Table Of ContentCHAPTER 1
Arcs – Organic Movement/
Natural Motion
Very few living organisms are capable of moves that have a mechanical in and
out or up and down precision.
The Illusion of Life: Disney Animation – Frank Thomas and Ollie Johnston
In this chapter, we’ll be looking at the basis of natural movement – arcs.
Arcs are present in the majority of motions in the natural world; this is due
to the effects of mass, weight, and inertia on objects, whether living or not.
Think of an object traveling through the air, such as a ball being thrown;
although the ball may follow a straighter line at the start of the throw, it will
naturally follow more of an arc, as it loses speed and gravity takes hold. The
natural phenomenon of arced motion needs to be replicated convincingly in
animation to add believability, if the motion is not arced or the timing is even,
it will look unnatural and the illusion will be lost.
Natural arcs can be seen in the animation exercises throughout this book. The
following are some examples where you would see arcs in motion in the other
tutorials exercises:
Tradigital Maya. DOI: 10.1016/B978-0-12-385222-9.00001-9
© 2012 Elsevier Inc. All rights reserved. 1
Tradigital Maya
Bat Swing – In the baseball bat swing animation that we’ll look at in later
chapters, a clear arced motion can be seen on the swing; this is because the
bat swings from the wrist, which is a fixed pivot on the hand. This pendulum
type motion is typical in human or organic motion and also applies to the
limbs on the body (see Fig. 1.0.1, left screens).
Jump Landing – In the jump animation that we’ll look at in Chapter 11,
there are natural arcs on the body throughout the animation, from the start
through the motion in the air and on the landing. At the landing phase of the
sequence, the body pivots around the foot that’s planted on the ground, with
natural arcs visible on the hips and torso (see Fig. 1.0.1, third screen from left).
FIG 1.0.1 Arcs – bat pendulum
swing, hip rotation, and body pose.
Character Posing – Organic arcs are also visible in the body’s form and shape in
real life, even when the body is not in motion. This is due to the curvature of
the spine and weight distribution on the body. Typically, the body distributes
weight off center, which creates natural arced shapes running across the body
(see Fig. 1.0.1, fourth screen from left).
If the body is posed with purely straight lines or blocky square shapes, the
pose will look unnatural and robotic. This is something, which is common in
many novice animations. Throughout the book, we will look at how to pose
the body with natural arcs that give the animation weight and balance. We
will look in detail at character posing specifically in Chapter 9.
Arcs in Object Motion
In the first two tutorials in this chapter, we’ll look specifically at arced motion
for object animation. As in the jump animation example that we touched on,
objects moving through the air should have a natural fluid arced motion due
to momentum, inertia (or loss of speed), and the effect of gravity.
Ball Bounce – In the first tutorial, we’ll look at a ball bounce animation. Arcs
are apparent in the motion in both the timing of the animation as the ball’s
momentum is lost and in the motion as the ball bounces across the ground
(see Fig. 1.0.2, left screens).
Plane Trajectory – In the tutorial of Chapter 2, we’ll look at a takeoff animation
for an F16 fighter plane. Although the F16 fighter is being driven into the
air by the rocket jets on the plane, there are still natural arcs that should be
apparent on both liftoff (due to momentum and gravity) and flight as the
plane maneuvers (see Fig. 1.0.2, right screens).
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Arcs – Organic Movement/Natural Motion
FIG 1.0.2 Arcs – object trajectory.
Localized Arcs – Human Motion
The third and fourth tutorials in this chapter will focus specifically on arcs
in human motion. For these exercises, we will look at arcs on a couple of
localized areas on the body. These tutorials will introduce common character
animation concepts including posing and Inverse Kinematics.
• In the arm swing tutorial, we will look at the pendulum swing on the arm;
in addition to analyzing the arc on the arm swing, we will also touch on
a couple of other principles of animation including follow-through and
Ease In & Ease Out to mimic real-world motion through animation (see
Fig. 1.0.3, left).
• In the run cycle tutorial, we will look specifically at the arc on the hip
trajectory in the animation. The natural arc of the hips during the weight
shifts and foot plants on the run is key in creating believability in the run
cycle (see Fig. 1.0.3, right).
