Luck Of The Draw

in the last episode we learned the anatomyof the rib cage. if you haven’t seen that one yet, make sure you don’t miss it. in this episode, i’ll show you how to drawthe forms of the rib cage step by step. i always like to start my drawings with thebiggest shapes first. in this case it will be the egg-like shape. it’s thinner at thetop where the neck attaches, and thickest about ⅓ from the bottom. try not to drawthe entire shape with one stroke. construct the shape with many segments, analyzing theangle of each line as you go. constructing a shape from many angles like this allowsyou 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 establishedthe angle of the top plane, front plane, the angle between the corners of the rib cage,and the curve of the bottom and back. i’m being specific about each section of the shapewhile maintaining the tilt and the width to height relationship of the overall shape. 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.

the cartilage that defines the thoracic archstarts from the bottom of the sternum. so, from there i’ll extend the thoracic archshape, while considering the way perspective would affect that shape. i like to relate one side to the other andmake sure that the angle of that line follows the angle of the front plane as if this wasa box. i’ll do a simplified version of the rib cage after this to show you what i mean. 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, curvingover the front plane.

a little notch in here for the xiphoid process and we need an indication for the edge betweenthe front plane and side plane. this is like the edge on the box. everything on the front or back plane willbe at this angle, like a box in perspective. let me show you what i mean when i talk aboutthe rib cage being a box. we’ll think of the front of the rib cageas this flat plane that’s rotated slightly to the left and downward. the widest part of the rib cage is ⅓ fromthe bottom, so from there i’ll extend a plane inward. still part of the front planejust getting narrower.

from that, we can complete the box with aside plane and top plane. so, we have the big simplified volume of therib cage, and we can just draw the shape of the thoracic arch right on it. start by findingthe bottom of the sternum and then some major angles downward toward the corners. 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.the major structure from the back is very similar, but the wedge shape at the spineis a bit tricky, so i want to show you how

to do that. start the major shape in the same way i dofor the front. constructing that shape in parts. for this bottom edge of the back plane, i’mobserving the angle here on his back and trying to imagine what it would look like of it wasa box. and then it transitions to the angle of the side plane. find the edge between the side plane and backplane. at this point it should look like a simple 3 dimensional form. notice that eventhough he is leaning back and toward us a bit, we’re not seeing the top plane of therib cage. that’s because the top plane tilts

forward, so in most back poses the top planewill be hidden behind the back plane. the 12th rib actually connects to the spineup here and then angles downward. so, i like to define that edge. it’s the same edgethat we ghosted in from the front view in the previous drawing. it’s a continuationof the thoracic arch as it curves around the bottom corner of the ribcage and comes backup 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 thatholds the spine. to cut this wedge shape out, we can think of 3 planes. one center plane,and 2 side planes. the center plane just follows the curvature of the thoracic vertebrae.

i want to point out that this s curve is highlyexaggerated by the trapezius muscles. the spine will curve a little bit, but the curvewe’re seeing here is the muscle pushing in past the center line. thoracic spine rotation does affect the ribcage, but not nearly as much as this pose might suggest. ok, let’s get back to thatwedge. on each side of this center plane, we’llhave a inward facing side plane. this might just look like 4 vertical linesto you, but try to imagine the cross contour of this surface. this plane angles like this.and this plane angles like this. this is part of the back plane. and this is also part ofthe back plane.

if a trail of ants marched across this surface,that ant trail would be the cross contour line. around the side plane, across the backplane, down the wall of the wedge, across the center, then back up the other wall ofthe wedge, and across the rest of the back plane. keep practicing drawing the forms until youhave them memorized. if you’re struggling with perspective, go back and rewatch my videoon structure. practice drawing boxes in perspective. once you can easily draw a box, then you canstart making that box more complicated by cutting out wedges. i hope you guys enjoyed this lesson! if youwant to see more drawing examples go to proko.com/anatomy.

i have 8 more examples, which serve as theanswers to the assignment from the last lesson. you’ll also find 3d models of the rib cageand the simplified rib cage, that you can rotate and draw from any angle. proko.com/anatomy if you’d like to win a free membership tothe premium anatomy course, go to facebook.com/prokotv and share the post for this video. i’llchoose a random winner next friday. good luck! if you like this video, share it with yourfriends, and if you want to be updated about new videos click here to subscribe to theproko newsletter. buh bye!

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