Menu Cells

Skin -> Envelope Assignment

When you initially assign an envelope to a skeleton, each vertex or centre is assigned to the nearest joint(s) or objects, with automatically distributed weights.

You can subsequently fine-tune the initial assignment to selected skeleton joints or objects using the commands in the Skin -> Envelope Assignment menu cell commands in the Actor module.

Some editing operations require an automatic reassignment to apply the changes. For details, see Reassign Automatically.

Colour coding indicates its assignment, as described in Show Vertices. This colour coding of vertices' assignment makes reassignment easier.

For an overview or creating and editing skeleton and skins, see the Skeletons section and see the Skin for Skeletons section of the Modelling User's Guide.

For more ways of changing the deformation of envelopes, see also the Skin -> Deformation Parameters and Skin -> Deformation Curves menu cell commands.

How Flexible Envelopes are Mapped

When assigned to skeleton chains, flexible envelopes map their vertices to the nearest skeleton joint(s).

When assigned to skeleton objects, flexible envelopes map their vertices to the centre of the nearest skeleton object(s). Consequently, it is not important what kind of object you use as a skeleton object, since its geometry is not considered.

How Rigid Envelopes are Mapped

Rigid envelopes map the centre of the envelope object to the nearest joint(s) or skeleton model(s). As a result, some operations are not applicable to rigid envelopes, such as Skin -> Show Vertices and Reassign Manually.

For rigid envelopes, be aware that the envelope root is never assigned to a joint.

Show Vertices

The Skin -> Show Vertices command allows you to view the assignment of vertices in flexible envelopes; each vertex is highlighted in a colour matching the joint to which it is assigned.

Note:

The vertex has the same colour as the joint if the weighting is greater than 50%. If a vertex is not assigned to any single joint more than 50%, or is not assigned to any joint, it remains white.

1. Select an envelope.

2. Choose the Skin -> Show Vertices command.

3. The vertices' assignments are displayed.

Colour Skeleton

The Skin -> Colour Skeleton command colours skeleton joints or objects using the default colours green, cyan, yellow, and magenta.

As well, if you assign any kind of flexible envelope (automatic, local, global) to the skeleton, it applies the same colours to the associated vertices.

Tip:

If, instead of loading a whole scene, you choose Get -> Element to load an actor (skeleton plus envelope), the actor's colours are lost. In this case, the Colour Skeleton command is especially useful.

1. Select a chain root.

2. Choose the Skin -> Colour Skeleton command.

3. Follow the mouse button instructions as described below:

Left mouse button colours the entire chain and its descendants in the default colours.
Middle mouse button resets the colour to white.
Right mouse button exits the mode.

Colour Joint

The Skin -> Colour Joint command allows you to change the colour of skeleton joints or objects and the associated envelope vertices.

1. Select a joint.

2. Choose the Skin -> Colour Joint command.

3. Left or middle-click to toggle through the object colour palette (blue, red, green, cyan, yellow, magenta).

4. Right-click to end colour selection.

Bounding Model

Once you have created a skeleton, you can select a joint or object in the hierarchy and create a bounding model around your selection.

As the name suggests, a bounding model describes the area of influence around the joint, either by limiting the assignment of envelope vertices, or forcing certain vertices to be assigned to a specific skeleton model. Bounding models are only useful for skeletons with envelopes, but can be created before assigning the envelope and edited as required.

Bounding models are retained even if the envelope is cut from the skeleton and another is assigned.

Bounding models are displayed only when Show -> Controls is activated. As the "children" of the associated joints, they use the same display colour.

You can scale, rotate, and/or translate them as desired.

Notes

Bounding models are applied only during initial assignment and automatic reassignment.

If you create/edit a bounding model after you have already assigned an envelope, you must choose Skin -> Reassign Automatically to implement the associated changes in assignment.

Procedure

1. Draw one or more chains and/or models. Place them in a hierarchy as desired.

2. Define this as a skeleton. You can either:

Choose Skeleton -> Group as Skeleton and click the left mouse button to Set Skeleton.
or
Assign an envelope to the hierarchy.