FIG 1.0.3 Arcs – localized human
motion.
Chapter 1.1 – Animation Test – Bouncing Ball
The bouncing ball animation test was originally used at Disney as a test of skill
for new animators joining the studio. The test is still in use today at studios
including Pixar:
no matter how seasoned you are, this is the first thing that an animator
would do when they come into Pixar, because it shows timing, spacing,
squash and stretch, anticipation, etc.
Andrew Cordon, Senior Animator, Pixar – 3D World Issue 130, June 2010, p. 24.
In this tutorial, we’ll be focusing initially on creating fluid blocked in
movement for the ball bounce through the standard manipulation and hand-
keying tools in Maya. The tutorial will first introduce you to the fundamentals
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of creating and editing animation in Maya including the following: Animation
Preferences, the Channel Box (for viewing motion values) Transformation tools
for manipulation, keyframing, and playback controls (see Fig. 1.1.01).
FIG 1.1.01 Animation basics –
Transform Tools, Channel Box,
Keyframes, and Orthographic View.
Other key animation principles including Ease In & Ease Out, Squash and Stretch,
and Timing & Spacing will also be introduced with the use of key edits using the
Time Slider, Channel Box, and Maya Graph Editor to edit motion timing. The Maya
Motion Trail feature will also be utilized alongside display ghosting to validate the
final arc on the ball bounce as well as the timing intervals (see Fig. 1.1.02).
FIG 1.1.02 Animation ghosting,
the Graph Editor, and Motion Trail.
Animation Preferences
For our animation of the bouncing ball, we’ll work on an initial bounce cycle
that can be looped. For a ball bouncing, this would be less than 1 second, with
the time varying based on the height of the bounce and mass of the ball.
For the length of the animation sequence and playback rate, this can be
set from Maya’s animation preferences. Let’s take a look at how to set up
animation and playback range within Maya:
• Open a new session of Maya or select File > New Scene to clear the current
scene.
• The preferences for Maya’s frame range can be set from a few different places:
• Animation Preferences button – This is at the bottom right corner of
the user interface; it is the small white icon with figure in red beside
the key icon (see Fig. 1.1.1, top left screenshot). Clicking the “Animation
Preferences” button will automatically open Maya’s “Preferences” window
to display the “Time Slider” options (see Fig. 1.1.1, middle screenshot).
• Window > Settings/Preferences > Preferences (see Fig. 1.1.1, bottom left
screenshot) – Selecting this option (from Window menu at the top of the
UI) will open the Maya Preferences window; from here, select the “Time
Slider” category from the left pane (see Fig. 1.1.1, middle screenshot).
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Arcs – Organic Movement/Natural Motion
• In the Preferences window, under the “Time Slider” section, set the animation
and playback range to 20 frames, which is just less than 1 second at 24 frames
per second (fps):
• Playback start/end = 1/20.
• Animation start/end = 1/20.
Note
The “Playback” and “Animation start/end” can also be set interactively from
the input fields underneath the “Time Slider” in Maya (see Fig. 1.1.1, right
screenshots). The gray box between the input fields can also be dragged
left and right to increase or decrease the playback range.
• In the Preferences window, under the “Playback” section, set the following:
• Playback Speed: = real time [24 fps].
Note
Setting playback to real time will force Maya to attempt to maintain a
constant playback rate of 24 fps. This setting is critical in evaluating the
animation in real time in the Viewport.
FIG 1.1.1 Animation preferences.
Maya Grid Display
For the ball bounce, we’ll be working on animating the ball bouncing across
the scene. While working, it is useful to have the Grid display in Maya setup
appropriately for the scene to preview the animation. As we’ll be animating
the ball traveling a fair distance across the ground plane, let us set up the grid,
so that it is larger and extends across more of the Viewport:
• From the top of the user interface, select the Display menu and select:
• Display > Grid [] Options.
Note
To select options within Maya from any of the menus, click the small square-
shaped icon at the right of the menu item (see Fig. 1.1.2, top left screenshot).
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• The “Grid Options” window will open (see Fig. 1.1.2, bottom left screenshot).
From here, the display of the Grid in the Viewport can be customized. Set
the following: Size > Length and width = 40.00 units (see Fig. 1.1.2, bottom
left screenshot).
