Aligning the Biped to the Model

Autodesk 3ds Max Tutorials > Character Animation Tutorials > Adjusting the Biped to the Model >

In this lesson, you'll pose a biped to fit a specific character by moving, rotating, and scaling biped parts.

When correctly posed, the biped's torso, arms, and legs fit just inside the mesh. Fingers and toes extend just beyond the mesh to make skinning easier later on.

When posing the biped, Figure mode must be turned on. This mode tells 3ds Max that you are posing the biped rather than animating it.

The character you’ll use in this lesson has a human form, and will not require a tail, ponytails, or props

Set up for this lesson:

Load the file align_wilson_start.max.
This scene contains a model of a man named Wilson.

The Wilson model
Inspect the model to see the number of fingers and toes. This model has three fingers and a thumb, and the fingers are short. Wilson is wearing shoes, so no toes are visible.

Prepare the model:

Your work with the biped will be much easier if you make a selection set for the model, make it see-through, and freeze it.

Select the entire model.
In the Named Selection Sets entry area on the Main toolbar, enter the name Wilson Mesh.
On the Display panel > Display Properties rollout, turn on See-Through.

The model turns gray and becomes see-through. Making the model see-through will allow you to see the biped as you pose it inside the model.
On the Display panel > Display Properties rollout, turn off Show Frozen in Gray.
This lets the model retain a little of its shading when frozen.
On the Display panel > Freeze rollout, click Freeze Selected.
You freeze the model so you won’t accidentally select it while working with the biped.

Create a biped:

Choose Create panel > Systems > Biped.
Click near Wilson’s feet in the Front viewport and drag upward to create a biped about the same size as the model.

Because Wilson is wearing shoes, there's no reason to have separate toes. You'll give the biped just one toe with one link, which will control the entire ball and toe of the shoe.
Near the bottom of the Create Biped rollout, change Toes to 1 and Toe Links to 1.
When you inspected the model earlier, you found that Wilson has three fingers and a thumb for a total of four fingers. The fingers are short, so only two finger links are needed.
Set Fingers to 4 and Finger Links to 2.
Wilson's neck is rather stubby, so he needs only one neck link.
Set Neck Links to 1.

Position the biped:

Open the Motion panel.
In the Biped rollout, click Figure mode to turn it on.
If the Biped rollout doesn’t appear on the Motion panel, select any part of the biped to make it appear.

ImportantBe sure to turn on Figure mode before continuing. Figure mode will retain the pose you are about to create.
Select the center of mass (COM), the blue tetrahedron at the center of the biped’s pelvis.
Tip You can quickly select the COM by clicking any of the selection buttons in the Track Selection rollout: Body Horizontal, Body Vertical, or Body Rotation.
In the Front viewport, move the COM to the center of the model’s hips.
Check in all viewports and move the COM as necessary to put it inside the character’s hips.

COM placed correctly in Left view

Pose the legs:

Select both the upper and lower parts of both legs.
In the Front viewport, scale both legs so the bottoms of the biped’s feet align with the model’s feet.
Select both thighs. Rotate the thighs to make the biped's legs parallel to the mesh legs.

The goal is to make the biped's legs go down the centers of the mesh legs, but you can't do it until you scale the pelvis.
Select the biped’s pelvis, the orange triangle around the COM.
Scale the pelvis on its local Z-axis so the biped legs go down the centers of the mesh legs.

You might need to rotate the legs again, and scale the pelvis again. Work back and forth between scaling the pelvis and rotating the legs until the legs go straight down the middle of the mesh legs.

Scale the legs:

In the Left viewport, right-click the viewport label and turn on Edged Faces so you can see the knee detail on the pant legs.
Scale and rotate the thighs so the knee joint falls at the center of the knee detail on the pants.

So far you have been posing both legs at the same time. It is possible to pose one leg or arm first, then copy and paste it to the other side.
In the Front viewport, select one calf. Scale the calf so the ankle joint falls just above the bottom of the pant leg.
Scale the foot so its bottom reaches the bottom of the mesh foot.
Select both the foot and calf you just scaled.
In the Copy/Paste rollout, turn on Posture. Click Copy Posture.
Click Paste Posture Opposite.

Now the two legs match.
In the Left viewport, check to see if the ankle joint meets the bottom of the leg. If not, change the Ankle Attach parameter on the Structure rollout to 0.2 or 0.25 to make the ankle match the leg.
In the Left viewport, rotate the thighs, calves and feet so they align as well as possible with the model.

The file align_wilson_legs.max contains the biped posed up to this point.

Position the arms and spine:

Select one of the biped’s upper arms.
In the Front viewport, rotate the upper arm upward to make the arm parallel with the model’s arm. Don’t be concerned with fitting the arm at this time; simply make it parallel.
Select all the spine links and make a selection set called Biped Spine.
In the Front viewport, scale the spine upward or downward to make the upper arm fall into place.
Select the posed upper arm. In the Copy/Paste rollout, copy and paste this pose to the other side of the biped using Copy Posture and Paste Posture Opposite.
Use the Biped Spine selection set to select the spine links. In the Left viewport, rotate the spine links slightly so they follow the curvature of the spine. You might need to move the lowest spine link to align the spine correctly.

ImportantDon't rotate the COM when posing the biped. Instead, move the lowest spine link to adjust the position of the spine and upper body.

