Generating Thumbnails

Generating Thumbnail Images for Models

Overview

3D Model Muncher can automatically generate preview thumbnail images for your models. However, different workflows have different levels of automation for thumbnail generation.

Automatic Thumbnail Generation

Upload Dialog (Recommended)

The Upload Files dialog includes automatic thumbnail generation:

1. Click the actions button (box icon) in the top-right corner
2. Select Upload Files
3. Drag & drop or browse for .3mf or .stl files
4. Check the box: "Generate preview images after upload" (enabled by default)
5. Click Upload & Process

The upload workflow will:

• Save files to your models directory
• Create munchie.json metadata files
• Automatically generate thumbnails for each uploaded file
• Show progress during thumbnail generation

Note: You can select destination folders, apply categories, and add tags during upload.

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Manual Thumbnail Generation

Bulk Generate Images (For Existing Models)

If you already have models without thumbnails, use the bulk generate feature:

1. Enter Selection Mode

   • Click the Select button above the grid/list view

2. Select Models

   • Manually click on model cards to select them
   • Or use the Select All icon (checkbox) to select all visible models

3. Open Bulk Edit

   • Click the Edit button after making your selection

4. Enable Generate Images

   • Scroll to the Generate Images section in the bulk edit drawer
   • Check the Generate Images checkbox to expand the section

5. Start Generation

   • Click the Generate Images button
   • The system will automatically skip models that already have thumbnails
   • Progress will be displayed: "Generating X/Y"
   • You can Cancel generation at any time

Important Notes:

• Only models without existing images will be processed
• This operation can take time for large selections
• Other bulk edits are blocked while image generation is running
• The drawer cannot be closed until generation finishes (or is cancelled)

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Why "Generate Munchies" Doesn't Create Thumbnails

The Generate Munchies action (found in Settings → File Integrity) has a different purpose:

What "Generate Munchies" Does:

• Re-scans model files (.3mf, .stl)
• Creates or regenerates *-munchie.json metadata files
• Extracts model information (dimensions, object count, etc.)
• Preserves user data (tags, notes, category)
• Verifies file integrity

What It Doesn't Do:

• Does NOT generate thumbnails - This feature came later and was only integrated into the upload dialog and bulk edit workflows
• Does not render 3D previews
• Does not create new image data

When to Use "Generate Munchies":

• After manually adding files to the models folder
• When munchie.json files are missing or corrupted
• To refresh metadata after file changes
• For batch processing of model metadata

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Alternative: "Regenerate Munchie Files" in Bulk Edit

The bulk edit drawer also has a Regenerate Munchie Files option that works similarly to the Settings action:

1. Select models → Edit
2. Check Regenerate Munchie Files
3. Click Save

This will:

• Re-parse the model files
• Regenerate metadata
• Preserve your custom notes, tags, and category
• Does NOT generate thumbnails

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Technical Details

How Thumbnail Generation Works

The thumbnail generator:

• Uses an offscreen WebGL renderer to load the 3D model
• Captures a PNG screenshot of the rendered model
• Saves the image as a base64-encoded data URL
• Stores the image in the model's userDefined.images array
• Updates the munchie.json file with the new image data

Why It's Separate

Thumbnail generation requires:

• Active 3D rendering (GPU/WebGL)
• Loading and parsing the entire model file
• Time-consuming operations for large files

This is why it's:

• Optional during upload (can be unchecked)
• Not included in metadata-only operations
• Done on-demand for existing files

Performance Considerations

• Generating thumbnails for many models takes time
• Each model must be loaded and rendered
• The operation is serialized (one at a time) to prevent GPU overload
• You can cancel long-running operations
• Already-generated thumbnails are automatically skipped

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FAQ

Why don't my manually added files have thumbnails?

Automatic scanning creates metadata but doesn't generate thumbnails. Use the bulk generate images feature or upload files through the Upload dialog.

Can I generate thumbnails for specific models only?

Yes! Use selection mode to pick exactly which models you want, then use bulk edit → Generate Images.

What if I cancel thumbnail generation?

Any thumbnails generated before cancellation are saved. Unprocessed models remain without thumbnails and can be processed later.

Do I need to regenerate thumbnails after editing models?

No. Thumbnails persist unless you delete them. If you want updated thumbnails after changing a model file, use bulk edit → Generate Images on that model.

Can I use my own thumbnail images?

Yes! In edit mode, you can upload custom images to replace or supplement generated thumbnails.