In either case, the hierarchy is now defined as a skeleton.

3. If you want to verify vertices' assignment, choose either Skin -> Modify Weights to view weighting values in the Envelope Weights dialogue box.

4. If you want to create a bounding model to control vertices' assignment, select a skeleton element and choose Skin -> Inclusive/Inclusive Limit/Exclusive.

5. Select the shape of the bounding model using the mouse buttons.

Left mouse button creates a bounding box.

Middle mouse button creates a bounding cylinder.

Right mouse button creates a bounding sphere.
6. You can then scale, rotate, and translate the bounding model.

Note:
You can also edit the geometry of a bounding box.

7. If you assigned an envelope before creating or editing the bounding model, choose Skin -> Reassign Automatically to implement the changes in assignment.

Types
Bounding models can be combined for more realistic deformation. For example, to achieve a progressively diminishing influence of the joint, you could use both an Inclusive bounding and an Inclusive Limit box. For details on how this works, see Combining Bounding Models of the Modelling User's Guide.

Inclusive Limit
This type of bounding model defines the joint's zone of influence, similar to a clipping operation. When using Inclusive Limit:

Any vertex falling outside its boundary cannot be assigned to the joint.

Skeleton elements outside the bounding model can still affect the vertices inside the bounding model.

Inclusive
Any vertex falling within the bounding model is assigned 100% to the associated skeleton element, without regard to relative proximity to the skeleton element.
Points falling outside any inclusive bounding model are assigned and weighted (according to their relative proximity) to the n closest joints; n is defined in Default nb of joints assigned in the Envelope Initial Assignment dialogue box. The default is 2.

Exclusive
Any vertex falling within the bounding model is prevented from being assigned to the associated joint.

Shapes
All types of bounding model come in the same three shapes: a box, a cylinder or a sphere. Only the box shapes can be edited. You can tag and transform their points to define a more accurate area over the envelope.

Modify Weights
After assigning an envelope to a skeleton using the initial assignment parameters, you may still need to fine-tune the way the envelope responds to skeleton movement or create specific deformation effects.
The Skin -> Modify Weights command displays the Envelope Weights dialogue box in which you can reassign/reweight vertices to joints or skeleton objects, or assign them to the effector (which is not part of the initial envelope assignment).
This command works on tagged vertices only (for envelope models with geometry). For rigid envelopes, no vertices information is available: you simply reassign or reweight selected envelope elements (such as a meta-clay element) to skeleton joints or objects.

Tip:
It is often easier to use the Bounding Model or Reassign Manually commands to reassign envelope vertices than to use this dialogue box.

Procedure
1. Select one or more envelopes and tag the vertices you want to modify.

You can select more than one envelope and edit them one at a time in the Envelope Weights dialogue box without closing it.

If you selected a rigid envelope, tagging is not required.
2. Choose the Skin -> Modify Weights command.
3. The Envelope Weights dialogue box is displayed. The dialogue box is interactive with the time line so that you can change the frame number while keeping this dialogue box open.
4. In the Selected Envelopes scroll box, select an envelope.
5. Information on tagged vertices and their assignment is displayed in the Tagged Vertices and the Joints/Weights scroll boxes. The Weight slider value registers 0 until you actually highlight an element from the list.
6. Select one or more of the vertices in the Tagged Vertices scroll box and view their assignment and weighting in the Joints/Weight scroll box.

If you select one vertex, your selection is highlighted on the envelope in the window.

To select multiple vertices, press Shift and make your selection.

For a rigid envelope, no vertex information is available. You use only the Weight slider and the Joints/Weight scroll box.

The same weight value is assigned to vertices selected in the scroll box or tagged vertices, unless you select the Weighted option.
7. You can now edit the weighting of the selected vertices or all the vertices in the list, relative to a skeleton element.

Choose either Selected Vertices or All Vertices.

In the Joints/Weights scroll box, select a joint, object, or effector. The value of the Weight slider is updated to reflect your selection.
8. Apply the new weighting in absolute terms or additive terms.

Absolute sets the weight to an absolute value.

