib cage through-line 3
rib cage through-line 4
…down the wall of the wedge…
…across the center…

rib cage through-line 5
rib cage through-line 6
…then back up the other wall of the wedge…
…and across the rest of the back plane.

Keep practicing drawing the forms until you have them memorized. If you’re struggling with perspective, go back and rewatch my video on structure. Practice drawing boxes in perspective. Once you can easily draw a box, then you can start making that box more complicated by cutting out wedges.

Rib Cage Assignment Examples

To view all 10 rib cage assignment examples, sign up for the premium anatomy course!

For additional help, watch my critique session on the rib cage. I go over student submitted work and provide insights on how they can improve their assignment examples.

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Comments (2)

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  1. Saul says:

    Hi Stan,

    Unbelievably amazing stuff here.
    Still cant understand where core rotation is generated in your extreme rotation example. You are drawing rib cage as rigid box. Also in previous lessons you have mentioned that rotation is not occurring in waist area. So where ?

    Regards
    Saul

    • It’s not coming from the lumbar vertebrae. It’s coming from the thoracic vertebrae. Also, a lot from cervical vertebrae (rotating the head). And as I mentioned in the video, the position of the scapula creates the illusion that the top of the rib cage is rotated more than it actually is. It is rotated, just not as much as it seems.

      “You are drawing rib cage as rigid box.” – You’re right. I should have shown more twisting of the form of the rib cage. Thanks for pointing it out 🙂

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