Open a collection’s settings and choose the **Processing** tab to see and toggle the steps. Turning a step on (or off) stamps the collection for reprocessing; the new columns and artifacts appear when the run finishes.

The Processing tab — core steps always run; the optional steps below are per-collection toggles.

## Core steps (always run)

**Scale → Pyramid → Atlas** build the visuals the viewer renders:

- **Scale** resizes each source image and records its dimensions.
- **Pyramid** generates deep-zoom tiles so you can zoom into an image at full resolution.
- **Atlas** packs thumbnails into large texture sheets so thousands of tiles render on the GPU at once.

These run for every collection — they’re what makes the grid and zoom work.

## Optional analysis

| Step | What it produces | Turn it on when… |
| --- | --- | --- |
| **Parquet metadata** | A columnar copy of the metadata, queried in-browser with DuckDB. | Almost always — it’s what makes filtering and sorting fast on large collections. |
| **KTX2 compressed textures** | GPU-compressed atlas tiles. | You want lower VRAM use and faster load. Needs `toktx` on the server. |
| **CLIP embeddings** | A 512-dim visual embedding per image. | You want visual-similarity and semantic (“a red car”) search. |
| **UMAP** | A 2D embedding (the `MAPPER X` / `MAPPER Y` columns). | You want a meaningful **Scatter** layout that clusters similar images. |
| **TDA** | Topological cluster + density columns. | You want cluster/outlier structure to colour or filter by. |
| **Visual features** | Brightness, contrast, saturation, blur score, dominant colour, scene change. | You want to filter or heatmap by image properties without writing metadata. |
| **GEMMA** | Text embeddings of metadata text. | You want semantic search over text fields. |

Most collections want **Parquet** on; the rest depend on what analysis you need. CLIP and UMAP together give you the similarity search plus the clustered scatter layout shown in [Viewing collections](/content/docs/viewing-collections/index.html).

## Reprocessing

Changing toggles, adding images, or replacing metadata all require a reprocess. The pipeline is incremental — it skips work whose results are already current:

- **Adding images** reprocesses only the new images, not the whole collection.
- **Metadata-only changes** re-run just the metadata-dependent steps (Parquet, layout, TDA); image tiers stay cached.
- **Per-image edits** (replace / rotate / flip) rebuild just those slots’ tiles.

See [Data tab](/content/docs/data-tab/index.html) for the content-change workflows and [Uploading collections](/content/docs/uploading-collections/index.html) for what each pipeline step does at import time. Operational controls — cancel a run, reprocess from scratch, roll back a version — live on the **Actions** and **Versions** tabs ( [Collection settings](/content/docs/collection-settings/index.html)).