Previewing, Diagnosing, and Fixing Interpolation
Work from the visible result toward the underlying correspondence. First preview the designspace, then identify the failing glyph and its mismatched structure. Use automatic matching where it produces the intended result, and repair individual sections where it does not.
Previewing Interpolation Results
Open Window > Panels > Variations. In Map view, move the interpolation point through the displayed axes. In List view, use the per-axis sliders. Both control the dynamic instance: the location currently being calculated.
Variations List provides sliders and named master locations; this example has Weight and Width axes.
The Variations Map places masters and the preview location in a two-axis plane, making their spatial relationship visible.
The resulting #instance layer is a read-only generated preview, distinct from a drawn master. Edit the source masters to change its drawing. Make it visible in the Layers & Masters panel to compare its wireframe with a source drawing. Move slowly through the range and watch counters, joins, terminals, and attachment points as well as the overall silhouette.
Check endpoints, intermediate masters, and locations between them. In a multi-axis font, also inspect combined directions. A clean weight transition at normal width does not establish that the condensed weight transition is clean.
Scrubbing the space is a working compatibility test. An absent #instance is a visible symptom of unavailable interpolation, including incompatible masters; first check source participation and Preferences > Variations > Show #instance layer. In a single-master source, Variation within static family can supply additional open-font sources for comparison and interpolation.
The AAA participation control can exclude a font master from the blend. This changes the calculation; it is not the same as hiding that master's wireframe with the eye control. Restore the intended sources after an isolation test.
The floating Variations widget appears when the font has a variation axis. It shows one axis at a time, chosen from its title-bar dropdown, with the current glyph at several positions. Dragging its instance line is equivalent to moving that axis’s slider in the Variations panel. The panel's independent X/Y controls offer the anisotropic generation taught in Beyond the Uniform Blend; leave them at their normal settings when diagnosing an ordinary shared-location blend.
When a glyph has bracket breaks, the Variations widget marks the active range with a line in the selection color beneath its previews, including both endpoint masters. Other ranges are gray. Activate the range you want to inspect, then select one of its endpoint masters. The preview positions stay fixed as you change ranges. The Layers panel and Glyph window master selector check compatibility within that range; a different contour structure across the break is not itself an error. Bracket creation is taught in Bracket Layers, and point-trajectory editing in The Sigma Tool.
Link matching axes in the Variations panel keeps axes with matching tags linked when you change their locations. The setting is stored with the font and also applies to changes made through the Variations widget. Check it when moving one control changes another axis as well.
Diagnosing Incompatibility
Use the compatibility indicators in the Layers & Masters panel and on Glyph-window master buttons to locate suspect layers. The Font window's mismatch filtering can help collect affected glyphs. Open one and inspect its structure rather than repeatedly moving the preview slider without a hypothesis.
The Variations panel's Check masters geometry and Sort contours and start nodes controls affect automatic matching. Check masters geometry is an interpolation option, not a separate guaranteed report of every faulty glyph. Read the resulting status and inspect the glyphs it affects.
Read Matchmaker
Press 7 to activate Matchmaker. Its display connects corresponding nodes with master relation lines and identifies contour starts and indices. The visible-master selection controls which comparisons you see; keep the intended sources visible.
Matchmaker displays corresponding outlines and points from the masters together, making mismatches visible on the canvas.
The match status distinguishes three useful cases:
- Green: the displayed sources have a direct compatible structure.
- Yellow: compatibility depends on automatic matching corrections.
- Red: the available matching cannot produce a compatible result.
Green does not certify attractive interpolation. Look for relation lines that join different semantic parts, such as an outer contour and a counter, or travel around a contour from different starting positions.
With Show intermediates off, contour colors help compare ordering. With it on, the tool displays pairwise intermediate steps. Those steps are arranged for comparison between masters; they are not necessarily the actual named-instance locations in a multi-axis designspace.
Use the arrangement control to offset overlaid masters when coincident drawings obscure the relation lines. Match masters width supplies a display compensation for width differences; it does not redraw the masters.
A count or segment-type mismatch prevents direct structural pairing. A wrong contour order, direction, or start point can instead produce an incorrect blend despite matching counts. FontAudit's Kink in variation identifies another quality problem: a smooth source join develops a corner between masters. This test has no automatic fix: correct the geometry by hand, as discussed in Font Audit. Structural matching alone is not a remedy.
Making Masters Compatible
Save the source before applying repairs that can reorder or reconstruct contours. Start with one glyph so that you can inspect what changed.
Try automatic matching
The Variations panel’s Check masters geometry and Sort contours and start nodes options affect dynamic matching. The latter corrects contour order and start-node differences during interpolation, but cannot compensate for different on-curve node counts. To commit corrected ordering to the source, use Glyph > Match Masters, or Match Masters in Layers & Masters or the Matchmaker property bar. A normal click in Matchmaker respects the configured automatic-matching options. Shift-click requests the stronger set of corrections regardless of those current options.
Matching can sort elements and contours, relocate starting points, reconcile directions, and correct supported segment differences. It is more than a count comparison, but it cannot infer that an absent bowl or an extra decorative contour should be designed a particular way. Resolve genuine design-content differences yourself.
Inspect the masters after matching, including components and references. Do not assume that every source structure was retained unchanged just because the appearance stayed similar. Recheck the live instance and the intended reusable relationships.
Correct order, direction, and starts
If the wrong contours correspond, arrange them consistently in the Elements panel. If directions disagree, Alt-click a contour node in Matchmaker to reverse that contour. The Set PS contour direction control works on the current master; Shift-click extends that operation to the visible masters.
Shift-click a node in Matchmaker to make it the contour's start. Place starts at corresponding design landmarks. The Relocate startpoints control offers automatic placement; Shift extends it to the visible masters. Automatic bottom-left-oriented choices still need inspection when the masters' shapes differ substantially.
Reconcile a problem section
Use manual section matching only where the correspondence needs repair. It can add or remove nodes, so applying it indiscriminately to an already correct glyph can make matters worse. Before matching, review Allow to clean up segments: it permits removal as well as addition of nodes. Enable it only when that reconstruction is acceptable.
- Show the masters you intend to reconcile and identify the same continuous section in each.
- Drag a marquee around its beginning nodes across those masters. This establishes the blue beginning selection.
- Drag another marquee around its ending nodes to establish the orange ending selection. Extend a selection with Shift-drag where needed.
- Inspect both sets of boundaries, then press Enter to reconcile the intervening sections.
- Check the changed contours and repeat only for another unresolved section.
Inspect whether the reconstructed sections preserve the intended curves.
A repaired glyph should produce its live instance and pass the relevant structural checks. Finish by scrubbing the actual axes again. Check the drawing, spacing, and attachments at intermediate locations; a green status is a starting point for that design review, not its conclusion.