Cartoon-Style Character Animation

8/8/2019 Cartoon-Style Character Animation

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KNOCK HIS BLOCK OFF

By Jim Armstrong

Contributing Writer

Cartoon-style character animation involves more than just toon shading. Characters often haveexaggerated features and motions. Many exaggerations do not seem to fit the structure imposed by

Character Studio Bipeds. Biped structure and dynamics, although flexible, are based upon realistic

humanoid motion. This tutorial illustrates how to combine Physique with other MAX modifiers to bend

(and in some cases break) that reality.

3DS MAX 4.2 and Character Studio 3 are used for this tutorial. An intermediate-level understanding

of MAX is required. You should understand the basics of working with Character Studio, including how t

create/modify Bipeds and use facilities in the Motion panel to set keys. You should understand the basics

of the Physique modifier.

Important terms and MAX interface elements are highlighted in bold type.

Introduction

3D Stickman

One of the hottest animations in the Flash industry (at the time of writing) is

the Stickman fighting movies by XiaoXiao. The fast motion and slapstick

action is both entertaining and comical. The original movies were drawn by

hand, frame-by-frame, with light tweening applied in Flash. The latestversions (installment #8 is the most current at time of writing) employ a

mixture of rendered 3D objects and hand-drawn stick-figure characters.

As a martial arts action fan, I decided to take this concept to the next logical

level -- 3D sets AND 3D characters. Although a 3D stick-figure character

presents no modeling challenge, the style of animation involves some

exaggerations outside the normal application of Character Studio.

Cartoons often exaggerate reality to extreme levels in an attempt to generate

maximum humor from the animation. Characters flex muscles that are tentimes larger than normal proportions or have limbs stretch to highly

unrealistic limits. Eyes will bulge to twice the size of the head. Of course,

we all get a good laugh out of these situations -- that is the purpose of the

effect.

The 3D Stickman character is introduced in the context of a short fight

sequence. In the middle of the screen, 3D Stickman is rushed by two other

fighters, one from each side. The fighter to his right has a lead pipe in hand

and is met with a solid right side kick. As soon as 3D Stickman pulls out of

the side kick, he rapidly turns to execute a right spin kick to the head of thefighter approaching from the other side. In the process, he knocks the
http://www.3dcafe.com/asp/platinumdefault.asp


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oducing 3D Stickman

, this guy won't be winning any character modeling awards :) The head is modeled as a box since that object renders to .SWF format with fewer espective view of a sphere renders as a circle that requires more 'curves' in Flash to represent than a box. The difference in file size is small, but atr the course of a several-minute animation, it really adds up. Since the animation is destined to be web-based, anything that can be reasonably duce file size is helpful.

torso box has a higher poly count so that the Biped Spine links can be used to bend and twist this bodypart.


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KNOCK HIS BLOCK OFF

By Jim Armstrong

Contributing Writer

Physique Part I

At first, it seems that the discussion of the Physique modifier for such a simple character is a waste of

time. For beginners, going through this exercise provides a fully articulated character that can be used to

test the application of mocap and .BIP motion files, motion flow editing, and other advanced Character

Studio features without the tedium of rigging more complex characters.

We will also see how to exploit limb disparity in the character vs. the rig to enhance the comic appearance

of the character.

To begin, a Biped was created that matched the height of the character. The following Structure settings

were used:

Neck Links: 1

Spine Links: 4

Leg Links: 3

Ponytail 1 Links: 0

Ponytail 2 Links: 0

Fingers: 1Finger Links: 1

Toes: 1

Toe Links: 1

Four Spine Links were used to apply bending and twisting to the torso geometry. While part of the

character appears very rigid, the torso section can exhibit some element of flexibility. This apparent

contradiction can be used to enhance the cartoonish behavior of the character.

Finger and Toe links were added to allow for minor motion at the hand/foot extremities. If you do not

wish to add such capability, the Biped could be created with no fingers/toes and no finger/toe links.

This character is comprised of fourteen independent bodyparts -- a head, two segments per arm, two

hands, a torso, two segments per leg, and two feet.

It is tempting to select all the boxes, then apply Physique in one step. This can cause problems in

envelope settings at a later point. It's similar to applying Physique to a group. We don't want to group the

objects into a 'single' character. Instead, each object is to be independently controlled with no linking or

influence from any of the other body objects.

The collection of boxes is held together in a form representing a character by applying Physique to eachbox and initializing the modifier with the same Biped.


