Paint Blend Shape Weights Tool via Python/MEL?

[jmalaska]

Trying to do some very targeted blendshape painting. What I'd like to be able to do is select a series of vertices with soft selection, and have that selection be my "painted weights". I don't really want to have to go through manually painting weights.

Are there Python commands to help with this?

I can't dig to find out what the Paint Blendshape Weights tool is doing. The Node Graph doesn't show any intermediary that would hold this data.

https://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2020/ENU/Maya-Cha...

[lee.dunham · Accepted solution]

So its certainly possible, although it will depend on how comfortable you are with python.

First off, you need to get the components and "weighting" from the soft selection;

https://github.com/ldunham1/maya_utilities/blob/master/ld_soft_cluster.py

def _get_soft_selection():
    """
    Return the current soft selection components and normalised influence weights.
    :return: List of components and matching weights.
    :rtype: list(str), list(float)
    """
    # Grab the soft selection
    selection = om.MSelectionList()
    soft_sel = om.MRichSelection()
    om.MGlobal.getRichSelection(soft_sel)
    soft_sel.getSelection(selection)
    dag_path = om.MDagPath()
    component = om.MObject()

    # Filter Defeats the purpose of the else statement
    iter_sel = om.MItSelectionList(selection, om.MFn.kMeshVertComponent)
    elements, weights = [], []
    while not iter_sel.isDone():
        iter_sel.getDagPath(dag_path, component)

        # Grab the parent of the shape node
        dag_path.pop()
        node = dag_path.fullPathName()
        fn_comp = om.MFnSingleIndexedComponent(component)
        vtx_str = node + '.vtx[{}]'

        for i in range(fn_comp.elementCount()):
            elements.append(vtx_str.format(fn_comp.element(i)))
            weights.append(fn_comp.weight(i).influence() if fn_comp.hasWeights() else 1.0)

        iter_sel.next()

    return elements, weights

Then, modify the blendshape weights using the component index and soft selection weight - these two posts should help you out there.

https://yantor3d.wordpress.com/2017/09/16/inside-the-node-blendshape/ 

https://soup-dev.websitetoolbox.com/post/setting-blendshape-weights-through-maya-api-7116714?pid=128...

Hint: You're modify this to affect the blendshape base weights, although you can also access target specific weights too;

blendshape.inputTarget[0].baseWeights

Hope this helps!

[jmalaska]

Lee, this is wicked awesome. Thank you for dropping your knowledge! Exactly what I was looking for. Cheers!

[lee.dunham]

Not a problem, glad it's helpful 🙂