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HUMAN INDIRECT SKINNING WITH FREE-FORM DEFORMERS I
HUMAN INDIRECT SKINNING WITH FREE-FORM DEFORMERS I
sdb1987, added 2005-10-04 11:27:48 UTC 64,531 views  Rating:
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BUILDING THE SKELETON

As with figure drawing, the best advise anyone can give you is to study life. Study the things around you. Study true human, animal, and even plant anatomy.

1. Hide all surfaces but the single surface poly.

You�ll ultimately use the poly surface as your deformer. So you�ll use it as a visual reference for the placement of your skeleton�s joints. (You can also use the hiRez surface as a visual reference when/ if needed.)

In the Layer Editor�, highlight the Polys layer and make it Visible.

Turn every other layer Invisible.

2. Make the surfaces references.

This is just a time saving precaution�so you don�t accidentally select any of the surfaces while trying to work quickly and to keep unnecessary surfaces out of the way while still being able to see/ and use them as reference.

In the Layer Editor�, highlight the hiRez, the medRez, the loRez, and the Poly layers.

Hit the Reference button.

THE BACK

In the side view, make a series of joints imitating the back from the pelvis to the top of the skull.

1. Start with the ROOT in the side view.

Place and name the ROOT joint at the point where the pelvis and the spine meet.



Fig. Note 1.5 Place the ROOT joint and then place the lumbar1 joint just above it. You won�t be doing any spinal rotations using the ROOT, it�ll all start from the lumbar1 joint.

2. Place the spine joints up to the top of the head and to the forehead end.

(Use the following picture as a guide for correct joint placement.)

Follow the curve of the spine and placement of the head/ neck. Of course, your spine is made up of many more joints, but that would be rather tedious to animate�so this is a simplified version of the back. But if you want to be anatomically correct, place and label all the joints. This tutorial though, will only mention the joints placed here in this step.

click for larger version

In the front and perspective views, edit the placement of the spinal joints by translating or rotating each one individually. General rule: build the skeleton to the character model�don�t worry if things aren�t perfect. (I.e. the spine isn�t straight.) Note: also, don�t worry about the rotational axes yet. We�ll fix them later�.



3. Name the joints (as in the above picture).

lumbar1, lumbar2, lumbar3, thoracic1, thoracic2, thoracic3, thoracic4, cervical1, cervical2, skull, skullTop, and foreHead.

4. Create the jaw joints.

For an easier time when you edit the weights of the deforming skin�add a jawbone into the skull. In the side view�.

Create the mandible and mandibleEnd as in the picture below.



Fig. Note 1.6 Create the jaw for the character.


In the front and perspective views, edit the placement of the joints by translating or rotating the jaw joints to their correct places with in the character surface.

Connect the jaw to the skull/ back. Select mandible, SHIFT select skull, then Edit > parent (or hotkey p).



Fig. Note 1.7 Attach the new jaw to the skull. Select the mandible then SHIFT select the skull and parent.

5. In the front view, place the six optional rib joints.

This is another extra step. Though not necessary, this step helps visually for keyframe posing and in the binding and weighting process.



Name them: right_falseRib, left_falseRib, �trueRib1, �trueRib2. As in the picture above.

Translate them forward in space from side and perspective views.



In the side view, select the �trueRib2 (both of them) and Parent them to thoracic2.

Do the same for the �trueRib1 to thoracic1 and �falseRib to lumbar3.



LEGS

To IK or FK, that is the question�sorry, couldn�t resist! This is quite a huge debate in the setup community and I�m not going to get into it here. ;) What we�ll do with this character here is set up IK on the leg with a reverse foot setup. So far, this has proven quite effective for everything I�ve been doing. But if you don�t want IK on the leg, finish this section and skip the reverse foot section.

1. Build the left leg and name the joints.

In the side view, start with the hip to the knee, to ankle, to the ball of the foot to the toe.



Fig. Note 1.8 Put a slight bend in the knee, showing which direction the leg will bend. This way, when you add IK, the computer knows which way the knee is supposed to bend.

Name the joints: femur, knee, malleolus, metatarsal, and toe as in the picture above.

Modify > Prefix Hierarchy Names� and enter left_ in the name field.

2. Rotate the leg into position.

In the front view, translate the femur (along with the rest of the leg hierarchy of course!) to roughly the area where the ball of the left femur fits into the socket of the pelvis. Rotate the femur so the knee and the ankle line up with the model. Keep the leg itself straight, so don�t rotate the knee in this window!