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nitializing Physique close

t's easy to fall in the habit of always using defaultarameters when initializing Physique. We can preset these of Rigid envelopes and set Blending to two links indvance. 1 Link would be appropriate for the most basic

nimation of this character. Two links are used for reasonso be discussed in a subsequent section.
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ht Forearm Link and Envelope Settings

default forearm envelopes provide complete influence over the box vertices representing the character's right forearm. The Biped RperArm link is turned off, having no influence on that geometry. The same is true for the Hand link.


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KNOCK HIS BLOCK OFF

By Jim Armstrong

Contributing Writer

Torso

Pelvis Envelopes

click to enlarge

Although most of the character's motion is completely rigid, a few

modifications were made to the geometry and rig to provide for some slight

exaggeration. The box representing the torso was given a much larger poly

count. Instead of one link influencing the torso, it is influenced by the Biped

Pelvis and each Spine link.

As the COM rotates while feet remain planted, the box twists at the lowerextremity, providing the appearance of wider 'hips' at the bottom. As the

Spine links bend, the torso appears to bend as well. This is particularly

noticeable with Bend Links mode activated. The mixture of fluid and rigid

motion enhances the comical appearance of the character.

The Pelvis envelopes are illustrated in the adjacent thumbnail image. The

boxes indicate the range of influence of each Spine link. In this particular

screen shot, the character has been moved into an intial pose that is used to

illustrate a point in the next section.

The Neck and Clavicle links have no influence over the torso. Those links

are turned off. The same is true for the Upper Leg links.

Upper Arms

Clavicle Influence on Upper

Arm

In this character, there is not a 1-1 match between Biped links and

bodyparts. For example, the Stickman character has no clavicles, only an

upper arm segment that is disjoint from the torso.

One of the features I wanted to add to the character was some natural squash

at one or more joints. For example, as the arm moves up and down, it would

appear to be thinner at the shoulder joint than at the elbow. The same

appearance could be applied to the upper legs. This would appear to

exaggerate the forearm during arm motion without bulging the forearm box

(that did not have the poly detail to support bulges in the first place).

The squash is accomplished by allowing the Clavicle link and the

UpperArm link to both influence the upper arm vertices nearest theshoulder Blending is set to 2 Links during Physique initialization


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orso - Spine and Pelvis Link Influence close

The Pelvis envelopes are illustrated above The red boxes indicate the area of


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avicle Influence on Upper Arm

th the Clavicle and UpperArm links influence the Box vertices closest to the shoulder. As these two links movendem, the edge of the Box at that joint area remains relatively constant. If the UpperArm link moves while theavicle remains fixed, the box tends to squash at that joint. This makes the forearms look relatively large duringtreme arm movements without applying a bulge to the forearm.

e same technique can be used to play the Forearm/Hand links and Pelvis/UpperLeg links against one another tvariety of comical appearances to character motion.


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Clavicle Influence on Upper Arm close

s illustrates the effect of no Clavicle influence on the upper arm. Compare the two box edges. In this rig, the upper arm over-rotates. Thismpensated for by shortening the Clavicle length and increasing the UpperArm length.


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KNOCK HIS BLOCK OFF

By Jim Armstrong

Contributing Writer

Side Kick

Apex of Side Kick

click to enlarge

Keyframing the side kick - spin kick tandem was discussed in detail in the

Martial Arts Action tutorial. This section illustrates the scene setup and a

couple key points during the action. This leads up to the point where one

fighter's head must be literally separated from the body.

After rigging, the Biped and character bodyparts were cloned twice to create

the other two characters in the intro. shot. The central character was given adark-colored texture (remember the Chuck Norris movie, 'Good Guys Wear

Black?') . The other two fighters were given light-colored textures for

contrast. In order to quickly isolate the heads of each character, the colors (in

the viewports) for the geometry were changed.

One of the fighters has what appears to be a lead pipe in hand. The pipe is a

simple cylinder controlled by a Link Constraint. Up until the point where

this character is kicked, the pipe is linked to the Biped R Hand. At the apex

of the kick, the character bends forward from the impact and starts to drop

the pipe. The pipe object is then controlled by a Dummy helper and fallstowards the ground.

The apex of the side kick is illustrated in the adjacent thumbnail image. All

three characters in this scene use the same bodypart geometry and the same

type of rig. Notice how the torso geometry bends forward, responding to the

impact of the kick. If the torso had been rigged to be entirely rigid, the

character could have bent forward at the pelvis, but the effect would not

have been as impressive.