Add adds or subtracts a specific value to the current weight.

Add Percent adds or subtracts a percentage of the current weight.

If you select Add or Add Percent, you can select the Weighted option.
9. If you select the Weighted option, it automatically interpolates the weight values across the whole area of the selected vertices - there is a progressively diminishing effect spread out over the vertices associated with the selected element. Otherwise, the same weight values are assigned to all selected vertices.
10. Set the Weight value using the slider. If your selection makes the combined weighting exceed 100, the weight values for all elements are recalculated.
11. To view the results of the modifications, select either the Auto Refresh option or the Refresh button.
12. Click Ok to accept the new weights and assignments or Cancel to exit the dialogue box and undo any modifications.

Envelope Weights Dialogue Box

Restrictions and Tips
It is often easier to use the Bounding Model or Reassign Manually commands to reassign envelope vertices than to use this dialogue box.
The Modify Weights command ignores bounding models for joints. This is also true of the Reassign Manually command.
The interaction of selections in this dialogue box is somewhat complex and should be understood before use. It is useful primarily when you wish to:

View information on vertices' weighting

Assign specific weight values to a few vertices, in which case it is easier than drawing bounding models.

When you select vertices to edit, they are not always highlighted in the window.

Selection Parameters

Selected Envelopes
A scroll box displays the names of all envelopes selected in the window. Any envelopes without tagged vertices are not included in the list. Highlight an envelope to display information on tagged vertices and their assignment.
You can highlight more than one envelope at a time. However, the Joints/Weights scroll box can only display one skeleton at a time, so this is not a common approach.
If you do this, the Tagged Vertices scroll box shows a list of vertices corresponding to those which are tagged on the first envelope in the scroll list. A "d" beside each means that the displayed value is not necessarily the same for all selected envelopes.
In a few specific cases, it may be useful for you to highlight multiple envelopes in the scroll box, such as if you have skinned identical curves to create symmetrical envelopes around a skeleton. In this case, you can highlight multiple envelopes and then edit the weights of one or more symmetrical tagged vertices in a single operation.

Tagged Vertices
Lists any tagged vertices for a selected envelope by their identification numbers. When modifying the weight of an envelope, you must tag some vertices. When modifying the weight of a rigid envelope, no vertices are listed.

Modified for:

Selected vertices: Modifies the weight assignment for any vertices you have highlighted in the Tagged Vertices scroll box.

All vertices: All vertices in the Tagged Vertices scroll box are assigned the value for the Weight slider. If you choose this, you do not have to highlight any vertices in the list.

Interaction among Selections
When you highlight an envelope in the Selected Envelopes scroll box, the tagged vertices are listed by number in the Tagged Vertices scroll box. You can edit the weights for selected vertices in the scroll box or all of them in a single operation.
Examples:

If you highlight one or more vertices and choose Selected vertices, this modifies the weighting only for the highlighted vertices. If you do not highlight a vertex but choose Selected vertices, a message appears prompting you to select a vertex.

If you choose All vertices, all vertices in the scroll box are assigned to the same elements and weighted according to the same weighting choices (unless you selected the Weighted option, in which case there is some interpolation of the weight).

For Rigid Envelopes
For a rigid envelope, no vertex information is available. In this case, select the entire envelope and weight it relative to selected elements, interacting only with the Weight slider and the Joints/Weights scroll box.

Weighting Parameters

Weight
For a flexible envelope, this option sets the weight value for all or selected tagged vertices relative to the assigned skeleton element.
For a rigid envelope, this option sets the weight of the selected envelope (range 0 to 100%).

Weighting (Menu)
Selects the weighting formula. Use the Weight slider with any of these options to change the values.

Absolute sets an absolute value for all tagged vertices or selected ones, depending on your choice. This is the default formula.

Add adds or subtracts a value relative to the current value. For example, you can enter -20 to subtract 20 points from the current weights of all tagged vertices or selected ones.

Add Percent adds or subtracts a percentage relative to the current value. For example, you can enter -20 to subtract 20 percent from the current weights of all tagged vertices or selected ones.

