This tutorial will explain in a few easy steps how I mirror my Morphtargets. This is a method I recently stumbled upon while working in Maya, and I haven't seen any tutorials regarding how to do this in Max. So, without claiming to be the inventor of this method, I'm more merely translating between programs.
Anyhow, here we go:
First, get a head (Fig.01). Here's an old head I made during my studies. And we're going to make him smile!
First things first. The model has to be 100% symmetrical and with the pivot in the center for this to come out correctly (Fig.02).
Now let's make the needed targets. I strongly advise having a good system for naming things (such as L_eyebrow_UP) instead of trying to animate complex facial animations where the names of the morphtargets' names are all defaultXXX.
For this tutorial I'm only making four very quick targets (Fig.03).
Next is the fun part! Assign a Morpher to your main head and then assign your Morphtargets there (Fig.04).
Now, clone your main head, and rename it Right_Targets (Fig.05). Mirror your Right Targets as a Copy, and rename the mirrored head Mirror Targets (Fig.06) Tip: Since they occupy the same space, it's easier to select the two heads if they're put on different layers.