In FontLab, you can only have beginning and ending masters on any particular axis. You can extrapolate, but that's difficult to control. If you want more than two masters along an axis, you need something like Superpolator.

Although, there is sort of a workaround for FontLab. If you add a second axis, you can go from, say, light to regular along one axis and from bold to regular in the other. In order for this to work, you need to duplicate the "regular" master in both axes, which means you will "waste" a master and also have to make sure to repeat any changes you make in the duplicated master. It really gets to be impractical if you want to add, say, a width axis on top of this. Superpolator is much more flexible for working with interpolation.

What are best practices for building out multiple masters in both directions like this?

Use Superpolator. Using an arbitrary number of masters is pretty convenient.

Superpolator looks amazing but seems pretty complex… is it easier to use than it looks?… creating Multiple Masters in FontLab is pretty basic… what is the best Workflow for using it, any tips I can pick up on before giving it a try?

Looks like I'll be ordering Prepolator, Superpolator and Font Remix Tools 1.6 really soon. Cool stuff…

Superpolator looks amazing but seems pretty complex… is it easier to use than it looks?

Superpolator is incredibly easy. To Fontlab's credit their Multiple Master interface is also very simple. But it has some irritating bugs that can impact your workflow and the nature of multiple master technology limits one's ability to do some cool multi-axis extrapolations that Superpolator does really well.

Workflow with Superpolator is based on .ufo, which is an xml-based exchange format for font development. You get the fonts in and out of FontLab using Python scripts (which are included with RoboFab tools and/or Prepolator).

If you have both FontLab and Superpolator running at the same time, when you update the .ufo from FontLab, it automatically is reflected in Superpolator. (This is also true of Prepolator.) You can also update, from within FontLab, glyphs that have been changed in the .ufo or import .ufo's generated by Superpolator or whatever.

The only major problem is that reading and writing fonts to .ufo can be a bit slow, especially when you need to do a whole font with hundreds of glyphs, since it's done with interpreted Python within FontLab.

My understanding is that the new version of FontLab (coming soon, I hope) will natively support .ufo, which should make working with external .ufo-based tools much smoother.

The only major problem is that reading and writing fonts to .ufo can be a bit slow, especially when you need to do a whole font with hundreds of glyphs, since it's done with interpreted Python within FontLab.

FWIW, Tal Leming’s UFO Central app (included with Prepolator) handles the job faster than the Robofab or Superpolator scripts.

Nice… thanks for the additional info.

Anyone use Type Supply's MetricsMachine? I have my workflow down so well with Metrics/Classes/Kerning that I'd almost not bother introducing anything else.

MetricsMachine is very good. I find it makes me more thorough and systematic than when I do kerning in FontLab. If you do use it, it's pretty much an all or nothing deal. You can't very easily do some of your kerning in FontLab and some in MetricsMachine.

From MetricsMachine, you can export either to a feature file or an afm file. In the latter case, the kerning is expanded to simple pairs, rather than classes, and the number of pairs can be quite large. If you export a feature file (which makes more sense usually), you just copy and paste this into the OT editor in FontLab. There's no kern table and you completely bypass FontLab's class definition system, etc. There is also no need to worry about "key" glyphs (which are a FontLab thing, not an OT thing). Once you have the kern feature in FontLab, the only way you can see the kerning in FontLab is in the OpenType Features Preview panel.

It's a very powerful app designed to do one thing really well--manual kerning. Some features I haven't even tried yet (like "transformations").

superpolater looks amazing but it only runs on mac :^( hehehe

Thanks Mark et al. for the answers.