changes to expressions in After Effects CC 2015 (13.5)
The interactive performance improvements in After Effects CC 2015 (13.5) include significant enhancements to how expressions are evaluated. Expressions are now evaluated on the render thread, meaning the user interface will no longer slow down while an expression is calculating; cache markings affected by an expression, for example, are updated on-the-fly instead of waiting for the expression to complete. Also, some expression-heavy compositions may render faster due to expanded use of the internal expression cache, especially when one expression is dependent on the results of other expressions.
What will be more visible as you work is that when an expression fails to evaluate:
- Expression errors appear in a warning banner at the bottom of the Composition and Layer panels instead of in a dialog box.
- The expression is not automatically disabled and will continue to evaluate.
The warning banner will display as long as the expression fails to evaluate; that is, until the expression is either fixed or manually disabled.
This means that when you have multiple expressions that fail, you no longer need to click through all of the error dialog boxes that appear. Also, when you fix the cause of an expression’s failure, you no longer have to click to re-enable it. That includes if you simply undo the change that caused the expression to fail.
We know that many After Effects users utilize expressions heavily and that in some of their projects, changing a single property or deleting a single layer could cause hundreds of related expressions to fail. We hope these changes provide some relief to the fingers of expression-heavy users.
Here’s an example of what the expression error warning banner looks like:
On the right side of the expression error warning banner are control buttons:
- The Left or Right arrow buttons display the previous or next expression error when multiple expressions fail to evaluate.
- The Reveal Expression (magnifying glass) button will expose the property with the failing expression in the Timeline panel. If the expression is in a different composition, that composition will open.
- The Expand/Collapse Warning (up/down arrows) button shows or hides the error text.
Note: The expression error text is one line only, and is clipped to the width of the Composition panel. To see the full expression error text in the old-style dialog box, click on the yellow error triangle icon next to the expression in the Timeline panel.
You can hide the entire warning banner if you find it distracting. Choose After Effects CC (Mac OS) or Edit (Windows) > Preferences > General and disable Show Warning Banner When Project Contains Expressions Errors. But remember that when this option is disabled, the warning banner remains hidden even when new expression errors occur. Re-enable this option to view expression errors.
Let us know what you think about the changes to expression evaluation on the After Effects forum.
Also worth mentioning in this context is a feature that is not new, but has existed in After Effects for many versions: the Reveal Expression Errors command, available the in the context menu when you right-click on a layer, will expose properties of the selected layers that have expressions that fail to evaluate.