Monday, February 22, 2010

Perspective and the Figure - Part 2 : Joints

When I was a teenager acting out the customary role as Future Comic Artist (by which I mean copying and memorizing individual poses out of comic books), it was unsurprising that I became obsessed with the idea of anatomy.  I felt that "learning all the muscles" was going to magically make me a better artist, though it seemed like a daunting and impossible task.  I dutifully copied some diagrams from an anatomy book, and felt a little tinge of pride knowing what a deltoid was, or that the calf muscle was called the gastrocnemius (I skipped over the soleus).  However, I had skipped over two huge facets of anatomy: the skeleton, and perspective.

George Bridgman used a brilliant phrase as the title of one of his books on drawing the figure: "The Human Machine".  It's a good way to think about the figure.  From a sculptural point of view, a good exercise would be to build an actual machine out of metal and wood that mimics the functionality and range of motion of the human skeleton, using parts you find at the hardware store.  The goal would be to build something that could move in the same way as a human, but it wouldn't necessarily need to be shaped like one.  If we had some space-age synthetic muscle, we could rig it up to actually move.  What kind of joint would you need for the shoulder?  What would you make a vertebra out of, and how would it connect to its neighbor and how would it move?  How would you construct a pelvis so that there were joints in the proper places? 

The good news is that we don't actually need to build this machine- it's very helpful just to plan it out mentally.  The more accurately and true-to-life we can plan this machine, the better our understanding of the figure will be.  The bad news is that as two-dimensional artists we need to be able to draw it.  We don't necessarily need to be able to draw the actual parts we'd get from the hardware store- we can use some imaginary parts that have the same types of mechanical movement, and we can use simple masses for the bones. 

This inevitably gets back to perspective.  It's not enough to understand what a particular joint would be, we also need to be able to draw that joint and the major axes of the bones involved  from any angle.  Further, once we draw two joints, we also need them to be arranged in a way that would make sense given a single, fixed viewpoint and the ranges of motion for the joints involved.  One of the most common errors in figure drawing is drawing the different masses in a way that implies either that either the joints are in the wrong location or moved past their possible range of motion, or that the masses are in fact being viewed from different viewpoints.

Let's take one of the more simple joints in the skeleton- the elbow joint of the humerus and ulna.  In other words, the joint that allows you to bend your forearm up to do a bicep curl.  If we ignored the radius for now (which allows you rotate your palm), we could build this joint very simply for our machine: just a couple two-by-fours and a regular door hinge. When drawing, we can represent it with a long, thin box for the humerus, a long, thin box for the ulna, and an imaginary cylinder joint between them for the hinge.  Assuming the "elbow" isn't bent, things are pretty easy to draw, right?  From the sides and front, it's a piece of cake.  You could probably even tip it around in space fairly easily as well. 

However, once we bend that elbow a bit, things get complicated.  From the sides it's not too hard, and using that information we can estimate the front view fairly well (we're fudging the foreshortening).  But once we rotate our bent contraption, we get into trouble:

See?  Right away we are back at perspective.  How would you solve this particular problem?  If you have no idea, then how are you going to draw the arm in a similar position?  Even if you have the model posing in front of you, it's beneficial to understand that this particular perspective problem is at play.  If the pose is short enough, you will need this understanding to get something legible down quickly.  If the pose is longer (particularly if there are multiple breaks) you will need this understanding to compensate for shifts in the pose.

This is for one of the simplest joints in the body.  It's further complicated by the fact that the ulna does not actually line up with the axis of movement created by the cylinder joint- it's slightly skewed off in what's called the "carrying angle" of the lower arm (named because it allows space to carry objects such as a full bucket without it hitting your thigh).  To complicate things even more, the carrying angle varies from person to person, especially between men and women (due to the relatively wider pelvis and narrower shoulders of the female skeleton).  And we haven't even thrown in the radius.

A good first step to this kind of understanding is to start planning out your human machine, and understanding how to represent it in 3-dimensional space from a fixed viewpoint.  Start simple.  Start with what you understand.  When you find a gap in your understanding, look for an answer.  When you find a discrepancy between your mental machine and the model or a piece of reference, adjust the design for your machine accordingly.  Let your machine evolve along with your understanding.  As it does, you'll find both drawing from the figure and from imagination much less mystifying.

Tuesday, February 16, 2010

Perspective and the Figure - Part 1

This is based on a post I wrote over at a few months ago.

Realistic drawing in the Western tradition is dependent on the idea of a fixed viewpoint and the relation of all forms in the picture plane to that viewpoint. This is really what perspective is. Imagine a box facing you at eye level- you will only see its front plane. Move it straight to one side and you will see its side plane and its front plane. Move it straight down from there and you will see the top, side, and front planes. But then, if you keep it in that same location but rotate in certain ways, you might only see its front plane again.

This, combined with the idea of diminishing, is the heart of perspective. The exact implementation of this is all the vanishing points and horizon lines and eye levels and all that. While those things are very important to know, they're really secondary to this idea of the fixed viewpoint*. When you're drawing the figure, it's too complicated to figure out most of the vanishing points- you have to understand the first part well enough to estimate the effects of perspective on a given form. Figure drawing pretty much boils down to a complicated puzzle involving the cube example from above for each form of the body- but each form is much more complicated than a box. These forms change shape based on muscle flexion and forces from the environment, and are oriented in complicated ways dictated by the joints of the skeletal structure. Just take the most basic pose: a person of your height standing straight up facing you, with their eyes at your eye level. You will see the tops of their feet and shoulders, but not the top of their head.

