Link Sub-Object

Select an object with the Physique modifier. > Modify panel > Sub-Object Link

Use parameters at the Link sub-object level to change how deformation around joints occurs. When a joint in the skeleton bends or rotates, Physique, by default, deforms vertices uniformly on either side of a joint. Change these defaults using the tools at the Link sub-object level. For example, adjust the amount of skin sliding that occurs along a limb as the limb bends, or change the angle of the crease between the upper arm and chest.

The Physique Deformation Spline

Like a 3DS MAX spline, the deformation spline created by Physique is a continuous curve through several points. While a 3DS MAX spline runs continuously from vertex to vertex, the deformation spline is a smooth curve running from joint to joint. The Bend, Bias, and Tension spinners change the shape of the curve, analogous to rotating or scaling the spline handles at a 3DS MAX spline vertex.

The deformation spline also takes into consideration twisting and scaling of the skeleton's links. At the Link sub-object level, you take control of the behavior of the deformation spline, and subsequently gain full control of the skin's behavior relative to the skeleton's movement.

Procedure

To adjust joint intersection parameters

  1. With Physique active on the Modify panel, click to turn on Sub-Object on the Modifier Stack rollout.

  2. Choose Link from the Selection Level dropdown.

  3. Click the link you want to work with.

  4. Select Active for the crease you want to manipulate; choose Crease at Parent's Joint or Crease at Link's Joint.

  5. Change parameters on the Physique Joint Intersections rollout.

    Assuming that you are working with the joint between the selected link and its child (the biceps link, for instance), select Crease At Link's Joint and change parameters. You then need to select the child link (the forearm) and activate its Crease At Parent's Joint. Adjustments to the Parent's Joint for this link will affect the other side of the same crease.

Interface

Link Settings rollout

Active: Activates the selected link when selected. Default=selected.

Turning off Active makes the link unavailable for vertex assignment, meaning that the link has no influence on any vertices. Any vertices within range of this link are not influenced by it and may be picked up by other nearby envelopes, or may be manually assigned without blending to any other link. Clearing Active makes Physique ignore that link as if it were never part of the skeleton.

Continuity: Maintains a smooth transition across the joint from the parent link to the current link. Default=selected.

When this box is selected, the effect of the link parameters passes smoothly across the joint to the connected link. When this is cleared, Bend, Twist, and Radial Scale are limited to the current link, which produces an abrupt transition across the joint. This is analogous to breaking the spline handles on a 3DS MAX spline.

Bulge Editor: Displays the Bulge Editor. The Bulge Editor represents bulge cross sections graphically.

Reinitialize Selected Links: Reinitializes the link and its vertex parameters based on the current link parameter settings. This does not change vertex assignments or manual reassignments.

For example, increasing the tension of a link can cause the spacing to change for the link's cross sections. Reinitializes Selected Links smoothes the spline, and makes cross section spacing even again.

Think of the skin being snugly stuck to the link. As the link parameters change, the vertices may bunch up or stretch out. Clicking Reinitialize lets the skin "slip" to it's original shape, establishing a new relationship to the deformation spline

Bend group

Bend tension affects the curvature of deformation spline through the joint. A low value, near 0, makes the spline linear and creates a sharp angle at the joint, like bending a hinge. High values, near 2, make the spline smooth through the joint, creating a rounded joint, like bending a firm hose. Bend bias pushes the effect along the spline toward one side of the joint or the other.

Tension: Sets the smoothness of a joint. A value of 0.0 produces a sharp joint. A value of 2.0 produces a rounded joint. Range=0.0 to 2.0; Default=0.5.

Bias: Displaces the pivot point about which vertices are bent. The default value of 0.5 centers the bend at the joint. Values lower than 0.5 move the pivot onto the child link. At 0.0, the bend effect is limited to the selected link.

Twist group

Twist parameters control the way the skin deforms when a joint rotates along its length, as in turning a doorknob.

Use Twist for Rigid: Turn on twist for rigid envelopes. Default=Off.

Turn off for the rigid envelope for a characters head, the head should not twist along the length of the link. You may want to turn this on for the forearm or upper-arm link if you're using rigid envelopes.

Tension: Values lower than 1.0 concentrate the effect closer to the joint. Values higher than 1.0 move the effect away from the joint. Range=0.0 to 2.0; Default=1.0

Bias: Shifts the distribution of the twist from one side of the joint to another. The default value of 0.5 twists the selected link and the child link equally. Values greater than 0.5 shift the twist to the child link. Default=0.5

Sliding group

Skin sliding parameters control the amount of skin sliding that occurs when a joint rotates. Range=0 to 1. Both Inside and Outside are set to 0.0, off by default.