Fig. Note 1.9 Translate the skeletal leg over and rotate the entire hierarchy so the ankle joint lines up with the surfaces� ankle area. So it ultimately resembles this picture. If needed, rotate the ankle joint so the ball and toe of the foot line up with the model also. �Again, don�t rotate the knee in this window!

3. Mirror the left leg to create the right one.

Instead of creating the right leg from scratch, use the Mirror Joint feature to duplicate part of the skeleton.

Select the femur and Skeleton > Mirror Joint options and set the YZ option. Hit the Apply button.



4. Do any manual edits if there are any needed on the new leg.

If your model isn�t symmetrical, you may have to manually edit the joints. So, as above, translate or rotate the joints as needed (still following the �rule� of the knee).

5. Name the right legs joints.

As with the left leg, name the right leg�s joints down the hierarchy: femur, knee, malleolus, metatarsal, and toe. Select the newly named femur, Modify > Prefix Hierarchy Names�, and enter right_ in the name field.

ATTACH THE LEGS TO THE BACK

The legs need to be attached to the spine. But you still want to have a separate pelvic rotation that doesn�t affect the back in any way. To do this, first you have to add another joint underneath the ROOT.

1. Create and name the pelvis joint.

This is the joint that will drive the pelvic rotations. As with the lumbar1 joint, the pelvis joint will be right next to the ROOT in space (but below it this time).

In the side view, create and name the pelvis joint just below the ROOT as in the picture. Edit the joint�s position in the front view if needed.



2. Attach the legs to the pelvis joint.

In the side view, select both legs (femur joints), SHIFT select the pelvis joint, and Edit > Parent.

3. Connect the pelvis to the ROOT joint.

Select the pelvis, SHIFT select the ROOT, and Edit > Parent.



Fig. Note 1.10 Close up of the spinal hierarchy near the ROOT. This setup ensures movement of the back and the pelvis independent of each other.

ARMS

Arms can be one of the most frustrating things to setup on a �human-type� character. From getting the right shoulder placement to getting the twist of the arm correct, there�s no perfect way of doing this part, so be prepared to rework this section a few times�just in case�. NOTE: This tutorial is based off of a character with palms facing forward. If your character has palms down you will have to modify the rotation editing you do to the chain.

1. Create a straight arm.

You want to start off with a straight arm so that the smaller �twist joints are in perfect alignment with the chain.

In the front view, create the left humerus. Hold down SHIFT and create the humerusTwist, elbow, radiusUlnaTwist, and wrist along a straight line. (Holding down SHIFT while creating the chain will draw the joints in a straight line depending on the first direction of the mouse.)



Fig. Note 1.11 Create the arm in a straight line. Notice the placement of the �twist joints. Both are relatively small.

Name the joints as labeled in the above step. Select the humerus, and use Modify > Prefix Hierarchy Names� and enter left_ in the text field.

2. Edit the locations of the joints by rotating and scaling.

When you line up your newly created arm with the mesh, you�re most likely to find that it doesn�t fit within the surface right away. It just needs some manual tweaking.

In the top view, translate the chain so that the humerus is roughly in the center of the area where the shoulder should be attached.

In the front view, rotate the humerus joint so that the skeleton chain lines up through the mesh�s wrist. Switch to the top view and rotate the humerus so that the chain runs through the mesh�s elbow area.

Scale both the humerus and humerusTwist joints in X (or down the chain) so that the elbow joint falls into the center of the mesh�s elbow area. (If you�re poly version of the model is too loRez, use the hiRez surface as a guide.)

Still in the top view, rotate the elbow joint so that the rest of the arm�s skeletal chain lines up with the mesh�s wrist area.

Scale both the elbow and radiusUlnaTwist joints in X (or down the chain) so that the wrist joint falls into the center of the mesh�s wrist area.



Fig. Note 1.12 Rotate the humerus joint so that the arm chain lines up in the center of the surface�s wrist area. Scale the each of the joints in X (down the chain) so they line up with their appropriate places in the mesh. Notice how the elbow joint doesn�t fall into the center of the mesh�that�s all right, it�s centered in the rotational direction.

3. Create the left hand.

The easiest way to create the hand is to start by making skeleton chains for each finger and ultimately parenting them to the wrist.

Draw the five-finger/ thumb chains in the front view as in the picture below.

click for larger version

Edit all the newly created joints locations by translating, rotating, and scaling the joints so that they are located in the center of their surrounding surface areas. If your character�s fingers aren�t straight, this task can take awhile and you�ll have to constantly jump between different viewing windows to make sure everything is aligned properly.