Weighted (Option)
If selected, this option automatically interpolates the weight values across the whole area of the selected vertices - there is a progressively diminishing effect spread out over the vertices associated with the selected item in the Joint/Weight scroll box. The result is a smoother interpolation between points. This option can only be selected if you have selected Add or Add Percent weighting.
Your adjustments apply specifically to the selected element without considering or affecting assignment to others. However, vertices' weighting must be between 0 and 100%, regardless of how many elements they are assigned to. If your adjustments cause the weighting of a vertex to go below 0 or above 100, there is an automatic readjustment of weighting over all the assigned elements to respect this restriction.

Interaction among Weighting Selections
There is an interaction between the Weight menu, the Weight slider, the Weighted option, and the Joints/Weights scroll box.
In most cases, the Weight slider affects the weighting of only the selected element in the Joints/Weights scroll box. However, the total weighting for the selected vertices cannot exceed 100; in this case, the weight values for all elements are recalculated to bring the total to 100 or 100%.
The Weighted option can only be selected in conjunction with the additive weighting modes: Add or Add Percent.
For example, if you select Add Percent from the menu, select the Weighted option, and enter 50 with the slider, this is the result:

The vertex closest to the selected element gets 50% more assigned weight in reference to that element.

This assignment effect diminishes gradually across selected vertices assigned to the element until the most distant points have 0% more weight added to them.

Joints/Weights
Lists each joint or object in the skeleton, and the effector, if any, and displays the weight values for the associated vertices. Initially, vertices are assigned to one or more elements for a total of 100%. When you edit the weighting value for one element, it does not recalculate the weight for other elements unless the combined weight for all elements exceeds 100%.

Auto Refresh
Automatically updates the scene with the modifications you make. If you like, you can deselect this option and use the Refresh button only when you want to see the changes you have made.

Refresh
Allows you to view the results of your modifications immediately.

Reassign Manually
The Skin -> Reassign Manually command allows you to reassign tagged vertices to another joint or skeleton object, or assign them to the effector (which is not part of the initial envelope assignment).
Reassign Manually is applicable only to flexible envelopes. For rigid envelopes, you can reset their assignment. The easiest way to do this is by using the Skin -> Modify Weights command to modify weighting values of tagged points.
The Reassign Manually command ignores bounding models. This is also true of the Modify Weights command.
Whenever vertices are assigned to parts of skeletons (whether automatically or manually), the assignment is always based on the initial, undeformed position. Before reassigning points manually, it helps to reset the actor, to visualize the starting point before you start reassigning. To do this, choose Skeleton -> Reset Actor.

Procedure
1. Select the envelope and show its vertices using Skin -> Show Vertices.
2. Tag the vertices you want to reassign.
3. Choose the Skin -> Reassign Manually command.
4. Pick the new joint for the tagged vertices using the left mouse button. Middle-click to unassign the tagged vertices. The vertices are reassigned or unassigned.

Reassign Automatically
The Skin -> Reassign Automatically command automatically resets the assignment and weighting to the initial (undeformed) assignment. It can be used for flexible and rigid envelopes.

Note:
Some editing operations need an automatic reassignment to apply the changes. For example, if you assign a global envelope to a skeleton hierarchy and then insert a new element into the hierarchy (a chain, object, or bounding model), the new element is not recognized by the global envelope until you choose Skin -> Reassign Automatically or Reassign Manually.

Procedure
1. Select an envelope.
2. Choose the Skin -> Reassign Automatically command.

A message warns you that automatic assignment will destroy the current assignment. This means that any manual reassignment or weight modifications will be lost because all vertices will be reassigned to the nearest element, regardless of their current weight values. The reassignment will nevertheless take into account any bounding models.

The Envelopes Initial Assignment dialogue box appears, in which you can again choose the weighting method (Full Weight or Weighted) by which to reassign the envelope.
3. Once you fill in the Envelopes Initial Assignment dialogue box, all vertices are reassigned to the nearest skeleton element(s).

SOFTIMAGE 3D Reference - 19 APR 1996