Expressions as a Reusable System
Most expression work is written once, for one property, in one project — and then written again the next time, because there was never anywhere to put it. This section walks the jobs that changes.
What this section is
Six jobs you already do in After Effects, each one written twice: the vanilla After Effects path, and the same job in eXLib. Every entry has the same four parts.
- The task — what you're actually trying to accomplish, in three or four steps.
- How it goes in plain After Effects — the honest best-practice path, not a caricature.
- What changes with eXLib — the parts that move, and why.
- Step by step — the same job in both columns, one row per step.
The plain-After-Effects column is the real procedure, including the parts AE
does well. Where AE has a good answer — animation presets, EE to reveal expressions,
Copy Expression Only — the column says so.
The idea the six jobs share
An expression stops being a one-off when three things stop being manual:
- Its tunable values. A number buried in code is a number you have to find again. Turned into a variable, it becomes a control that gets created for you at apply time, on whichever layer you chose.
- Its layer references. An expression that reads three other layers is normally rewritten for every rig it lands in. Wired as variables, those references are asked for at apply time instead — you pick the layers, eXLib fills them in, and the code never changes.
- Its home. Saved into the library it becomes searchable, taggable, portable between projects, and shareable as a single file.
The six entries below are the same idea from six angles.
The six
| Job | Entry |
|---|---|
| Get one expression onto one property, correctly | Write & Apply an Expression |
| Turn it into something with knobs | Rig an Expression with Controls |
| Use it again — tomorrow, or in another project | Reuse an Expression Anywhere |
| Drive twenty properties, not one | Apply to Many Properties at Once |
| Reach into another composition | Work Across Compositions |
| Find out why a rig stopped working | Troubleshoot a Broken Rig |
Read Write & Apply an Expression first even if you know the panel. Everything after it assumes the audition-then-apply loop it describes.