Using CAT in 3ds Max - Part 1 - Preset Rigs
The Character Animation Toolkit (CAT) is a character-animation plug-in for 3ds Max. It facilitates character rigging, nonlinear animation, animation layering, motion-capture import, and more. In this introductory "Using CAT in 3ds Max" tutorial, we will walk you through the basic CAT workflows. From creating and editing preset rigs, fitting them to a given mesh, and generating a walk cycle to test your work, you'll be a CAT pro in no time.
- Recorded in: 3ds Max 2011
- This tutorial is intended for use with 3ds Max version 2011 or higher.
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CAT is an animation system that operates within 3ds Max, much like Biped
(formerly known as Character Studio).
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The CAT skeletal animation system makes it very easy to rig your
characters, and then animate them using a friendly layer-based
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To use CAT, you first need to create a CAT rig.
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This is an easy process that starts in the Helpers panel.
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Choose CAT Objects from the pull-down menu
and then click the CATParent button.
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From there you can select a rig from a list of Presets, and then create
the rig with a simple click and drag, much like you would do with a biped.
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The list of presets is extensive as you can see
and even includes a familiar looking biped.
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What makes CAT significantly attractive is the fact that you can
easily create rigs for multi-legged creatures.
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These include quadrupeds such as horses or panthers,
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or you can go the extra mile and create quick rigs for crabs,
spiders or even centipedes.
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Some other special rigs use geometry instead of bones,
to mimic the final appearance of a character.
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In most situations, you will be starting from one of the presets
and edit it to fit the model you are trying to animate.
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In some particular cases, it is possible to start a rig "from scratch"
and build it up to fit a special design.
You will take a look at that scenario later.
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In the scene you downloaded for this tutorial, consider this humanoid
character you want to animate.
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Given its human aspect, you will rig this mesh by using
a Base Human rig preset.
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First though, it is good practice to view the mesh in XRay mode,
by selecting the mesh and pressing Alt+X on the keyboard.
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It is also advisable to freeze the mesh before creating a skeleton for it.
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This makes it easier to adjust the skeleton without accidentally
selecting or moving the geometry.
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You can now create a CATParent rig from the Helpers menu.
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Choose the Base Human preset and click and drag from between
the humanoid's legs upward to create a rig.
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Once the rig is created, there are two places where you can manipulate it:
The Modify Panel and the Motion Panel.
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The Motion panel is used for animation and you usually go there
only after you have adjusted the rig properly to fit the mesh.
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Adjusting the rig is done in the Modify panel. Here you can adjust
individual limbs to your liking by moving, rotating or scaling them.
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If you are familiar with Biped, this is a bit like working in Figure mode.
You are in fact adjusting the "figure" of the skeleton.
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First thing you want to do is adjust the overall height of the skeleton.
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This is best done early on as you won't be able to adjust it later,
after you start animating the rig for example.
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In the Modify panel, you can adjust the overall height by editing
the CATUnits Ratio.
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Always use the Hips as reference and not the top of the head.
Not all bipedal creatures are created equal.
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In this case, a CATUnits Ratio of about 0.67~0.68 should work fine.
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Notice also the name of the Cat Rig. At this point it reads "Base Human".
Change it to Humanoid_.
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This has an effect on all the bones in the skeleton,
which now all have a Humanoid_ prefix.
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The underscore is optional and is used here to separate the prefix
from the rest of the limb name.
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Notice also that the whole rig is driven by this triangular node
that you just renamed.
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This is the topmost parent in the hierarchy, and in this case should be
relocated to 0,0,0 to match the position of the mesh.
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From this point on, you are ready to edit the skeleton.
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Start with the hips. Viewed from the side, use the Move tool
to position the Pelvis hub inside the mesh.
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You may even need to rotate the pelvis a bit so that it flows naturally
with the mesh pose.
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You can also edit the parameters of individual bones. In this case,
a pelvis height value of about 15 seems to fit the hips area better.
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With the pelvis in place, you next tackle the character's left leg.
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Start with the foot platform. This is an IK target that drives
the IK solution for the leg.
