Generating a theme

Before you start

A theme dresses a city that already exists. It does not draw one. Both of the following have to be true before the Design module will let you send anything.

• —You are signed in. Signed out, the Theme screen reads Sign in to start designing and offers a Sign In button instead of the composer.
• —The scene holds a city. With an empty scene the composer shows Generate a city first — the theme is applied to your city (Draft module). in amber and the send button is disabled.

Switch the header toggle to DESIGN. The rail's first tab reads Theme, and it opens on a choice screen headed How should this city be dressed? with three buttons: Start with default theme, Generate theme and Append from a project. Only the middle one goes to the cloud. The other two are described in Themes.

Press Generate theme. The choice screen is replaced by the composer: a prompt box, a row of icons under it, and the conversation thread below.

Writing the prompt and attaching references

Type into the box. Enter sends the prompt; Shift+Enter starts a new line. An empty prompt is refused with Please enter a prompt first. The placeholder text reads write something to generate.

Two icons sit at the left of the row under the box. The second one attaches reference images — its tooltip reads Attach reference images (max 10). It opens a file browser filtered to .png, .jpg, .jpeg and .webp. Attached images appear as chips above the box, and the cloud shapes the guides from them, so a reference does more to steer the result than another sentence of text.

Near the send button there is also a camera icon: Screenshot a region of the viewport and attach it to this prompt. You drag a box over the 3D viewport, the shot opens big with Accept and Retake, and Accept puts it in the same tray — counting against the same ten.

Choosing where the assets come from

The first icon in that row opens Generation Mode. Its tooltip reads Generation options — what to generate, asset sourcing, editing modes. The same settings appear on the Generate with AI popup's Assets row; there is one setting behind both.

Under Assets, pick how the job sources its materials and props:

Above that row, Generate materials and Generate props are both on. Turning one off leaves that lane out of the job; the log records the change as Generation lanes: props off for the session. Below the row, Edit material and Edit prop switch the composer out of theme generation entirely and into regenerating assets you already have — leave both off for a theme.

Sending it

1. Press Enter, or the up-arrow send button at the right of the icon row.
2. The city is exported first. If the export fails — no geometry, or a collection switched off in the Outliner — nothing is submitted and the reason is reported.
3. The project is then saved for you. If no project is open, one named Untitled (N) is created and adopted first.
4. The job is created and the city files are uploaded. The thread prints Job 1a2b3c4d created — analyzing and the step ladder starts moving: Submitting, Analyzing, Guides.

While the job is alive the send button becomes a red stop square. Pressing it cancels the run on the server. The local record is closed only if the server agreed, so read the reply: if it says the pipeline did not stop, the run is still going.

Your draft city is not locked while a theme job runs. The dress arrives later as new objects in their own collection, so Draft editing and the gizmos stay available for the whole twenty minutes.

If the library already has something close

Before generating, the cloud may search its theme library for matches to your prompt. When it finds some, the job pauses and a popup titled CHOOSE A THEME opens over the viewport. Each card shows that theme's guide images, a counter reading Theme 1 / 4 with its name, and a line of detail — who made it, its quality score, how many times it has been used, how many materials and props it carries, and its category.

• —Use this theme adopts the theme shown. Nothing is generated, so nothing is spent on generation.
• —Load more appears on the last card while the cloud has further batches to show.
• —Generate new replaces that button once there are no more to load. It opens a small box for optional extra details, then ignores the library and generates a fresh theme.

The close button on this popup reads Close (decide later), and that is exactly what it does — the job waits on the cloud for your answer.

The guide review

The job makes reference images first and stops. A popup titled THEME GUIDES opens by itself over the 3D viewport with the sheets this attempt produced — a city scene, a building close-up, a road view and whatever else the pipeline sent.

This is the checkpoint the whole flow is built around. Guides are the cheap part of the run; materials, props and elements are the expensive part, and they do not start until you press Approve. Look at the images and decide here, not after the credits are gone.

Regenerate opens the Generate with AI popup on the Theme tab, banner-headed → Regenerating Theme 1a2b3c4d. What you type there is a refinement note, not a new prompt — leave it empty for a plain re-roll. Reference images attached in that popup steer the new set. Sending it ends the current job and continues the run in a child job, which is what the thread then follows.

What it costs and how long it takes

Budget roughly 220 to 275 credits and about twenty minutes for a full theme. The Generate with AI popup's Theme tab shows ~219 credits · ~18 min. That is a fixed number built into the addon — an average of ten completed runs taken in August 2026, not a quote from the server — and it runs low: theme runs measured since have come in at 272 to 274 credits. Budget for the upper end.

A one-credit analysis fee is charged for the moderation pass when the job is created, whatever the run turns out to cost. Every guide re-roll is its own job with its own moderation pass and its own credits, so a theme you re-roll twice costs more than the figures above. What credits are and where yours come from is covered in Credits & plans.

When it finishes

Materials and props that finish early are installed into your library part-way through the run, so the library grows before the job ends. At completion, four things happen without you pressing anything.

• —The generated assets are downloaded into your local library.
• —assets.json — the theme's list of materials, props and elements — is written into the project folder.
• —The Design cards pick up the theme's materials and props, and material slots are assigned by category.
• —The dressed city is imported into the iCity2 Front End collection.

The thread closes with the credits the cloud actually charged:

Job 1a2b3c4d complete

From here, changing the draft re-dresses the city with this theme — see Re-dressing after a change — and What is in your .blend after a dress describes what the collection holds.