What happens
An error never breaks the render. The property keeps the value it had before the expression, the expression box turns red, and the message shows underneath it with the line and column, e.g. Line 2, column 5: unknown name "wigle" (single-line expressions say just Column N).
The box shows the compile error now, or else the last error a render hit while evaluating it.
Common messages
| Message | What to do |
|---|---|
unknown name "…" | A typo, or a name Brio doesn't have. |
"for" isn't supported in Brio expressions (no loops or functions — the last line's value is the result) | Rewrite without loops or functions. |
++ and -- aren't supported — write x = x + 1 | |
no layer named "…" / no layer N | Check thisComp.layer(…). |
effect "…" has no parameter "…" | Check the effect's and parameter's names. |
a property has no "…" (try .value, .valueAtTime(t) or .numKeys) | |
unknown loop type "…" | Use "cycle", "pingpong", "offset" or "continue". |
…() isn't available yet | That AE function isn't in Brio. |
wiggle() needs a numeric property | |
this string is never closed / this comment is never closed (*/) | |
the expression is empty | |
this expression is longer than 64 KB |
Loops between expressions
If expression A reads B and B reads A, the read uses the pre-expression value and the modifiers involved show an error.