Hello Marcus, very interesting question.
I don’t think is possible to retrieve vertex data as direct matrices in jitter(please someone correct me if i am wrong!). There has been some discussion in how to access shader data: http://cycling74.com/forums/topic.php?id=26185
You need to bind the shader to an object. Look at the next example(attached):
if you apply the binding of the shader to the jit.gl.gridshape and then turn on the matrixoutput attribute, the jit.gl.mesh stills retrieves the original data from the gridshape. The shader wouldn’t work until you bind it to the mesh object.