Adding to envelopes

[ggg]

This is part of the NL/procedural power and the raison d' etre of new apps like XSI and Houdini
(They didn't show this at that school? :hmm: )

In XSI manual>Animation>Envelopes>Modifying Enveloped Objects


Modifying Enveloped Objects
Sometimes, after carefully assigning weights manually, you discover that you need to make a substantial change to the enveloped object, such as adding points. Luckily, you do not need to redo all your weighting — you can add and move points after enveloping using various techniques.

There are also some issues related to transforming envelopes (rather than the deformers), but it is still possible to scale an envelope if necessary.

Adding and Moving Points After Enveloping
If you add points to an object after enveloping it, those points are not included in the envelope operator. Similarly if you move points on an envelope, the MoveComponent operators are applied after the envelope deformation and may not give you the desired results. You can solve these problems by disabling the top of the stack while you make your changes.

To add and move points after enveloping
In an explorer, right-click the object’s Envelope Operator node and choose Disable from Here. The Envelope Operator and everything above it no longer affect the object. They now appear dimmed with strike-through text.
Make any changes required, such as adding and moving points.
Right-click the Envelope Operator again and choose Enable from Here. The Envelope Operator is reactivated, but the new points are not weighted to any deformers yet.
Assign weights to the new points using any method.
For example, you can get a quick rough weighting by selecting them, choosing Envelope > Reassign Locally from the Animate toolbar, and picking the deformers you want. After that, you can use painting or numerical editing to refine the weights further.

Moving Points in Relative Mode
When you move a point on an envelope, the result may not be correct if you later move the deformers. This is because the MovePoint operator stores data as an offset from the object center, and does not take into account the envelope deformation.

To solve this problem, make sure that Modify > Component > Relative Mode is on before moving points on an envelope. For more information, see Relative Mode in Chapter 4 of the Modeling & Deformations guide.

Alternatively, you can use Disable from Here in the operator stack as described in the previous section.

Transforming Envelopes
Envelopes behave differently from other objects when you transform them:

If you try to scale, rotate, or translate an envelope, it appears to be unaffected. This is because all of its points are assigned to the stationary deformers.
If Centers are visible in a 3D view, you can see that the envelope is “really” being transformed.

If you transform an envelope in Center mode, it appears to react in the opposite way. This is because transforming a center actually applies a compensation to the object’s points.
In general, it is not recommended to transform an envelope because you may get strange results if you later reset the reference pose. Instead, you can put the envelope and deformers in the same hierarchy or model and then transform the whole tree.

Scaling Envelopes
If your envelope is too big or too small, you can fix it by making it a child of the chain root, and then branch-selecting and scaling the chain root.

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