Troubleshooting Blender Rendering Old Scene Versions Instead Of Most Recent

Identifying The Issue

When Blender renders an outdated version of a scene instead of the most recently saved one, it can be incredibly frustrating for artists and animators. To confirm that this is the underlying problem, check the render output closely to identify discrepancies between it and the current state of the scene in the 3D viewport. If elements are missing or different versions of models, materials, or textures are used, this points to Blender accessing old autosaved files instead of the most up-to-date blend file.

To investigate further, navigate to Blender’s autosave location on your system’s hard drive. Autosaves are stored in the temp folder under /blender/ BlenderFoundation/Blender/2.xx/autosave. Open the backup blend files saved here and browse the scenes within each. Compare the state of objects, materials, particle systems, and other attributes against your main blend file’s scene to pinpoint when divergence occurred. If you locate an autosaved version that matches the unexpected render output, this confirms that Blender is rendering this outdated version for some reason rather than the desired newest file state.

Clearing Bake Cache

One potential culprit for driving Blender to render old scene data is outdated information cached from baking. Blender stores calculated bake results in cache files linked to each bake object and material. If significant changes occur to models, UV maps, or textures after initial bakes, the old bake caches can persist and output mismatched textures in rendered images and animations.

To rule out this issue, select bake result nodes in the node editor one by one and use the Delete Bake button in the Inspector. This will remove each cached bake texture and force the baking process to recalculate using the current scene materials and UVs when it re-executes. In the Material tab, set texture nodes to your newer updated images again. Test by baking textures again and confirming Blender now references the newest data to output accurate, updated results.

Invalidating Compositor Cache

In addition to bake caches, Blender’s compositor stores cached previews and composite results which can also include outdated scene data. Over time compositing node trees can change substantially, especially during shot development in film pipelines. If an old cached composite is retained, it can inaccurately sample previous version scene buffers when attempting to composite the current scene state.

The solution here is to invalidate the compositor cache entirely forcing re-composites to access up-to-date passes. In the View Layer properties open the Passes panel. Uncheck Use Memory Cache For Passes to disable storage of composited previews. Then click Free Unused Memory Cache to clear all cached compositing content for the scene. With caches cleared, re-render the scene and check that the composite now correctly samples the newest available render layer passes during image processing.

Setting Scene Save Version

Blender contains configurable preferences to control how many iterations of scenes are retained when saving. The default Scene Save Versions setting only keeps the most recent save point. However, values can be increased to allow storing older revisions of blend files in case users want to access previous scene states. Features like recovering in-progress renders require storing intermediate file history.

In some cases though, higher version values can lead to unexpected behavior when accessing older content that should be overwritten by more recent saves. Reduce the save slots to the minimum needed via File -> Defaults -> Save & Load -> Scene Save Versions = 1. Now only a single file revision is retained, ensuring that re-saves completely replace old scene data with updated content. Test by changing scene attributes and re-saving several times, each rewrite should now make the previous state inaccessible limiting Blender’s ability to reference outdated revisions.

Fixing File References

When assembling complex scenes, production workflows often utilize file linking to reference content saved externally from master blend files. This includes linking asset and animation data from other team members. Over time these linked resources get updated, however Blender can fail to reload latest versions and still reference old cached copy instead.

To fix, inspect all external data blocks driving materials, objects, animations, physics etc in File -> External Data menu. Here check file paths of references and use the Reload button to explicitly fetch newest available content from each. Watch the 3D viewport to confirm that objects and materials update visually after reloading. Now rendered output will access fresh linked content rather than potentially years old cached data.

Rebuilding Viewport Render Cache

In addition to final scene renders, Blender caches viewport OpenGL previews to accelerate editing interactivity and reduce OpenGL resource usage. However, with extensive scene updates over time, these caches still reflect old vertex data, shading states etc that no longer match current assets. As layers accumulate, Blender can incorrectly sample and composite outdated viewport caches.

To rebuild the OpenGL caches using updated scene data, enable View -> Viewport Render Cache menu. Select entries occupying excessive memory usage and click Free Render Cache to remove. Then change frame in timeline to force re-cache of new content across shaders, geometry, HDRI backgrounds etc. Repeatedly clearing old caches and updating ensures viewport closely matches final output for reliable previews.

Verifying Correct Scene

While troubleshooting rendering issues, one simple slip up is animating or editing the wrong scene entirely. Multiview pipelines can contain many shots spanning hundreds of blend files. Artists often toggle between them regularly during asset integration and shot production rounds. It’s easy to mistakenly assume your current viewport corresponds directly with render output.

So explicitly double check that your intended target scene is the active one set for rendering. In the info header, inspect which exact blend file is open and switch to the correct one if incorrect. Expand the scene block in the Outliner editor to further validate objects, models, animations etc match expected content before final render. Finally, submit your verified scene to re-render again selecting the explicit scene name as output in case another file manages to get substituted incorrectly.

Re-Saving Blend File

After extensive troubleshooting and tweaking, easy next steps are simply saving the blend file before re-rendering again as a fresh output. Even if no substantial changes were manually made, rewriting the blend file can essentially flush cached data and force Blender to re-sample the scene completely from scratch.

So before rendering, go to File -> Save (or File -> Save As) to overwrite the blend file contents again from currently memory state. Click the X icon next to file path preview to purge the existing binary so full scene data gets completely rewritten anew. Finally press F12 to initiate final render again, now using the latest re-saved blend file as its data source. Often this write flush clears any hidden gremlins causing old data to persevere.