• Hit “Apply and Close” at the bottom of the window to apply the change
and close the dialog window. The size of the Grid displayed in the scene
view will be larger (see Fig. 1.1.2, middle screenshot).
Note
The background color in the Maya Viewport can be toggled from the
default blue color to gray/black with the following shortcut key:
Alt + B = Viewport background color.
The Grid display can be toggled on/off from either of the following:
• The Viewport panel icons at the top of the panel window. Toggle on/off
the Grid icon (see Fig. 1.1.2, top right screenshot).
• The “Show” menu from the panel drop-down menus above the panel.
Toggle on/off “Grid” from here (see Fig. 1.1.2, bottom right screenshot).
FIG 1.1.2 The Maya grid options and
show toggle.
Creating the Bouncing Ball
We’ll use a primitive NURBS sphere for the bouncing ball animation.
• From the top row of menus at the top of the Maya User Interface, select
the “Create” menu and select:
• Create > NURBS Primitives > Sphere.
This will activate the create tool, click and drag near to the origin of the
scene (intersection of the grid) to create a new NURBS sphere (see Fig. 1.1.3, left
screenshot).
The Maya Channel Box
Maya’s Channel Box can be used to set the position of the ball and scaling:
• With the NURBS sphere still selected, toggle on display of the Maya
Channel Box with Ctrl + A shortcut toggle (see Fig. 1.1.3, second
screenshot from left).
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Arcs – Organic Movement/Natural Motion
FIG 1.1.3 The Maya Channel Box
and Smooth Shade Display.
Note
The Channel Box displays the following by default:
• Name of the selected object listed at top – “nurbsSphere1.”
• Transform channels – Translate/Rotate and Scale X/Y/Z.
The values shown here correlate with the position (Translate X/Y/Z), rotation
(Rotate X/Y/Z), and scaling (Scale X/Y/Z) of the object (or node) in the scene
view (or Viewport), and the values update automatically when the object is
transformed in the Viewport.
The Channel Box can be used to numerically position, rotate, or scale objects
in the scene:
• With the sphere selected, click with the left mouse button in the first
numeric input field in the Channel Box for “Translate X.” With the left
mouse button still pressed down, drag downward to the “Rotate Z”
numeric input field for the object and then release the left mouse button.
Note
The selected channel input fields will be highlighted in blue to show that
they are selected. The last selected input field (Rotate Z) will show the
number selected and highlighted.
• From the numeric keypad on your computer, hit 0 and Enter – this will set
all of the selected attributes in the Channel Box to value = 0 (see Fig. 1.1.3,
second screenshot from left). The sphere will be positioned at the global
origin (Translate X/Y/Z = 0.0).
At the bottom of the Channel Box is a heading titled “INPUTS”; this is the input
attributes for the sphere.
• Under INPUTS, click on “makeNurbSphere1” to display the input attributes
and double-click in the “Radius” section and type 2.4 to set the Sphere’s
radius to 2.4 units (see Fig. 1.1.3, second screenshot from left).
• Shading in the viewport panel can be toggled between Wireframe and
Shaded display from either the shading toggle buttons at the top of
the panel, the Shading menu at the top of the panel, or shortcut keys 4
(wireframe) or 5 (shaded) (see Fig 1.1.3, right screens).
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Animation Preferences – Key Tangents
For the animation of the bouncing ball, we start by blocking out the motion
in this initial phase. Keyframes for animation in Maya can have different
interpolation types, and these types will create different motion between
the keyframes on playback. “Stepped” interpolation between keyframes
will create a blocking jump in motion on playback, which is useful when
validating the overall timing.
The default interpolation type that Maya uses when setting new keyrfames
can be set from the Animation Preferences window:
• From the top of the Maya User Interface, select the following to open the
Preferences window: Window > Settings/Preferences > Preferences.
• From the Preferences window, select the following category from the left
pane: Categories > Settings > Animation (see Fig. 1.1.4).
• On the main part of the window, scroll down to the “Tangents” section and
set the following from the drop-down menus:
• Default in tangent = Linear.
• Default out tangent = Stepped.
