working on getting dark sequence rendered

.specstory/history/2025-11-01_15-48Z-png-rendering-error-troubleshooting.md

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+<!-- Generated by SpecStory -->
+
+<!-- cursor Session 4aeb7f9e-851f-4b2a-ae52-01c07b68e74f (2025-11-01 15:48Z) -->
+
+# PNG rendering error troubleshooting (2025-11-01 15:48Z)
+
+_**User (2025-11-01 15:48Z)**_
+
+why is this happening to render
+
+
+
+libpng error: IDAT: CRC error
+
+ImageInput::read_image() failed: PNG read error: IDAT: CRC error
+
+PNG library error
+
+IMB_load_image_from_memory: unknown file-format (R:\Creative\artsy\maya\2025-02 BondingArtifact\Renders\3_background\2025-10-26\3_background_dark\3_background_dark_5489.png)
+
+---
+
+_**Assistant (default)**_
+
+
+
+---
+
+
+Reviewing the open file to understand the render configuration and identify why PNGs are being corrupted.
+
+
+---
+
+Tool use: **read_file**
+
+Read file: c:\Program Files\Blender Foundation\Flamenco 3.7\scripts\TalkingHeads cycles_optix_gpu_NOBAT.js
+
+---
+
+Tool use: **codebase_search**
+
+<details>
+                <summary>Searched codebase "How are PNG images saved or written during rendering?" • **3** results</summary>
+            
+| File | Lines |
+|------|-------|
+| `.gitignore` | L134 |
+| `.gitattributes` | L47 |
+| `misc/checklist.txt` | L52 |
+
+</details>
+
+---
+
+
+
+---
+
+Checking the render configuration and the corrupt file path for clues.
+
+
+---
+
+Tool use: **codebase_search**
+
+<details>
+                <summary>Searched codebase "Where are render output files written or saved?" • **10** results</summary>
+            
+| File | Lines |
+|------|-------|
+| `.gitignore` | L134 |
+| `assets/Objects/gems/tx/BlackOnyx/Designer/BlackOnyx.sbs` | L3573-3642 |
+| `misc/checklist.txt` | L52 |
+| `misc/metadata.bat` | L23 |
+| `misc/filenames.bat` | L1 |
+| `.cursorindexingignore` | L3 |
+| `.gitattributes` | L47 |
+| `assets/Objects/gems/tx/BlackOnyx/Designer/BlackOnyx.sbs` | L1475-1533 |
+| `misc/BRANDING.txt` | L2 |
+| `assets/Objects/gems/tx/BlackOnyx/Designer/BlackOnyx.sbs` | L1976-2034 |
+
+</details>
+
+---
+
+Tool use: **grep**
+
+<details>
+<summary>Grep for "3_background" • 0 matches</summary>
+
+Output mode: content
+
+
+_No matches found_
+
+</details>
+
+---
+
+
+
+---
+
+This PNG CRC error indicates the file was corrupted during render. The path `R:\...` suggests a network drive, which is a common source.
+
+Common causes:
+- Network storage issues: timeouts, interruptions, or bad connections corrupt writes
+- Concurrent access: another process (comp, preview, antivirus) reading while a worker writes
+- Incomplete writes: file read before the write finishes
+- Antivirus/backup: scanning or copying files while they’re being written
+
+Checking the render script for timing or synchronization issues:
+
+
+---
+
+Tool use: **read_file**
+
+Read file: c:\Program Files\Blender Foundation\Flamenco 3.7\scripts\TalkingHeads cycles_optix_gpu_NOBAT.js
+
+---
+
+
+
+---
+
+## Solutions to fix this:
+
+### **Immediate fixes:**
+
+1. **Check if the file is actually corrupted**
+   - Verify frame `5489` on the R: drive
+   - If corrupted, re-render just that frame
+
+2. **Render to local storage first, then copy**
+   - Change the render output to a local drive (C: or D:)
+   - After rendering completes, copy to the network drive
+   - Reduces corruption risk from network interruptions
+
+3. **Increase chunk_size**
+   - In your Flamenco job settings, increase `chunk_size` (currently defaults to 1)
+   - Fewer concurrent writes = less contention
+
+4. **Temporarily disable antivirus/backup scanning**
+   - Exclude the render output folder from real-time scanning
+   - Network drives are often scanned aggressively
+
+### **Network storage specific:**
+
+5. **Check network drive health**
+   - Test the R: drive connection stability
+   - Run `chkdsk R: /f` if it's accessible
+   - Check for network timeouts or packet loss
+
+6. **Add file write delay/sync**
+   - If possible, configure Blender to flush writes completely before finishing
+   - Use `--python-expr` to add a small delay after rendering completes
+
+### **For the current corrupted frame:**
+
+The file `3_background_dark_5489.png` is corrupted. Either:
+- Re-render frame 5489 specifically, or
+- Skip it and continue (if it's not critical)
+
+Should I help modify the Flamenco script to render to a local directory first, or focus on diagnosing the network storage issue?
+
+---
+