Fig. Note 1.13 If your character�s fingers weren�t created straight, aligning the joints with the surface could be tedious. Just take your time and switch between views often to line things up.

Name each of the chains down their hierarchy:

THUMB: thumbPalm, thumb1, thumb2, thumb3.

INDEX FINGER: index1, index2, index3, index4.

MIDDLE FINGER: middle1, middle2, middle3, middle4.

RING FINGER: ring1, ring2, ring3, ring4.

PINKY FINGER: pinkyPalm1, pinkyPalm2, pinky1, pinky2, pinky3, pinky4.

Place and name the palm joint.



Select the index1. SHIFT select the middle1, and ring1, then the palm joint and Edit > Parent.



Select the thumbPalm, the palm, and the pinkyPalm. Modify > Prefix Hierarchy Names� and enter left_ in the text field.

Parent the left_thumbPalm, left_palm, and left_pinkyPalm chains to the left_wrist.



Fig. Note 1.14 This is what the finished hand skeleton should look like.

4. Attach the arm to the torso.

Instead of attaching the shoulder joint directly to the spine, insert a clavicle joint for a more naturalistic shoulder control.

Place and name the left_clavicle as in images. Look at your own shoulder rotation, the clavicle bone is actually in front of the rib cage, so it�s driven from a point closer to the front. Translate the joint to this point.





In the front view, select the left_humerus joint, SHIFT select the left_clavicle, and Edit > Parent (or hotkey p).

Select the left_clavicle joint, SHIFT select the thoracic4 joint, and Edit > Parent (or hotkey p).



5. Mirror the arm.

Create a duplicate of the arm for a reference. When you mirror the arm, the local rotational axes aren�t pointing in the right directions. This is just one of the techniques you can use to create skeleton hierarchies and a way to edit them during creation.

Select the left_clavicle and Skeleton > Mirror Joint. The mirror options should still be set correctly from the previous leg mirror.



Fig. Note 1.15 After mirroring the clavicle, if your character isn�t symmetrical, you�ll have to edit the positions of all the joints in the chain.

6. Make duplicated arm a reference.

When you mirrored the left arm the local rotational axes didn�t mirror exactly the way you wanted them to. (You can check the axes by selecting the joint chain and Display > Object Components > Local Rotational Axis. It�s a toggle for display on and off.) The easiest way to fix this is to use this mirrored arm as a snap point reference for a new chain. This entire step is something that I�ve just found useful in speeding up the second arm�s local rotational axes editing�.

Select the newly mirrored clavicle (default name should be left_clavicle1.) Edit > Unparent to remove the arm from the hierarchy.



Edit all the joints so that they �line up� with their corresponding surface areas. Look to the left arm for references, etc. Also, you must take into account the �rules� of the other arm (i.e. do NOT edit the �twist joints.)



Fig. Note 1.16 If needed, edit the joints so that they �line up� with the surface.



In the Layer Editor, create a new layer, and name it Extras. Assign the mirrored arm to this layer and make it a Reference layer. As a reference, you won�t be able to select the arm, but you can use it as a point snap reference, unlike a template, where you just see it.

7. Create a new arm on top of the reference arm.

You�ll create a completely new arm chain right on top of the referenced arm. This way the local rotational axes will be created in the correct direction.

Skeleton > Joint Tool and turn on Snap to points.



Create the new arm chain starting from the left_clavicle1 and continuing until you have a new joint for every referenced joint.

You will have to use the arrow keys on the keyboard to step back up the hierarchy to create the hand. This way you don�t have to stop and start hierarchies and then parent. (I.e. draw a chain from the clavicle to the wrist and follow the hierarchy down the thumb. Then Arrow Key back up to the wrist and draw to the palm and index. Arrow Key Up to the palm and draw the middle�etc�etc�etc�.)

Name the arm chain just as you did for the left side�. Starting from the humerus, to the humerusTwist, to elbow, etc�.

Select the humerus and Modify > Prefix Hierarchy Names�. Enter right_ in the text field. Then with the right_humerus still selected, Display > Hide > Hide Selection or the default hotkeys: CRTL h.

8. Delete the reference arm.

Clean up the file by deleting the mirrored arm that you used as a reference.

In the Layer Editor, highlight the Extras layer and make the layer Standard.

Select the left_humerus1 reference arm chain and delete.

Show the hidden right arm by Display > Show > Show Last Hidden or default hotkeys: CRTL SHIFT h.

9. Attach the right arm to the skeleton.

To complete the skeleton, attach the right arm.

Select the right_humerus, SHIFT select the thoracic4, and Edit > Parent.

click for larger version

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