Automatic Envelope

The Skin->Automatic Envelope command in the Actor module allows you to select a default circle or curve and automatically extrude it the length of a skeleton chain, thereby creating a default envelope for the chain.

An automatic envelope has the following behaviour:

• It can only be assigned to a single chain, not objects grouped as a skeleton.
• It is assigned as a local envelope; so it is the child of the first joint of the chain to which it is assigned. Envelope vertices are never assigned to the chain root.

Initially, vertices are not assigned to the chain effector either, but you can assign them to it manually later using the Skin->Reassign Manually command.

• It is deformed by the skeleton, like a flexible envelope.
• It uses the same Envelope Initial Assignment dialogue box as other types of envelopes; that is, its vertices can be assigned 100% to a joint (Full Weight) or relative to the n nearest joints (Weighted). The default is 2.

For an overview of envelopes, their use and classification, refer to Skin for Skeletons in the Modelling User's Guide.

Procedure

1. Select a chain that has no envelope.
2. Choose the Skin->Automatic Envelope command.
3. Click the left or middle mouse button to pick a curve or a default circle for the automatic envelope:

• Left mouse button allows you to pick a curve for the automatic envelope. The curve must be drawn in the xy plane.
• Middle mouse button selects a default circle for the envelope.

4. The Automatic Envelope dialogue box is displayed.
5. Set the parameters of the envelope and click Ok.

Parameters

Type of Envelope

If you select a default circle to generate the envelope, you can choose whether the result is a patch or a NURBS.

When you draw and pick a curve, the envelope is the same type as the picked curve and you cannot modify its type; in this case, this option is ghosted.

Capping

You can cap the top or bottom of the envelope, or both.

• Bottom (Start): The envelope is capped or uncapped, at the start of the chain.
• Top (End): The envelope is capped or uncapped at the effector.

Steps per Joint

Defines the resolution of the envelope.

Envelopes Initial Assignment

Once you click Ok in the Automatic Envelope dialogue box, the Envelopes Initial Assignment dialogue box is displayed.

1. Select the weighting assignment and the assignment depth according to which the envelope is assigned.
2. Click Ok to apply the settings or Cancel to exit the dialogue box.
3. An envelope the length of the chain is generated along the chain's local axis, but can be scaled later.
4. The envelope is assigned to the chain.

 

Parameters

Assignment Method

• Full Weight (old method): The envelope's vertices (in the case of flexible envelopes) or centres (for rigid envelopes) are weighted 100% relative to the closest joint.
• Weighted: The envelope's vertices or centres are weighted relative to the n closest joints. The default is 2.

Default nb of Joints Assigned

If you select the Full Weight option, this text box is not available.

If you select the Weighted option, you can specify the number of joints (or skeleton objects) to which each vertex in the envelope is initially assigned, with the percentage weighting based on relative proximity. The default value is 2.

Note:

This distribution applies to vertices not already governed by bounding models.

For example, if you specify 3, then all vertices not governed by a bounding model are assigned to the three nearest joints or objects, and weighted according to the relative proximity of each. For a description of bounding models and their influence, see the Creating a Bounding Area for Envelope Vertices section of the Modelling User's Guide. For details of related menu cells, see the Bounding Model section of this guide.

Assignment Depth

• No Maximum: Includes all hierarchies.
• Maximal level: By default, shows the number of levels in the currently selected hierarchy. You can change this value. If you set it to 0, then select Ok, the operation is cancelled.

Last updated 02-apr-1998