FIG 1.1.4 Animation preferences –
key tangents.
Linear Tangency creates straight line motion between the keyframes. The
object will move at constant velocity when using Linear Tangency. “Stepped
Tangency” will create a jump between the motions at the keyframes, as the
motion is flat and then jumps to the next value. Do not worry about the
technicalities too much right now; the key interpolation can be viewed later
in Maya’s Graph Editor, which we’ll cover later (see Fig. 1.1.12).
• Scene file with the Ball model setup is included with the project files as
1.1_00_BallBounce_00_Ball.ma.
Note
The preferences as set here will apply to all keys set while working on
the scene and any other scenes. Remember to set this option back to
“Clamped” when working on the refining stage of the animation.
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Selection and Transformation Tools and Settings
While animating, you should be aware of the different transform tools and
options.
Maya’s Toolbox on the left of the interface includes the buttons to select
whether you are in selection or transform mode in the scene. When
interacting with your scenes to animate, you will mainly be either selecting
the objects or transforming them to animate (Transform = Move/Rotate/
Scale). The icons are fairly self-explanatory and each mode can also be
accessed from shortcut keys (see Fig. 1.1.5, left screenshot).
Tool Settings
The different modes for the selection and transform tools can be set from the
Tool Settings window (see Fig. 1.1.5, middle screenshot). Double-click any of the
tools in the Toolbox to open the Tool Settings. From here, you can set whether
you will be moving, rotating, or scaling objects in the scene in Local or World
modes. Generally, these options should be set as the default, although there
may be instances where you want to, for example, to move objects in Local or
Gimbal modes instead of the default World modes. The transform Gizmo icon
will update in the scene view depending on which mode is selected.
Transform Marking Menu
Tool Settings for the transform tools can also be accessed quickly from the
Maya Marking menu in the Viewport by downing the following:
• With the mouse cursor over the Viewport, press and hold the shortcut key
(i.e., Q = Select or W = Move).
• With the shortcut key depressed, click and hold the left mouse button to
display the marking menu (see Fig. 1.1.5, right screenshot).
• From the marking menu, select the option required (see Fig. 1.1.5, right FIG 1.1.5 The Maya Toolbox and Tool
screenshot – “Local” mode enabled). Settings window.
Animating the Ball Bounce
To animate the ball, we’ll use Maya’s standard transform tools to position and
keyframe the ball at different positions during the animation:
First, set the Panel display to display Single Pane as Side Orthographic View:
• Make sure that the Maya Panel Layout is set to Single Pane view from the
Panel menu (at the top of the Panel): Panels > Layouts > Single Pane.
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Note
You can use the shortcut toggle of pressing the Spacebar on the Keyboard
quickly to toggle between the default Four Panes layout and Single Pane
layout.
The Single Pane that is maximized is the pane the mouse cursor is over when
hitting Spacebar quickly.
• In the Single Pane view, press and hold the Spacebar on the Keyboard.
This displays the default Maya Marking menu. Click the left mouse button
on the “Maya” box in the center and drag the mouse cursor to the right to
select and highlight “Side View” option (see Fig. 1.1.6, top left screenshot).
Note
The different orthographic views for the pane can also be set from the
Panels menu: Panels > Orthographic > Side at the top of the pane (see
Fig. 1.1.6, bottom left screenshot).
In the Side View, select the Sphere and hit “F” shortcut key to frame the
Sphere.
Note
The F shortcut frames selected objects in the current view, whereas
A shortcut frames all the objects in the view. The Shift + A and Shift + F
shortcut keys will frame in all active panes.
• With the sphere selected, enable the Move Tool (W shortcut).
Note
The Move Tool will display in the Viewport as an arrow icon. The three
arrows represent the different transform axes. Green arrow represents
Y-axis, blue represents Z-axis, and red arrow represents X-axis. Selecting
either axis handle will change the display to yellow.
• Select the Y-axis (pointing up) to enable Y-axis translation; the axis handle
will change to yellow (see Fig. 1.1.6, second screenshot from left).
• Drag the Y-axis move handle upward, so that the sphere is positioned
with base at the origin (the thick black line at Y = 0) (see Fig. 1.1.6, third
screenshot from left).
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