Maya Python: Apply Transformation Matrix

I have been looking for thi answer but i don't seem to figure it out anywhere, so i hope i could get my answer here...

I'm in Maya Python API and i want to apply a transformation Matrix to a mesh.

This is how i made the mesh:

    mesh = om.MFnMesh()
    ShapeMesh = cmds.group(em=True)
    parentOwner = get_mobject( ShapeMesh )
    meshMObj = mesh.create(NumVerts, len(FaceCount), VertArray, FaceCount, FaceArray ,parentOwner)
    cmds.sets( ShapeMesh, e=True,forceElement='initialShadingGroup')
    defaultUVSetName = ''
    defaultUVSetName = mesh.currentUVSetName(-1)
    mesh.setUVs ( UArray, VArray, defaultUVSetName )
    mesh.assignUVs ( FaceCount,  FaceArray, defaultUVSetName )

This is how i create the TFM:

m = struct.unpack("<16f",f.read(64))
mm = om.MMatrix()
om.MScriptUtil.createMatrixFromList(m,mm)
mt = om.MTransformationMatrix(mm)

Basically i read 16 floats and convert them into a Transformation Matrix, however i don't know how to apply the mt matrix to my mesh...

I managed to get the Position,Rotation and Scale from this though, maybe it helps, this way:

    translate = mt.translation(om.MSpace.kWorld)
    rotate = mt.rotation().asEulerRotation()
    scaleUtil = om.MScriptUtil()
    scaleUtil.createFromList([0,0,0],3)
    scaleVec = scaleUtil.asDoublePtr()
    mt.getScale(scaleVec,om.MSpace.kWorld)
    scale = [om.MScriptUtil.getDoubleArrayItem(scaleVec,i) for i in range(0,3)]

Now my last step comes in applying this Matrix to the mesh, but i can't find a good way to do it, does someone know how to do this on maya?

Thanks in advance: Seyren.

Solution

Not sure what you mean by applying the matrix to your mesh, but if you want to update the position of each point by transforming them with that matrix, then here you go for a given MFnMesh mesh and a given MMatrix matrix:

import banana.maya
banana.maya.patch()
from maya import OpenMaya

mesh = OpenMaya.MFnMesh.bnn_get('pCubeShape1')
matrix = OpenMaya.MMatrix()

points = OpenMaya.MPointArray()
mesh.getPoints(points)
for i in range(points.length()):
    points.set(points[i] * matrix, i)

mesh.setPoints(points)

If you don't want to directly update the points of the mesh, then you need to apply the matrix to the transformation node by retrieving its parent transform and using the MFnTransform::set() method.

Note that I've used in my code snippet a set of extensions that I've wrote and that might be helpful if you're using the Maya Python API. The code is available on GitHub and it also comes with a documentation to give you an idea.