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TUTORIALS Animal anatomy tips Is this winged liona flight of fancy? Notreally: if you understandthe anatomy of an animal,any creature you makewill be believableTIPS & TRICKSAnatomical perfectionGetting under the skin of an animal will help you to better express form andBY SCOTT EATONposture, and enable you to realise more accurate rendersOur expertthis issue Every character and concept artist should studyto accurately articulate the model: where the joints are, whatanatomy. Why? Because without a soundmasses deform and what masses remain rigid. Finally, theknowledge of anatomy, your creations will lackanimator takes the rig and works within the constraints laidcredibility. And if you are working in a creaturedown by the skeleton and controls. If knowledge is lacking inpipeline, an understanding of the fundamentals isany of these waypoints in the pipeline, then the final resultabsolutely essential.is compromised. 3D imposes more demands than any otherAt the top of the pipeline, the concept artist illustrates thefinal form of the creature. Of course, not everything can beconveyed in a single or even multiple drawings, so the modellerScott EatonA traditionally trained artistwho runs the artistic anatomyprogramme at Escape Studios,Scott Eaton has taught at andconsulted for many top gamesand postproduction houseswww.escapestudios.co.ukmedium, because very little information can be left out: weneed to know it all.The task is difficult given the tremendous variation theremust pick up the pieces and interpret, adding his own artisticis in the animal kingdom: from hippopotamus to mouse totouch to the concepts. It is critical for the modeller to be abledinosaur. The important thing is to study and understand theto accurately interpret the concept art and, where necessary,commonality between them. Once this is understood, thecorrect or add to the anatomical forms that are being built invariations become simple to grasp. Likewise, once the basic3D. Modellers must understand the underlying structure andstructures are understood, they can easily be extended tomuscles that create the masses and planes of the animal.imaginary creatures, grounded in functional anatomy that isEqually, the rigger needs to understand the same informationlearned from the diversity of nature.062 3D WORLD April 2007TDW89.t tips 0628/2/07 16:45:16
Animal anatomy tips TUTORIALSIN FOCUS Human versus quadruped anatomyHumans and animals have striking similaritiesbetween their anatomy. The most effectivestarting point for studying animal anatomyis to study human anatomy first.With a firm grounding in human anatomy,the anatomical variations among animalsare easy to spot and commit to memory. Forexample, the forearm muscles of a dog mightseem a daunting tangle of thin extensor andflexor muscles, but they correspond exactlyto the flexors and extensors in a humanforearm. If you know the human forearm,the forearm of a dog is only a simple changeof proportions.If we extend this example and considerhorses, we know that they don’t have multiplefingers (or toes), but a set of single bones thatcorrespond to human finger and metacarpal(hand) bones. Also horses have evolved torestrict the movement in their wrists to justa forward and back swinging motion, givingthem great speed and stability in their frontlegs. These two adaptations have eliminatedthe need for a number of forearm musclesthat are common to man, felines, and canines. The drawing above shows a human and dog forearmside by side. Because dogs have the same forearmbones and digits, the muscles also match The hamstring muscles of the horse are highlighted and the insertionis located (it generally spans over the nearest joint)CREATING A BODY PLANthe upper versus lower arm; the location of the point of the shoulderThe body plan is a simplified representation of the major massesrelative to the bottom of the ribcage; the relative height of theand joints of an animal. Understanding the body plan of a subject iselbow versus the knee; and the length and angle of the neck.the place to start when drawing, modelling, rigging or animating anunfamiliar animal. Simply, the body plan is a schematic diagram of anSKELETON: RIBCAGE AND SCAPULAanimal in profile, which blocks in the masses of the ribcage, pelvis,If we compare a human torso with an animal torso, we find thatand skull in relation to each other.they are remarkably similar. Mostly only their proportions and shapesA schematic representation of the front and hind legs is laid overchange, but there are some critical differences in the ribcage andthe top of the rib cage and pelvis. The masses of the limbs can bescapula (shoulder blade). For a start, the ribcage in quadrupedssimply represented using boxes. Usually a single dot is used at eachtends to be narrow side to side and deep top to bottom, thejoint to locate the point of rotation.opposite to the wide ribcage found in humans. Also, the narrowEstablishing the body plan of an animal is a quick way to graspthe large proportions that are characteristic to individual species.sides of the ribcage found in animals make a perfect sliding surfacefor the scapula. And because quadrupeds lack a clavicle (collarbone), the scapula has a wide range of motion over the side of theEVERYTHING SHOULD BE IN THECORRECT PROPORTIONribcage. A human’s scapula slides along the back of the ribcageProportions work hand-in-hand with the body plan and establishform allows the scapula to advance the entire front leg as it movesthe overall shape of the animal’s body. Similar to proportionalforward, and then slide upward and backwards as the leg takes thesystems for humans, the length of the skull can be used to measureweight of the body.and is constrained by the clavicle. This sliding in the quadruped’s The shoulder girdle of a lion:note the angle of the scapulaand humerus. The triceps, thedominant muscle of the upperarm, lies between the body ofthese two bonesthe large proportions of an animal’s body, helping to position criticalmasses and landmarks.Critical measurements to consider are: the length of the ribcageAs the name suggests, a quadruped uses four legs to move around,and the pelvis is adapted for locomotion on four legs. Unlike humans’ relative to the overall length of the body; the relative length ofSKELETON: PELVIS AND TAILApril 2007 3D WORLD 063TDW89.t tips 0638/2/07 16:45:22
