A render finishes, you scrub through the sequence, and there are holes. A few frames are missing entirely, a couple are half-written or weirdly tiny
A render finishes, you scrub through the sequence, and there are holes. A few frames are missing entirely, a couple are half-written or weirdly tiny on disk, and one is pure black. The slow, painful response is to re-render the whole thing. The response that gets you home on time is to find exactly which frames are broken and re-render only those. After enough sequences I have a quick routine for this, and it turns an hour of redoing finished work into a few minutes of patching.
How I find the broken frames fast
| Method | What it catches | Effort |
|---|---|---|
| Sort the folder by name, scan for gaps | Missing frames in the sequence | Seconds |
| Sort by file size | Half-written or corrupt frames that are too small | Seconds |
| A frame-check script | Lists exactly which frame numbers are absent or undersized | A little setup, big payoff on long jobs |
| Load the sequence in your comp app | Black or visibly broken frames you can see | Low |
The file-size trick that saves me every time
Missing frames are easy to spot, since the numbering skips. The sneaky ones are frames that exist but are broken, half-written after a crash, or rendered black, because they still show up in the folder and look fine in a list. Sorting the folder by file size flushes them out, since a corrupt or empty frame is almost always much smaller than a proper one. Once I have the list of bad frame numbers, I render just that range, and because the rest of the sequence is intact, it splices straight back in.
Make patching possible in the first place
All of this only works because I render to an image sequence rather than a single movie file, which keeps every good frame independent and patchable. If you have been rendering to one big file and losing everything on a failure, switching to a sequence is the change that makes surgical re-rendering possible at all. The habit ties directly into surviving crashes, which I cover in the render crash troubleshooting guide. Render farms help here too, since most retry a failed frame automatically and hand you a complete sequence, removing the manual hunt entirely.
FAQ
How do I find which frames failed in a render sequence?
Sort the output folder by name to spot gaps where frame numbers are missing, then sort by file size to catch frames that exist but are corrupt or half-written, since those are usually much smaller than good frames. A short frame-check script can list the exact missing or undersized frame numbers automatically, which saves time on long sequences.
Can I re-render only the broken frames instead of the whole sequence?
Yes, as long as you rendered to an image sequence rather than a single movie file. Identify the broken frame numbers, render just that range, and they splice back into the intact sequence. This turns a full re-render into a few minutes of patching. Rendering to a sequence is what makes this possible.
See more: Driver Crashes During GPU Render: How I Stopped Losing Hours
Image source: BlenderNation
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