Along with studying buildings and the other usual suspects in perspective, practice the simple rounded forms (cylinder, cone, sphere) bounded by a box from every possible angle, then move on to more complicated forms like vases. Really understand how each form fits within the box, and what happens to the ellipses in all possible cases. Then move on to more complex assymetrical forms with cross-sections that aren't circular. Most people blow this off thinking they understand it, but strangely can't draw a proper cylinder and unsurprisingly can't draw a figure except for a few static & memorized poses. It's easy to understand but hard to do properly.

The idea is to work out all the scenarios carefully ahead of time, so that when the model is in front of you don't need to spend time figuring it out then and there. What is a calf but a strangely shaped vase? And if you can't draw a simple vase tipped toward you in perspective without a lot of headache, how are you going to get the job done with the model in front of you (and probably with much less time)?

Spend the time up front and get these perspective scenarios into your vocabulary, so you're able to use them "conversationally" while drawing. It's important to be able to think this way, but not be mechanical about it.

* I recently found Bruce MacEvoy's excellent (but technical) articles on perspective over at, and was pleased to see that he explicitly breaks out the Stationary Viewer as the first step in creating a perspective view.

Saturday, February 6, 2010

Quick & Dirty Division

Dividing things visually is pretty critical for drawing- a teacher of mine used to go so far as to say "Drawing is division".  When doodling in your sketchbook, it's easy to start with a head, maybe add a torso, and if you feel like it (and there's still room on the page) you can throw in some legs.  But when you start thinking compositionally, you need to be able to say "The figure goes here".  That is to say, it needs to fit within a certain spot on the page or the greater composition in order to create a good whole.

When it comes to that point, it's critical to start thinking in terms of division.  Unfortunately, humans are pretty terrible at dividing anything other than in half- and they're not very good at that over large distances.  Head lengths, a common proportional device, fail us pretty quickly.  Unless the figure is 8 head-lengths, which is convenient for division, we can't divide our composition space into some weird number of head lengths that most people are (7.5, 6, 6.5).  Proportional dividers and grid transparencies can help with this, but sometimes they're too cumbersome to deal with- especially in quicker poses or when working on larger surfaces. 

Plus, all of this is assuming a nice standing figure with little foreshortening.  If the model is crouching or reclining, head lengths pretty quickly become useless- even with the proportional divider.  In such a case, or if the pose is quick or you don't want to use too many aides in your drawing, you can use this technique to quickly find a halfway point of something.  It works on both the model and on your drawing.  All you need is a straightedge, which a relatively straight pencil, brush, piece of charcoal, or knitting needle can function as just fine.

  1. Choose a top and bottom point.  If it's your drawing and it's in the beginning stages where there aren't many marks on your page to grab on to, make a small mark at the top and bottom.
  2. Estimate a halfway point.  Don't labor about it- just take your best guess.  It's most likely going to be wrong, but it will help us quite a bit nonetheless.  If you're measuring on your drawing, put a very faint mark where you think halfway will be.  If you're looking at the model or some other subject matter, just choose some landmark on the subject.
  3. Extending your arm all the way and locking your elbow, take your straightedge and put the end point at your estimated halfway point.  Slide your thumb down so it lines up with the bottom mark that you made or decided upon.
  4. Keeping your arm extended and your elbow locked to minimize forward and back movement, shift your arm up so the end point is now at the top mark.
  5. Unless you made a very good estimate, your thumb should be above or below your estimated halfway point.  Here's the key- halfway between your thumb and the estimated halfway point is the actual halfway point.  Since it's a much smaller distance to work with now, you can now estimate a new halfway point based on this new information, which will be significantly more accurate.  If you're looking at the subject, find a new landmark to hold on to mentally.  If you're measuring on your drawing and there's nothing on the page to grab on to, make a new mark on the piece
  6. Keeping the end point of your straightedge aligned with your top mark (or putting it back there if you used your straightedge to make a mark), slide your thumb the new & improved estimated halfway point.
  7. Because we're human, it's good to check out our estimations.  Small shifts in our position can make a big difference, as can things significantly above or below our view point.  Further, ssuming something is correct that is slightly off can be the death of proportions.  The beauty here is that to check things out, you simply have to repeat the process. Go back to step three and repeat until you're satisfied. On a quick drawing I might do this process only once, but on longer drawings I might repeat it several times.
It's important to note that this process- or any measuring technique- will only get you so far.  They sound really good on paper, but they are never as accurate as they might seem.  Most people go through a phase when they begin to understand such techniques where they become overly dependent on them.  They try harder and harder, but still things don't line up.  While there is a certain degree of meticulousness that will bring results, it doesn't seem to be a silver bullet.  It's best to supplement this kind of measuring with other kinds of proportional systems, especially constructive systems.  I tend to use such measuring just to get me in the ballpark, or to cross-check other proportional estimates.