TUTORIALS Animal anatomy tipsnearly vertical pelvis, a quadruped’s pelvis takes on a large forwardlean. This inclination helps to transmit the locomotive force of hindlegs into the spinal column and onto the mass of the front of thebody. When studying a species that you are not familiar with, makenote of the angle and the bony points of the pelvis. Combined withthe tail, this mass establishes the profile of the hind quarters.RANGE OF MOTIONThe major joints of the skeleton of any quadruped function verysimilarly to those of a human bent over and walking on fingers andtoes. If you keep this in mind when you are establishing the directionand range of motion of your joints, it is hard to make a mistake. Theelbow of an animal always opens to the front just as in a human,and the knee always opens to the back, making the shape of twoopposing parentheses, like so: ) (Because the scapula is free floating on the side of the ribcage– held in place by a system of muscles – the entirety of the frontleg can slide forward, back, up and down. Therefore any rig that youbuild should reflect this range of motion. This sketch show the variation of bodyplan between species. Notice how fairlysmall and simple changes in proportionresult in entirely different speciestheir arms, palm up, so the biceps – a prominent muscle on humans– becomes a minor shape on an animal’s front leg. The triceps,however, bear the continuous load of walking, standing, runningand jumping and are therefore powerfully developed, creating theDISTRIBUTION OF THE UPPER ARMSHow are the masses of the upper arm distributed in quadrupeds?Functionally, quadrupeds have little requirement for lifting withdominant mass of the upper front leg.We locate the mass of the triceps by looking at the underlyingbones. The bone of the upper arm (the humerus) projects backwardsIN FOCUS An écorché approach to animal anatomyOne of the best ways to study anatomy – be it human or animal – is bya process called drawing in écorché. It’s the French word for ‘flayed’, but ithas become synonymous with the technique of drawing or sculpting figureswithout skin.The process is simple in concept, but not nearly as easy as it sounds.Start with a good reference image that has enough contrast to highlight somelandmarks and muscular definition. Overlay a piece of tracing paper, or adda blank layer if working digitally, and begin your detective work.Locate any bony points or landmarks that can serve as a reference pointfor locating muscle masses. Draw in the outline of the muscle group, takingits origin, insertion and volume into account. And finally draw in the fibresof the muscles. Reference anatomy plates as often as you have to. You mayfind that you need to use these frequently in the beginning, but as yourknowledge increases you will be able to complete entire images withoutexternal reference.It is often instructive to draw from an image of a sculpture or painting byan old master who was knowledgeable in animal anatomy. Two of the best areGeorge Stubbs, a 17th-century English painter of horses, and Antoine-LouisBarye, an 19th-century French sculptor who made his reputation sculptinganimals. Equally, drawing écorché images from the plates out of An Atlasof Animal Anatomy by W Ellensburg (see Further Reading at the end of thisarticle) gives you a chance to directly compare the skinned versions of theanimal with the anatomical plate in the same pose. Animal painter and anatomical draftsmanGeorge Stubbs created écorché drawings similarto this one, which shows the muscles on thechest and shoulder of a horse064 3D WORLD April 2007TDW89.t tips 0648/2/07 16:45:27
Animal anatomy tips TUTORIALSfrom the shoulder at an angle, sometimes as much as 45 degrees.The scapula also continues along back from the shoulder at anangle. Together they create a closed angle for the mass of thetriceps to sit. Usually one head of the triceps – a three-headedmuscle – lies directly on the humerus; the others fan backwardsand attach onto the scapula.ADDING SOME MUSCLE TOTHE HAMSTRINGSAn animal’s legs have a similar set of muscles to our own, butbecause of functional differences, the proportions are entirelychanged. In animals, the hamstring muscles are the dominateleg mass when viewed from the side; in humans, the quadriceps Écorché drawing showing themuscles in the legs of a horsedominate in profile. In humans, the hamstrings insert at the top ofthe lower leg, just below the knee. But in animals, the hamstringsinsert anywhere up to two thirds of the way down the lower leg.Functionally, this helps quadrupeds to powerfully drive the legbackwards when running.PINPOINTING THE BONYLANDMARKS The overlay on thisdrawing shows the locationof the bones and joints ofthe legs. Remember theelbow opens to the frontand the knee to the rearBony points, the places where the skeleton