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Move it and rotate it to match the position of the character's foot.
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Select the rig's foot itself (Humanoid_LFoot). Notice that you can edit
that as well, and that the rotation of this skeleton part
is at the ball of the foot.
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In the Modify panel, notice also that you can add a number of digits
for the toes.
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If the character is barefoot, you would probably provide him with 5 digits
for 5 toes. If he has shoes on, then one digit is sufficient.
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You can then adjust the parameters of that digit.
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Set the number of Bones to 1 as you don't need the extra toe joints.
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Select the thigh and adjust its position slightly.
You might even rotate it a bit for a more natural pose.
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If the knee seems offset from the side, then select it
and adjust its position.
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You can see how flexible this type of adjustment is,
so keep on working on that leg until you are happy with the adjustments.
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Once you are done, make sure that a bone on that leg is selected
and then click the Copy Limb Settings icon.
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Select any limb on the opposite leg and click
the Paste/Mirror Limb Settings icon to copy your work to the other leg.
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Move up to the spine. Some work is needed here
because of the humanoid's initial pose and proportions.
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Using the Rotate tool, work the Spine bones from bottom to top
to follow the curve of the humanoid's back.
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Ultimately, select the Ribcage bone and move it into its correct
location. This will automatically scale the spine bones in the process.
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To help with the skinning later on, you can opt to adjust the parameters
of the spine bones, and of the rib cage.
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Similarly, adjust the head into place and edit the neck bones parameters.
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Next you adjust the arms.
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Start with the character's left arm. Select the collarbone
and adjust it in place.
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Next adjust the upper arm's position at the shoulder level,
and then rotate it locally into place.
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Adjust the rotations and parameters of the lower arm and hand,
and also move the hand into position.
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This character has a thumb but no fingers
as if he's wearing some sort of glove.
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With the hand selected, set the number of digits to 2. One will be for
the thumb, and the other representing the gloved four fingers.
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As you select these extra limbs, you notice they are made of three bones
(representing the knuckles).
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You can choose a different number in different circumstances
but three bones in this case work well.
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Use Move and Rotate and adjust the parameters of these bones
to follow the geometry of hand and fingers.
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Once you're done, and as you did earlier with the legs, select a limb
on the left arm, copy the pose, and then mirror/paste it to the other side.
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That's it! This is how you adjust a CAT rig to fit a skeleton.
You are now ready to skin the mesh and animate the rig.
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Skinning is a complex process in itself and usually requires
a fair amount of fine-tuning.
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However, for the purpose of this tutorial, you will just apply basic
skinning and accept the default setup which probably wouldn't be ideal.
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Unfreeze the model, select it and press Alt+X to cancel XRay mode.
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With the model selected, apply a Skin Modifier.
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Choose Add Bones and in the Dialog that appears,
make sure the Display mode is set to Display Children.
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Apart from the triangular node and the two foot targets,
all the bones are hierarchically linked to the pelvis.
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Select the Humanoid_Pelvis entry and press Ctrl+C to select all
the children bones.
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Click Select to Continue. The bones are added to the Skin modifier.
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To test your work, you will set a basic walk cycle to the character.
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Select a CAT rig element, usually the base triangular node
but any bone would do.
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Go to the Motion Panel. The red icon seen here is what specifies
whether you are in Setup mode (what you have been doing so far)
or in Animation mode.
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At this time, you cannot even go into Animation mode because
there are no active animation layers.
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These will be discussed more in detail later but for the time being,
click the layer pull-down menu and choose the last option.
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This creates a CATMotion layer with a default walk cycle animation.
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Click the Setup/Animation toggle button to enable Animation mode.
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Play the Animation to see the results.
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As mentioned a moment ago, there may still be adjustments to be made
at the Skin level, but don't worry about these right now.
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Later, you will learn how to adjust the walk cycle to be more befitting
a particular character.
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There is just too much sway and swivel here that just doesn't go
with this particular humanoid.
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In this movie, you learned how to create a preset rig
and adjust it to match a particular mesh.
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In the next movie, you learn how to create a rig from scratch,
for those characters or creatures that are slightly out of the ordinary.