Surface details

Where Surface details lives

Surface details is the last section of the Design column, under Parameters, Materials and Props. It appears in every element mode — Roads, Blocks, Lots and Massing — and it starts collapsed, so click its header to open it. Design itself is locked until you are signed in and a city exists.

The section holds scattering systems. One system is one card: a set of assets, a shape you draw in the 3D viewport, and the numbers that decide how the assets are spread over that shape. The card title reads Imperfections scatter 1, 2 and so on until you rename it.

Creating a system

The + centred under the section's cards opens a menu titled Place props… with four entries. The one you pick fixes what kind of shape the system scatters over, and it cannot be changed afterwards — switching a system from a path to a surface halfway through would strand the shapes it had already drawn.

• —On Edge — an open polyline. Assets land along it at a fixed spacing.
• —On Surface · Distribute — a closed polygon. Assets are scattered at random inside it.
• —On Surface · Packed — the same closed polygon. Packing is not wired yet, so this behaves exactly like Distribute today.
• —On Points — you click the points yourself and one asset lands on each.

The new card carries a small icon in its top-right corner showing what it is: a surface, an edge path, or hand-placed points. The card is backed by a Blender collection named Scatter_<mode>_<id> under iCity 2 > Assets, which is where the shapes you draw and their instances go.

Adding imperfection assets

A system with no assets scatters placeholder cubes, so fill it before you draw. Open the card's objects panel and press the + inside it. The library browser opens on the imperfections view, in multi-select: tick several assets and press Assign to add them all at once.

1. Open a system card and expand objects.
2. Press +. The browser opens showing imperfection assets only.
3. Select one or more assets and press Assign — it reads Assign 3 when three are ticked. Each one is imported immediately and gets its own copy of the system's numbers.

Imperfections are not a separate library folder. They are the materials and props whose category is imperfections, gathered into one view. That is why an image-based asset works here: an image comes in as a decal plane, a model comes in as an object.

Each object row has its own eye and camera toggles and its own copy of the sliders, so one asset in a system can be denser than the next. See Browsing, starring and groups for the browser itself.

Drawing the area

The bottom row of the card is Draw (or Place points on an On Points system), then the eye, the camera and the × that deletes the system. Pressing Draw arms a draw tool aimed at this system; pressing it again disarms it. While it is armed you click in the 3D viewport.

1. Press Draw. The button highlights while the system has assets but nothing drawn yet.
2. Click in the 3D viewport to lay down points. The status bar counts them — “Draw Surface: 2 of 3 Points” — and shows ENTER Confirm, ESC Cancel, LMB Add Point.
3. Press Enter to confirm. A surface needs at least three points, a path at least two, and an On Points system at least one.
4. The assets scatter over the shape at once and the status bar reports how many instance points it made.

Esc or a right-click cancels the stroke and nothing is built. The tool stays armed after a confirmed stroke, so you can draw several areas into the same system without going back to the card.

Density, seed and the other numbers

The options panel only appears once the system has both assets and a drawn shape — before that there is nothing for the numbers to act on. Left closed, its header carries the everyday sliders inline, abbreviated to fit: Dns, Mrg, seed on a surface system.

Which sliders you get depends on the kind of system. A surface system gets Density and Seed; an edge system gets Spacing, Offset and Depth; an On Points system gets none, because you placed the points yourself and there is no distribution left to tune.

Seed does what its name says and nothing more. The same seed over the same shape at the same density gives you the same arrangement every time; change the seed and you get a different arrangement of about the same number of instances. Two assets in one system never land on identical points even at the same seed — each is offset by its position in the list, so they interleave.

The sliders on the card are global: moving one sets every object in the system. The sliders on an individual object row set just that object. Either way the shapes re-scatter as you drag, so you see the result while you are still holding the slider.

If a drawn area is small and the density low, the arithmetic can round down to nothing. The card says so when it happens:

Draw Surface: 2 object(s), 0 instance point(s) (add an asset with + / raise density)

The theme's own surface details

After a dress, Surface details also lists cards the linker built for whatever you have selected. These are the theme's own imperfections — the taxonomy categories crack, litter and surface_imperfection — and they sit above your own systems, collapsed by default.

They behave differently. They have no Draw button, because they are already on the city elements the dress put them on. Their action row is Assign selected and Remove selected, which give or take those props from whatever you have selected in the viewport. Their options row carries Density and Seed only, and moving one re-bakes that card.

Individual object rows on a linker card carry no sliders on purpose: the bake is per category, so a per-asset number would have nothing to land on. The card's own options row is the control. For what a dress produces, see After a dress.

What is stored, and what is only drawn

Your scattering systems, their sliders and their asset lists are saved into the .blend as scene data, and the shapes and instances are Blender objects under iCity 2 > Assets. This is the exception rather than the rule: your city is not your .blend, it lives in the engine process — see How iCity fits into Blender.

A few controls on the card are drawn but not yet acted on. They store what you set and change nothing on screen:

• —Margin on the collapsed options header.
• —The Random X, Random Y and Random Z rotation rows with their minimum and maximum angles.
• —Snap to face and Align to face.
• —On Surface · Packed, which scatters the same way as Distribute until the packer is wired.