is directly underthe skin (subcutaneous), should be located on your models andused as reference points to place the muscles and establish theproportions of the subject’s body. As the bony points are locatedwhere the skeleton lies straight under the skin, they shouldn’tdeform when rigging: they should only move rigidly with the joint.The most important landmarks are: the spine of the scapula;the elbow; the front point of the pelvis (iliac crest); the rear pointof the pelvis (ischium); the knee (patella); and the heel bone.Once these points are resolved on your model, the process ofplacing the muscles masses becomes nearly trivial. In some ways,it is like connecting dots: first, find the origin of a muscle andrelate it to the nearest bony landmark; next, identify the insertionof the muscle, which generally spans over the nearest joint; finally,place the body of the muscle over the bone using these twopoints as reference. Understanding the muscular attachments willhelp you to determine the direction of the pull of the muscle.April 2007 3D WORLD 065TDW89.t tips 0658/2/07 16:45:31
TUTORIALS Animal anatomy tipsNATURAL SELECTIONAn animal’s form and function cannot be separated from theenvironment in which it exists. The kangaroo, for example, evolvedits hop as an energy-efficient means of traversing the arid climateof Australia. The hopping mechanics are created by an extremelyelongated lower leg (tibia) and lengthened foot bones (metatarsals).Combine these proportions with an extremely resilient Achillestendon and calf muscle, and the result is powerful leg thrust. Usethese amazing adaptations of nature as inspiration when imaginingyour own creatures. An example of an écorché drawingcomposited over a bronze sculptureby French romantic artist AntoineLouis Barye. It is instructive to be ableto work from two different views,such as this one and the one belowSPEED AS RELATES TO PROPORTIONA quick inspection of the body plan of a horse versus an elephantreveals a little bit about how certain animals have evolved for speed.Fast, efficient runners tend to have muscles masses on or near thetrunk and pass the force of the muscles down long slender bonesvia tendons. Of course, certain cats and dogs are extremely fast, but The skull, made up of two parts – the craniumand the mandible – supports the structures ofthe face and protects the brain against injurytheir speed relies on power over a short distance and is less efficientbecause of the distribution of weight along the legs.HANDS AND FEETThe hands and feet of animals are analogous to our own in thatSTUDYING THE SKULLthey have wrist and ankle bones, foot and hand bones, and fingersThe skulls of animals share a common structure. They have evolvedand toes. The numbers and proportions of these bones varyto protect the brain and give a secure housing, for the sensorydepending on species. Dogs and cats walk on four fingers and fourorgans (eyes, nose, ears, and mouth), and also to allow animals totoes, with their hands and feet elevated off the ground. Hoofedeat whatever their diet dictates.animals, called ungulates, like horses or deer evolved one or twoThe widest part of the skull is established by the cheekvery strong, elongated metatarsals, with their last finger digitsbone, called the zygomatic arch. The arch starts from the bottombecoming their hooves. Other strange ungulates have three or fourof the orbit, below the eye, and spans backwards to the ear. Ittoes like rhinos and hippos respectively. never appears as an arch in life, because the powerful muscle ofmastication (chewing) fills in underneath and below the arch, givingmany animals muscular-looking jaws.Forward of the zygomatic arch and the orbits are the nasalbone and the mandible (lower jaw). The projection of these twoFURTHER READING Best books on animal anatomyskull bones establishes the length of the skull in profile, which, inturn, dictates the shape of the muscle. Variations in these majorstructures establish the main differences between heads ofdifferent species. An example of an écorché drawing composited over a bronze by Barye.Once the form of an animal is understood, muscle groups fall into placeHow to Draw Animalsby Jack HammISBN: 0-399-50802-3 Fantastic introductory bookthat explores the forms of manydifferent kind of animals Packed full of useful info relatingto different speciesAn Atlas of Animal Anatomyfor Artists by W EllensbergISBN: 0-486-20082-5 The classic reference for animalanatomy plates However, there’s very littletext and gives no explanationof functionAnimal Anatomy for Artists,the Elements of Form byEliot GoldfinderISBN: 0-195-14214-4 Comprehensive classification ofall muscles for a variety of species Best resource for studyingcomparative anatomyThe Anatomy of the Horseby George StubbsISBN: 1-83468-003-3 Master anatomical plates invarious stages of écorché Accompanying text is reprintedin the back of the book. It is tiny,and very difficult to readThe Artist’s Guide to AnimalAnatomy by Gottfried BammesISBN: 0-486-43640-3 Abbreviated version of the longerGerman original Excellent schematic drawingsof animal skeletons andmusculatureAnimals in Motionby Eadweard MuybridgeISBN: 0-486-20203-8 Sequential photographscapturing animals at variousstages in their gate. Valuable reference for riggersand animators066 3D WORLD April 2007TDW89.t tips 0668/2/07 16:45:37
the anatomy of an animal, any creature you make will be believable very character and concept artist should study anatomy. Why? Because without a sound knowledge of anatomy, your creations will lack credibility. And if you are working in a creature pipeline, an u
