to be honest - i don't know where my fault was. Unhappily i didn't commit the not working version. In my plugin i
already used a virtual doc for some other calculations. thank you!
vd.ExecutePasses(c4d.threading.GeGetCurrentThread(), True, True, True, c4d.BUILDFLAGS_NONE)
md = c4d.modules.mograph.GeGetMoData(matrix)
for m in md.GetArray(c4d.MODATA_MATRIX): rdPoints.append(m.off)
works like a sharm.