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Simple Walk
Tutorial |
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Part 3 - Animation
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This is the third and final
part of a tutorial on designing a simple character, making a
walk cycle for it, and then animating it walking in a scene.
The three parts are:
1)
Building the body parts,
2)
Making the character's
skeleton, and
3) Animating the character.
In this part you will first
make a single cycle of a walk and the use it to make a
longer walk sequence an animated scene. Since the main
reason for this tutorial is to animate a character, the
objects are rather simplistic. You will need the project
that you built in part two, or you can use
this Anim8or project instead. |
|
What's a Walk Cycle? |
| Before you
animate your character, you need to know about Walk Cycles.
This section gives a very simple introduction to Walk Cycles
for those who are unfamiliar with them. More advanced
animators can skip to the next section. It would also be
useful for beginners to find a good animation book and read
the chapters on walking. |
| A cycle
is a sequence of animation that can be repeated over and
over again so that a short animation can be used to fill a
long time in an animation. In addition to the normal
movement, for a cycle to work, the position and motion of an
object must flow naturally from the final image to the first
as well. Repetitive motion, like a character walking, does
this quite easily. So, to animate a character walking across
a room, you only have to animate one full step for each foot
and then repeat it enough times to get you character to the
other side. |
| In the case of
a walk, it's even simpler. Since both legs move the same,
just out of sync by 50%, you only have to animate one half
of the cycle, then copy the animation to the other half.
A 6 minute animation of the
making of the walk cycle is
available via the following table.
| |
From school server
(fast but only works at school) |
From internet server (slower but
works anywhere that has ADSL) |
| part 3a |
SWF file |
web page |
Web page |
|
| |
Here you'll use
5 key positions to make a walk cycle. By spacing them a few
frames apart, Anim8or will fill in the missing poses and
make a longer animation with smooth, fluid motion. The 5
poses for the first half of the walk cycle are shown below:
 |
Open the Sequence Editor
with the Mode>Sequence menu command. The Sequence
Editor will create a new, blank sequence if there aren't any
in the current project. If there already is one, use the
Sequence>New command to create a new one. Open the
sequence properties dialog with Settings>Sequence.
Name the sequence something like Walk Cycle, then click on
the 
and select your character from the dialog that appears. Set
the length of the sequence to 40. Close the dialog and your
figure should appear in the frame. |
 |
| A time line
should be visible just below the work area. If not, select
the Options>Track Window command from the menu. Each
space represents one frame, and the dark gray one is the
current frame. You can click on any frame to see your
character's pose at that time. |
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The Animate Key |
There are two
ways you can make changes to the position, angle, size, or
some other aspect of a figure or object. One is to change it
for all time, such as the way that you build a model. The
other is to apply the change only for a certain time period
so that it changes from frame to frame when you play a
scene, and thus becomes animated.
You use the key frame 
to select which kind of change you to make in the Sequence
and Scene editors. When it's off changes you make are for
all time, and when it's enabled 
changes are animated. Any value you change is recorded for
the current frame. Then when you play the scene your values
are updated each frame to match the ones you set for that
frame.
You don't have to set keys
in each frame, just those in the defining frames. Missing
values are smoothly filled in for you. The values you set
are called key values, and frames they're in are
called key frames. |
Enable animation ,
hide body 
parts, and show axis  .
Start in the front view and select the left thigh
(the right one on the screen). Make sure that you are on
frame 0 in the Track Window. Change to the side view.
Set rotate joints 
from the toolbar, then click on the tip of the thigh bone
and rotate it out to the left about 35 degrees. You can see
the angle in the markings on the green arc. Each tick is 30
degrees, so rotate the thigh a bit past the first tick. A
small black square will appear in the time track indicating
that there is a key position for some joint in that frame.
Since animation is enabled changes that you make are only
for frame 0.
When you have it right, hold
down the Ctrl and Shift keys (to temporarily switch into
Select mode) and click on the left shin. Alternately you can
select multiple bones while in Select mode and work with
them by rotating any one of the selected bones. This way you
won't accidentally change the position of unselected bones.
Bend the knee back just under 45 degrees, making that
position a key one as well. Finally, select the left foot,
bend it slightly to make it level with the ground.
Each joint that you touch
will add a key for the current frame. If you accidentally
move the wrong one, either use the Undo command, or select
the key in the track window and delete it with a Cut or
Delete command. |
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| Now comes a bit
of work. Move to each of the next 3 poses. Advance the frame
number by 4 each time, and position your skeleton to match.
Then make 5 more key poses after that, this time with the
left and right legs in the other's position. When you're
done you'll have a complete walk cycle. Click the play
button and watch it go! |
|
Making a Scene |
A 6 minute animation of the making of the walk cycle is
available via the following table.
| |
From school server
(fast but only works at school) |
From internet server (slower but
works anywhere that has ADSL) |
| part 3b |
coming... |
coming... |
coming... |
Now you're
ready to do some animation. Switch to the Scene Editor with
the Mode>Scene command and start in the front view.
