Regions

Region and Block are the same thing

A region is the area that closes between roads. It is the parcel that splits into lots and buildings, grows a park, or stays empty. The engine calls that object a block, and so does the mode list; everywhere else the interface calls it a Region. There is one object, with two names, and this is the single most confusing word in the product.

Nothing you can do makes the two diverge, so the practical answer is to read “block” as “region” wherever it appears. Here is exactly where each word shows up.

The empty state is the one place a first-time reader meets the old word with no region in sight. It reads “No blocks yet — Blocks appear when roads enclose an area — close a road loop, or draw a block by hand”, and offers two buttons, Draw Road and Draw Region. The advice is correct even though the noun is not.

The glossary carries the code's names alongside the interface's where they differ — see the glossary.

How a region appears

Regions are not drawn by default; they fall out of the road graph. Close a loop of roads and the engine traces the parcel inside it and fills it according to its type. Every parcel the engine generates owns a region partition of its own, so there is always something to click even if you never drew one.

You can also draw one by hand. Draw Region is the first tool in the Regions rail, and D arms it; pressing D again switches it back off.

1. Press Alt+3 for Regions mode, then D or the Draw Region button in the rail.
2. Click each corner in the viewport. The cursor snaps to nearby sidewalk edges and to existing outlines; the status bar counts the points and names the snap.
3. Press Enter to confirm, or click back on the first corner — the status bar changes to Close Shape when hovering it.

The second rail tool is Draw Custom Region. It draws a polygon inside what is already there: the engine re-cuts the region partition of every Buildings-typed parcel your polygon overlaps, into the intersection and the remainder, and splits each piece into buildings on its own. A polygon that covers a parcel completely becomes that parcel's whole region. A polygon that misses everything does nothing.

Your city lives in that engine process, not in your .blend — see how iCity fits into Blender and the engine.

Selecting a region

Press Alt+3, or click the Blocks tab in the left rail. The status bar caption confirms where you are: Regions (Alt 3). The rail carries three entries in this mode — Select, which is the default, Draw Region and Draw Custom Region.

With Select armed and nothing picked, the status bar offers D Draw Region, left-click Select, Shift+left-click Extend, left-drag Box Select, and A Select All. Picking runs through the addon's own gizmos, not Blender's selection — the full explanation is on selecting and editing.

Once one region is picked the row changes to left-drag Reshape, right-click Set Type, Ctrl+I Invert and Del Delete. Dragging the body of the shape does nothing: the corner squares and the edge bars own all the movement, and G only has a target once you have picked a corner.

Del asks first: “Delete this region? This is a persistent edit — a regenerate will not bring it back.” Deleting a region is a merge, not a hole: the neighbouring region grows back over the freed area, and deleting the last region in a parcel leaves it exactly as if it had never been split.

Land Use, and the chain under it

What a region contains is one setting reached two ways, and the two use different words. Right-click the region in the viewport and the floating card carries a Type row with three buttons — Buildings, None, Parks. The parameters column under the selection header carries Land Use instead: four buttons that set the same content type and, for the two building ones, the massing family with it.

Massing Type offers Flat-Roof Mid-Rise, Mixed-Use Mid-Rise and Pitched-Roof Low-Rise. The list is not fixed: the Land Use narrows it, and so does the subdivision method — Pitched-Roof Low-Rise is not offered under Footprint Map, because grid massing comes from the pattern mesh and has no rowhouse to apply. When the two disagree entirely the row says so rather than going blank: “No massing type fits this Land Use with the current Subdivision Method. Change the method below.”

Subdivision Method is how the parcel is cut into lots, listed Straight Skeleton, Offset, Recursive, Footprint Map. Footprint Map skips lots entirely — it clips a 2D footprint map to the region boundary — so it hides Setback Mode and the lot constraints and says so where they would have been. Under Lot Settings sit the setbacks, the Lot Elevation Mode (Preserve Slope, Minimum Elevation, Maximum Elevation, Average Elevation — Minimum Elevation by default) and the chosen algorithm's own numbers. Building Height sits outside Lot Settings and carries Minimum Floors and Maximum Floors.

One naming snag worth knowing before you go looking in Blender's own property editors: the right-click button reads Buildings, but the underlying property spells that value Massing. Same value, two labels — and Residential and Commercial are both that one value, told apart by the massing type they carry.

Parks, and the park panel that never shows

Set a region to Parks & Open Space and one control appears under it: a Park Type dropdown listing Random, Park 1, Park 2, Park 3 and Park 4. The four numbered entries name the engine's built-in park designs — Default_Park_01 through 04; Random picks one per parcel.

This is the dropdown whose value travels: Park Type is packed into the parameter block the addon sends to the engine and is recorded on the region's own override, and the addon's note on that record says the engine's park processor reads the region's recorded value first. It is also the reason an unrelated edit on a park region does not re-roll the park — the fan carries the design already recorded rather than stamping the city-wide default over it.

Whether trees actually appear is a dressing question, not a draft one. See props and placements.

What belongs to a region, and what belongs to a lot

A region is the parcel. A lot is one plot inside it, carrying one building. Almost every complaint of the form “I cannot find that setting” is a control being looked for on the wrong one of those two.

The delete verbs differ for the same reason. Deleting a region merges it back into its neighbour and the parcel regrows over it. Deleting a lot removes the building and leaves the lot standing, vacant. Neither survives as a hole in the city.

• —Lots — splitting, merging, loop cuts, and the Building / Green switch.
• —Massing — floors, building types, and hand-drawn footprints.

One path the status bar advertises that goes nowhere

Select a parcel in this mode and you are always selecting a region. The addon also has a block-level selection with its own card — a Split selector (Straight Skeleton, Offset, Recursive, Footprint Map), Delete Block, and Restore Block for one already deleted — and the status bar still prints Block with a right-click Split hint for it.

You cannot get to it. The two rail toggles that chose between selecting blocks and selecting regions were taken off the rail, and the selection kind is pinned to Regions, so a click in this mode can only ever return a region. The Block row in the status bar is a hint for a state this build cannot enter.