Now that the spine is curved correctly, the arms might be out of place again.
Use the named selection set to select the entire spine. In the Front viewport, scale the spine again to make the arms fall into place.
Check the spine again in the Left viewport to ensure it still follows the shape of the character’s torso.
As with the legs and pelvis, you have to work back and forth between the spine and the arms to make both fall correctly inside the mesh.
In the Front and Left viewports, scale the widths of the spine bones to make them fit the mesh more closely.

Make each spine bone about two-thirds the size of the mesh. You will have to scale some spine bones more than others.

Pose the arms:

The posing of the arm starts with the clavicle bone, which connects the arm to the torso. Proper scaling of this bone leads to easier skinning of the underarm and shoulder areas later on.

Select one clavicle. In the Front viewport, scale the clavicle slightly along its X-axis so the biped's shoulder joint falls in the center of the mesh shoulder.

Left (blue) clavicle scaled slightly
In Top viewport, work with the upper and lower portions of the same arm. Scale and rotate the arm bones as necessary to fit it to the mesh, taking care to align the biped’s elbow and wrist joints with the same joints on the mesh.

Posed arm in Top viewport

TipYou can move quickly between parent and child bones by pressing Page Up and Page Down on the keyboard.
In the Front viewport, rotate the arm if necessary to make it go down the center of the mesh.
Select the clavicle, upper arm, and lower arm, and copy and paste the pose to the opposite side of the biped.
The file align_wilson_arms.max contains the biped posed up to this point.

Pose the hands:

Positioning the fingers is the most challenging part of posing the biped. Each finger joint must be moved and rotated separately.

You can rotate each finger and thumb joint, but you can move only the base of each finger and thumb.

You’ll have an easier time posing the fingers if you work with the bases of fingers first, moving each one into place before rotating and scaling the finger joints.

In Top, Front, and User viewports, zoom in on one of the hands.
In the Top viewport, rotate the hand slightly if necessary to make it fit the mesh better.
Scale the biped hand so the palm nearly reaches the point where the pinky finger starts.
Check the hand in the Left viewport, and if necessary, rotate it to fit the center of the mesh hand.
In the Top viewport, move the base of the thumb and each finger to match the base of the corresponding digit on the mesh. Don’t concern yourself with the rotation of the fingers just yet.
Rotate base of each finger and the thumb so each goes up the length of the corresponding mesh finger. You might find you have to move the base of the finger again to make it align correctly.
Scale the lengths of the finger joints so the first goes about halfway down the finger, and the last extends just beyond the mesh fingertip. This will help later on when skinning the character.
Using the Top and Front viewports, scale the width and height of each biped finger to about two-thirds the size of the corresponding mesh finger.
In the User view, rotate the finger joints to fit the fingers. You can also move each finger base up or down to improve the fit. Look at the hand from various angles to check the fit.

Tip To rotate the view around the hand, select one or more finger bones and use Arc Rotate Selected in the User viewport.

There is no shortcut to posing the hand correctly. You must look at the hand carefully from all angles to ensure the bones are centered down the mesh fingers and thumb. The thumb bones can be challenging to pose because they rotate differently from the fingers.
When the hand pose looks good, select all the hand bones, and copy and paste the posture to other hand.
Check the fit of the bones on the other hand. If necessary, scale or rotate the lower arm to make the fingers fit on the other side.
When a mesh is symmetrical, the hand bones should make an exact fit when pasted to the other side. However, meshes are not always perfectly symmetrical. In addition, if the center of mass is slightly off center, the hand will not fit exactly.

The file align_wilson_fingers.max contains the biped posed up to this point.

Pose the head and feet:

In the Left viewport, rotate and scale the neck link so the biped’s chin aligns with Wilson’s chin. Do not rotate the head.
In the Front viewport, scale the head to about half the width of Wilson’s head, and to its full height.
In the Top viewport, rotate the biped’s feet to match the angle of Wilson’s feet.
In the User and Left viewports, scale the foot and toe bones to represent the bulk of the shoe and the toe portion of the shoe. If you have difficulty selecting the toe bone, select the foot and press Page Down.

Complete the posing process:

As necessary, scale biped parts so they are about two-thirds the width of the mesh.
Wilson's pose is now complete.
Select the entire biped, and create a named selection set called Wilson Biped.
TipIt’s best to wait until you’ve finished posing the biped to make a biped selection set. If you change parameters on the Structure rollout and add more parts while you’re posing, any parts added in this way will not be part of a selection set made at the start of the posing process.
In the Biped rollout, click the expansion bar to display the Name field.
Enter Wilson Biped in the Name field.
All biped parts are now preceded by the words Wilson Biped. Naming the biped in this way greatly assists the process of merging characters into scenes with multiple bipeds.

TipGiving each of your bipeds a unique name is a good practice. For example, if you decide to merge the character into a scene that contains other bipeds, the merge process won't ask you about duplicate names, and you'll be able to tell them apart easily when selecting objects.

Save the pose:

Choose the named selection set Wilson Mesh, and click Yes on the warning dialog.
On the Display panel, turn off See-Through.
Save the scene to the file my_wilson_pose.max.
A finished version of the pose can be found in the file align_wilson_complete.max.

Applying the Physique Modifier