Spin Kick

Apex of Spin Kick

Immediately after the side kick, the first fighter's crumpled body drops to the

ground. The second fighter moves into camera view and is met with a spin

kick. This is illustrated in the adjacent thumbnail image.

The movement from side kick to spin kick is rapid. As 3D Stickman

recovers from the side kick, his head spins around to see the other fighter.

The arms and torso whip around, ahead of the lower body. The body bendsdownward as the lower body and right leg whip around to the complete the


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pex of Side Kick close


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pex of Spin Kick close

Mr. Purple is already out of commission. Mr. Blue is about to lose his head --terally!


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KNOCK HIS BLOCK OFF

By Jim Armstrong

Contributing Writer

Linked XForm

Linked XForm

click to enlarge

One of the reasons the characters were created from separate bodyparts is to

allow for independent animation of each section of the body. The Biped is

used to maintain a structured relationship between each independent

segment. That structure happens to fit the form of a bipedal character.

As the Biped moves, Physique constantly influences the head geometry. At

first, it seems difficult to move the head independently of the remainder ofthe body. Animating the head or linking it to a dummy often results in

undesired effects. The head may appear to move as desired when setting

keys, but snap back in place during playback.

A Linked XForm modifier was added to the stack to pass the results of the

Physique modifier to another object, known as the control object. In this

scene, the control object is a Dummy helper named headControl. After

applying Physique to the head vertices, PRS animation of the control object

is added to the motion.

Applying Linked XForm is very simple. It is important to assign the control

object at frame 0 for an animation. This was done for the current scene.

After applying the modifier, there is a single control in the Parameters

rollout. This control allows you to pick the control object. The adjacent

thumbnail image illustrates the stack for the head geometry of the fighter

who is about to lose that head :)

Now, we can animate the character's head by offsetting Physique motion

with translation and rotation of the control object.

Animating the Control Object

In order to achieve the desired motion, the headControl object should

remain stationary from frame 0 until the impact frame (frame 38 in this

scene). From there, it moves in short increments (few frames between

keyframes) to offset motion in the Biped Head link.

A Linear Position controller was assigned to the Position track of theheadControl object in track view Since it is not necessary to control the


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nked XForm

dd the Linked XForm modifier in the stack after Physique. Scrub the time slider to frame 0, then as

e control object. In this scene, the headControl Dummy helper serves as the control object.


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rol Object Motion Just After 'Impact'

e how motion in the control object offsets movement in the Biped Head link. If the motion was an exact offset, the box representing the fighter's head would appear to reonary. Additional motion in the control object allows it to appear as if the head has been literally kicked off. 3D Stickman bobbles the head, then balances it on his hand iation.

unrealistic animation, yet easily accomplished even within the confines of Character Studio, a tool designed for 'realistic' animation :)


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KNOCK HIS BLOCK OFF

By Jim Armstrong

Contributing Writer

Final Animation

Flash Animation

click to enlarge

If you have the Flash 5 player, you may view the entire intro. animation

(minus some of the production visuals and sound). Although the

presentation contains a preloader, there is no 'replay button.' Right-click and

use the 'Rewind' and 'Play' options to replay the animation.

Notice at the end of the intro, when 3D Stickman is turned slightly to one

side, the bottom of the torso is slightly flared.

Summary

Beginning character animators are often lead to believe that character geometry is continuous. This

animation illustrates how fourteen boxes are arranged to provide a 3D representation of a simple stick

figure. The CS Biped provides structural control and organization. The independent nature of each

bodypart allows any section of the character to be separately animated with Linked XForm (and possibly

other modifiers).

Some types of cartoon-style animation can be achieved by using two or more Biped links to control

sections of a bodypart. Squash at joints can be achieved even with Rigid envelopes.

While the Stickman geometry is incredibly simple, some of the animations that can be performed with this

character are far from simple. We will return to this character and more martial arts action in future

tutorials. In the mean time, do not be deceived by the simple nature of the character. As Bruce Lee said in

'Enter the Dragon,'

"It is like a finger pointing towards the moon. Don't concentrate on that finger or you will miss all that

heavenly glory."

I hope you find some of these techniques useful in future projects.

1 | 2 | 3 | 4 | 5 | 6

2002 Platinum Pictures Multimedia, Inc.


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ash Animation c

his movie requires the Flash 5 player. Although a preloader is employed, there is noeplay' button. Right-click and use the control options to first rewind the playhead, thenlay.

Cartoon-Style Character Animation

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