Inside: As values increase, skin moves away from the joint. Default=0.0

Outside: As values increase, skin moves towards the joint. Default=0.0

FallOff: As values increase, the effect is localized to the joint. Default=0.5

Tip: Use sliding for knees and elbows.

Inside and Outside set to a value of 0 in the image on the left, and 0.25 in the image on the right.

Without skin sliding, vertices closest to the joint tend to compress on the inside and stretch apart on the outside, generally revealing the segments of the mesh. Outside sliding causes the vertices around the joint to move toward the joint, preventing localized stretching on the side that is greater than 180 degrees. Inside sliding causes the vertices to relax and slip away from the joint, preventing bunching of vertices on the side having an angle less than 180 degrees.

Radial Scale group

Radial Scale parameters expand or contract the skin by scaling the radial distance perpendicular to the link. They apply to any combination of user definable scale, bulge settings, or link length.

Tension: Values lower than 1.0 concentrate the effect closer to the joint as Tension approaches 0.0. Values greater than 1.0 move the effect away from the joint. Range=0 to 2; Default=1.0.

Bias: Shifts the effect of radial scaling. At the default value of 0.5, scaling affects both the selected link and the child link.

Values lower than 0.5 shift the scaling effect onto the selected link and values greater than 0.5 shift scaling onto the child link. At 0.0, expansion and contraction are limited to the selected link. At 1.0, expansion and contraction are limited to the child link. Default=0.5.

Link Scale: Scales the entire link radially, independent of the effect of any cross sections. At 1.0, the link is 'actual size' and this parameter has no effect. Other values increase or decrease the radial scale of the link. Range=0 to 10; Default=1.0.

CS Amplitude: Cross section amplitude has no effect unless the link has bulge angle cross sections. At 0.0, cross section deformation is turned off. Values greater than 1.0, up to the maximum of 10.0, exaggerate the effect of cross sections. Default=1.0.

Stretch: When selected, preserves the volume of the link's skin when the length of the link changes. The effect is similar to stretching or squeezing a material that is only partly elastic, such as a tough rubber hose. Default=cleared.

Stretch is turned on in the image on the left, and turned off in the image on the right. As the 3DS MAX bones change in length, the mesh expands and contracts when Stretch is selected.

Breathe: When selected, scaling a skeleton node changes the radial scale of the link's skin. When cleared, scaling a node has no effect on the scale of the skin. Default=cleared.

Linked 3DS MAX objects are shown in white. Notice that one of the objects is scaled larger than the others. In the left image, Breathe is selected, the mesh is scaled as the object is scaled. Breathe is cleared in the image on the right.

Note: The 3DS MAX objects linked together are used as the hierarchy for Physique.

Joint Intersections rollout

When a joint bends, the skin can "collide." Without collision detection, it can overlap unrealistically. This is especially likely when one or both of the links have bulges. Physique's joint intersection controls can detect skin collisions and correct overlap by creasing the skin.

By default, Physique draws a crease plane that bisects the joint and prevents vertices from each link from crossing the crease plane. The result can be a somewhat unnatural flattening of the bulges along the plane. Physique therefore provides controls that allow you to modify the effect of the crease plane.

Properly adjusted crease plane

You can modify the effect of the joint creases at both ends of the selected link. These joints are the parent's joint and the link's joint.

Crease at Parent's Joint group

The Blend From and Blend To points define the distance along the link that is affected by the crease plane. For the parent joint, the joint is at 0.0 and the crease plane has an effect from the joint to the Blend From point.

Active: Turns off the effects of the joint intersection controls. When this box is cleared, Physique makes no compensation for overlapping bulges.

Blend From: The area between Blend From and Blend To contains vertices that are partially affected by the crease plane. These vertices will be shifted, but not as much as those between the crease plane and the Blend From point. The distance of the vertices from the crease plane determines the exact amount of shifting. Vertices within the blend region that are closer to the intersection plane are shifted more than the vertices further away from it.

Blend To: Indicates the distance beyond which the crease plane has no effect.

Bias: Sets the strength of the crease plane effect within the blended region. A value of 0.0 means that the intersection plane will have no effect within the blended region; a value of 1.0 means that it will have a full effect within the blended region.

Crease at Link's Joint group

For the link's joint, the joint is at 1.0 and the crease plane has an effect from the joint to the Blend To point. Vertices that are at locations less than the Blend From point are not affected by the crease plane; vertices between the Blend From and Blend To points are partially affected by the intersection plane.

 

 

 


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