In some cases the compositor needs to be triggered by dummy renders (empty renders) in order to get the full node tree processed. This is the case for the file output node.
Blenders processing chain with the compositor can also be used for pipeline optimization tasks. Things like preparing and save assets, passes, masks in various formats to images in an folder and naming structure optimized for your pipeline.
While this in general can be done it is really wired for (new) users to come to the conclusion to make a dummy render in order to trigger the compositor. It needs active investigation by the user and when coming across this phenomenon its perceived as an bug or error.
- Button to manually trigger a full compositor tree processing.
- Making it clear that there are some nodes that require a re-render in order to get processed. (Title / Colorcoding / ToolTip…)
- A “trigger-node” that starts processing all nodes after it with options like: onAutoSave / onManualSave…