Make the length of the scene 80 frames with
Settings>Scene. |
| Now add your
character to the scene. Use Build>Add Figure and
select your character's name from the dialog and it will
appear in the center of the scene in its default pose. This
actually adds a reference to your character, not the
character itself. You can have as many references as you
like. If you go back to the Figure Editor and change
something in your character, all references will
automatically be updated as well. |
| Now make sure
that you are in frame 0 and a copy of your sequence. First
select your character, then Build>Add Sequence from
the menu. Your character should change into the first key
pose in your sequence. |
Select your character and
move it up so that it is standing on the ground. If you
click the play button 
your character should do one walk cycle, and then freeze in
the final pose for the rest of the Scene. The keys positions
are not linked circularly like they used to be in earlier
releases of Anim8or. |
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| Now go to frame
40 by clicking on the right place on the track bar. Or you
can move forwards and backwards a frame at a time with the
Right- and Left-Arrow keys. Add the same sequence again with
Build>Add Sequence. Now when you play the scene your
character will do two complete walk cycles. |
Set the frame
to zero and select your character. Drag to the left about
2/3 to the edge. Enable animation with the key animation
tool  .
Now any change that you make to an element's position, size,
etc. will animate that property. It will create a new key
for the current frame if one doesn't already exist. Now go
to frame 80, being careful not to deselect anything. Move
your character to near the right of the frame. A new
position key is added at frame 80, and since frame 0 doesn't
already have a key one is added there as well to mark your
figure's position at the start. A white line appears showing
the location of the path. |
 |
When you move
an object, there are two things that can happen:
1) If the animate tool is
selected ,
then the position is only changed at the current frame,
and adjacent frames up to the neighboring position keys.
This is how you normally animate something.
2) If the animate too
isn't selected  ,
then the position is changed for the entire scene. If
there aren't any position keys the object is simply
moved. If there are then all of the keys are moved by
the same position, so the entire path moves.
|
Now double
click on your character and in the Orientation section
select Relative to: Path. Now it will face the direction
that the path is going. Change to the Camera viewpoint, and
use World 
coordinates. Go to frame 40 or so, select your character,
and make sure animation is enabled. Then click down with the
left mouse button and drag up and to the right. Your
character will move away from you and stay in the plane of
the ground. Hit the play key and watch it walk along the now
curved path, passing in front of the camera and out of view. |
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| Go back to the
front view and select the camera. Select Build>Face
Target from the menu. Then click on your character, and
the camera will always face it. Go back to the Camera View
and play your scene. Now the camera follows your character
so it doesn't leave the field of view!
Does it go by too fast to
see? Then select the View>Preferences command and in
the bottom Frame Rate section check the Limit Playback box.
Now your scene will play at a more constant rate. The
default value is 24 frames per second, the same rate used
for film
projection in movie theaters.
You can change this to another rate if you want. |
|
Make a Movie |
| Now make an .AVI
movie. Make sure you're in Camera View, and select
Render>Render To File. Select AVI and All Frames, and
enter a name for the file. Click OK and a Video Compression
dialog appears. This will vary depending upon the software
installed on your computer, but you can select one of
several different compression schemes for the output. Full
(Uncompressed) makes VERY big files, so it's best to choose
another one. The best overall codec is called Divx. It is
not normally installed but you can find it on the web at
www.divx.com. The Indeo codecs by Ligos or Intel are
good, as is Cinepak by Radius is a good choice. Set the
options you want, and click OK to make a movie! |
| Future
Work |
| You may notice several
problems with the way your character walks. its feet may
appear to slide along the ground as it walks. It may float
above the ground, or its feet may go below the surface part
of the time. You can certainly reduce these problems by
carefully adjusting various positions, and you should give
it a try.
You will quickly find out
that this is a very tedious way to fix things. What you need
is a way to have Anim8or do these things for you. Future
releases of Anim8or will address these problems, with ways
to have the motion matched to the speed that a character
walks, and the height matched to the level of the ground,
without having to tweak each position by hand. So, hang in
there! |
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next to the title "Walk Cycle" in the track. This expands
the track to show individual bones. You can resize the track
window by dragging the resize bar 
up or down. You can select individual bones by clicking on
their row in the track. You should see six little black
boxes in the first (zero-th) column for the six bones that
have key positions set. 
next to the title to shrink the track back to a single line.
Carefully click on the 4th slot (counting from 0) to select
frame 4 of your sequence. A number "4" should appear in the
status bar at the bottom of the window. Then select the left
thigh and rotate it so that it matches the second image in
the sequence above. Since the animate tool is still green
these will become keys for frame 4. Then position the rest
of the joints as well. Now your second key pose is complete.
This pose is called a "crossover" position and is important
to get right, especially when animating at lower frame
rates, since it give valuable visual cues to the viewer that
the legs are changing order.
