Materials

The Materials section

In DESIGN, pick an editing mode on the rail — Roads, Blocks, Lots or Massing — and open the Materials section in the column. Its body is a carousel showing three material tiles at a time, with flat ‹ and › steppers on either side. The arrows are hidden, not greyed, at the ends of the list.

One tile is one library category. A tile with nothing assigned shows the flat colour of the material the geometry is really rendering with right now — the mode's default datablock, named default_roads, default_lots and so on, findable in the Outliner under exactly that name. Hover it and the tooltip reads “Pick a Asphalt material (currently default_roads)”. Once assigned, the tile shows the material's preview image and the tooltip names it.

Each mode dresses a fixed set of categories, and the carousel lists only the ones your library actually contains. A category the library has never seen is filtered out, so a tile never opens onto an empty grid.

Roads is the one mode whose set follows its sub-mode, so the carousel changes under you when you switch between Road and Sidewalk. Its page position is remembered per sub-mode rather than per mode, so switching back does not land you somewhere in the middle of a different list.

On a library that stocks none of a mode's categories the section shows a single muted line, “No material categories for this mode.” Dress the city with a theme first — see Themes and What a theme contains.

Assigning by category

Click a tile and the asset browser opens over the 3D viewport with its tree locked to that one category. The panel title says which: PICK A ASPHALT MATERIAL for a single locked category, or PICK A MATERIAL — CURBS, SIDEWALKS when several are on offer (the title lists them alphabetically, whatever order the mode dresses them in). The lock is deliberate — clicking Asphalt offers asphalt and nothing else.

1. Click the tile for the category you want to change.
2. Click a card in the grid. It outlines in accent colour and the footer line names it — “Asphalt 04 · Asphalt · Library”. Clicking the same card again deselects it.
3. Press Assign. The browser closes.

Two things happen at once. The datablocks already on screen for that category are rebuilt in place from the picked material's folder, so the dressed viewport re-skins immediately without a re-dress. And the category is pinned to that material, so every future dress resolves it first.

Open Library, at the left of the category tabs, is the same trip without choosing a tile first: it opens the browser on the whole set of categories the mode dresses, and whatever you pick lands on the card for the category it came from. Pick something outside the mode's set and a card for it is added to the end of the carousel, which then pages to it.

A finished theme fills these cards for you: its materials are assigned to their categories as they download. The theme wins the categories it covers, and later manual picks override it until the next theme arrives. What a re-dress keeps and what it rebuilds is set out in What survives a re-dress.

Generating a new material

With nothing selected in the picker, the footer offers Generate with AI in place of Assign. It opens the Generate with AI popup on the Material tab.

1. Open the picker from a tile or from Open Library, and click no cards.
2. Press Generate with AI.
3. Describe the material in the box. The placeholder shows the shape of a usable prompt: “e.g. wet cobblestone with moss in the cracks, PBR”. A plain generate refuses an empty box.
4. Optionally attach reference images, or an existing library asset, as tiles under the box.
5. Press Generate. The popup closes and the job is tracked in the composer thread and in Cloud Activity.

If the cloud finds close matches already in your library, a Library Suggestions dialog appears before anything is generated: “The library already has close matches”, each with a preview, its name, its category and a Use this button, plus None of these — generate new at the bottom. Closing the dialog without deciding leaves the job waiting on the cloud.

When the job completes the material is saved into your local library and the log reads “Saved N generated assets … to the local library”. It is not put on a card for you — that auto-assignment happens only for a whole theme. Reopen the picker and press Assign to use it. The single-asset lane in full is in Single materials & props.

Regenerating one in the scene

Regenerating re-renders an existing material from its own cloud identity. The result lands as a new seed beside the old one rather than replacing it; a card holding more than one seed grows a more · N chip at the bottom right of its preview, and clicking it shows every version.

There are two ways in, and they differ in how many you can do at once.

From the picker. Select exactly one card and the footer swaps Generate with AI for Regenerate. It opens the same popup, with the source material shown as an image tile under the box and the button relabelled Regenerate.

From the composer. On the Theme tab, press the first icon on the composer strip — the one whose tooltip reads “Generation options — what to generate, asset sourcing, editing modes”, not the paperclip beside it — to open Generation Mode, and under Editing mode choose Edit material. Choosing the active mode again leaves it and returns to Generate.

1. With Edit material active, a pick icon appears on the composer strip, tooltip “Pick the materials to edit (active in the scene)”. Press it.
2. The browser opens headed SCENE MATERIALS — PICK TO EDIT. Click every material you want re-rolled.
3. Press Done. The picked targets appear as tiles under the composer box.
4. Type an adjustment, or leave the box empty for a fresh variation of the original, and send.

Every picked target gets its own regenerate job, so three targets is three jobs and three charges. Progress and failures are read in Jobs, progress & errors.

What it costs

The Generate with AI popup prints an estimate at the bottom left, Est. cost: followed by credits and minutes. These are hard-coded figures measured from completed jobs, not a live quote from the server.

A material is a small fraction of a theme, so you can re-roll one road surface many times for the price of a single theme run. Re-rolling the guide images during a theme job is not cheap that way: each re-roll is its own job with its own charge.

Custom materials

Materials from your own folders — the custom assets directory and the extra asset paths set in Preferences — appear in the picker beside downloaded ones, and the footer info line labels them Custom rather than Library. You can assign them to a category exactly like any other material.

What you cannot do is send them back through the cloud. A custom material has no cloud identity, so the whole generation side refuses it.

• —Regenerate does nothing. The refusal — “has no cloud identity (local/custom asset) — only cloud-downloaded assets can be regenerated” — is written to the system console, not to the panel.
• —Edit material skips custom picks and logs “has no cloud identity (local/custom asset) — skipped” for each. If every target you picked was custom, the submission is cancelled with “None of the picked targets are cloud assets.”
• —Add to group answers “This is a local asset - it has no cloud identity.” on the picker's info line.
• —The star is not drawn on a custom card at all. Starring is keyed on the cloud asset id, so there would be nothing to star.

Where custom assets come from and how to point the addon at them is in Your own assets.

One cloud action is not a regeneration and is worth keeping apart: Generate PBR. It appears when a downloaded material's own config asked for PBR maps and none are on disk. It sends no prompt and re-decides nothing about the material — it builds the missing maps onto the same seed. See Filling the gaps.