OK a few days ago I wrote in about a process that I was using to get an exact deformation using a combination of skeletal animation and blend shapes. The blend shapes were created by rotating a joint and then modeling the deformation fix I wanted and then rotating the joint back to its bind pose. I then created a set driven key so the rotation of a joint would control the blend shape. The problem I was having was this, the joint rotation was making it difficult to model the deformation I was going after because it was causing a vertex translation to swap on the Y and Z axis. Ragtag helped me out by telling me that if I moved the tweak node to the top of the input stack I could move the vertices like normal. Well I did that and it works great. I also had an animator I work with tell me about a set up that uses the tweak node and set driven keys. You use the joint rotation to drive the envelope of the tweak node. This set up is real sweet because all you have to do is set up the set driven key stuff and then rotate your joint and model your deformation and your done. Now this is a great set up but I have found that it only works once per surface. This is a problem because I'm using a single surface polygon model. I tried going into the hypergraph and selecting the tweak node and duplicating the node using the duplicate upstream graph option and the duplicate input connections option as well. Neither of these options are producing the effect that I'm going for, which would be the addition of tweak nodes for deformation fixed on new joints. Here is the big question: Is there a way to add additional tweak nodes to a model that can be used in conjunction with set driven keys to fix deformations on any joint in your model? Here is what I found in the Maya help section on tweak nodes..... I don't see anything on adding tweak nodes. If this isn't possible then it will be rather disappointing because this is a feature that I was referring to in an earlier post of min of a feature that Max has that Maya doesn't, vertex or CV accurate level deformations.
Point tweaking is moving or setting keys on the individual points of an object. When you tweak the points of an object for which you have already created some deformers, Maya automatically prevents the unexpected effects that can occur when you use deformers. Maya does so by applying the tweaks to the object before applying any deformations to the object.
When you create deformers, Maya creates tweak nodes as well as deformation nodes. In the dependency graph, Maya places the tweak nodes upstream from the deformation nodes so that any point tweaking is carried out before the evaluation of the deformation nodes. This placement means that, by default, an object's deformation order includes point tweaking first, and then includes deformations in the order that the deformers were created.
Avoid changing the number of points after you create deformers
You can do point tweaking on objects after you have created deformers for them, but you should avoid changing the number of the object's points (for example, CVs, vertices, or lattice points). Changing the number of points can lead to unexpected deformation effects.
Note that when the deformation order includes point tweaking first (the default), CVs may not move in the same direction as the Move tool's manipulator if the attributes of the deformers do not have their initial (reset) values. If you would like to change this, reset the deformers to have their initial (reset) values. Alternatively, you could change the deformation order so that Maya applies the point tweaking after applying deformations. However, if Maya applies point tweaking after applying deformations, you may get unexpected effects when you use the deformers.
If you do some point tweaking and then want to check how the object deforms without the tweaking, you can disable the tweak node.
To change point tweaking's deformation order:
1
In the scene, move the pointer to the object being deformed and press the right mouse button.
A marking menu is displayed.
2
From the marking menu, select Inputs > Complete List.
The List of history operations window is displayed for the selected object.
3
Move the pointer over the name of the tweak node (default name: tweakn) whose order you want to change. Press the middle mouse button, drag over the name of the operation that is where you want point tweaking to take place, and release the mouse button.
To disable a tweak node:
1
Open the tweak node's Attribute Editor.
2
In the Attribute Editor, open Node Behavior.
3
Set Node State to HasNoEffect.
To enable a tweak node:
1
Open the tweak node's Attribute Editor.
2
In the Attribute Editor, open Node Behavior.
3
Set Node State to Normal.
Hope someone can help!
Nick Zuccarello
SOE Character Artist