Building Generator

With the Spline Building Generator you draw a spline, and PolyBash builds a building along it. The generator creates outer walls, inner walls, floors, ceilings and a gable roof. Doors, windows and floor openings cut the shell, and generated frames fill each door and each window.

This page documents every section of the inspector. The page Spline Generators Overview explains the parts that both generators share, such as the build cycle, the stage system and the Info section.

How the spline becomes a building

The spline describes the centerline of the building plan, and not the outer wall itself.

The generator builds the outer wall along the corridor boundary. The inner wall follows the same boundary, offset inward by Wall Width.

A section produces nothing in these cases:

• Its Top Level is 0.
• Its two knots occupy the same position in the horizontal plane.
• Its Bottom Level is above its Top Level.

Quick start

1. Create the generator, as the section Add a generator to a scene describes.
2. Draw a spline with at least three knots.
3. Assign a material to Default Material.
4. Open the Levels section, and set Level Height.
5. Open the Per-Section Levels foldout, and raise Top Level to 2 for some sections.
6. Open the Walls & Corridor section, and set Left Offset and Right Offset.
7. To apply both values to every knot, select Reset All To Global in the Per-Knot Offsets foldout.
8. Open the Openings section, and select Add Door and Add Window.
9. Set a different Position on each of the two new cards, such as 0.2 and 0.6.
10. Open the Roof section, and set Roof Type to Gable.

Levels

This section defines the height of each level. Open the Level foldout inside the section for the two fields.

The generator stacks the levels from the local height 0 upward. Level 1 spans from 0 to Level Height, and level 2 continues above it. An override changes one level, and it shifts every level above that level.

Per-Section Levels

The foldout Per-Section Levels holds one row per section, and each row carries two values. The row labels count from 0, and the generated nodes count from Section-01.

Different values per section produce a building with parts of different heights, so a tower needs a high Top Level on only one section. Set both values to 0 to leave a section empty, so that the building receives a gap.

PolyBash resizes this list after each change of the knot count. It adds and removes entries only at the end of the list, and a new entry receives a value of 1 for both fields. After you insert or delete a knot inside the spline, verify the values that follow it.

Walls & Corridor

This section defines the wall geometry and the corridor width. Open the Wall foldout inside the section for the fields.

A Wall Width of 0 places the inner wall on the outer wall, so the wall has no thickness.

Curve Segment Length affects only curved sections. A section whose two knots both use the tangent mode Linear stays one straight segment.

Wall collider modes

The Primitives mode splits each wall into bands: one band lies below the sill of an opening, and one band lies above the head, so a door or a window stays passable.

Neighboring wall segments merge into one box while the error stays below Wall Collider Tolerance. As a result, a straight wall needs few boxes, and a tight curve keeps more. A value of 0 produces one box per wall segment. The inner walls never receive a collider.

Per-Knot Offsets

The foldout Per-Knot Offsets holds the corridor half-widths of each knot, and the build uses only these values. PolyBash adds and removes entries only at the end of the list, and a new entry receives the values of Left Offset and Right Offset. After you insert or delete a knot inside the spline, verify the values that follow it. Reset All To Global copies Left Offset and Right Offset to every knot. You can also drag the cyan handles in the Scene view to edit the values. Hold Shift to move both sides at the same time.

Caps & Floors

This section defines the horizontal surfaces. Open the Cap foldout inside the section for the fields.

The floor of a level sits at the bottom of that level. The ceiling sits below the top of the level, at the distance of Ceiling Offset From Top.

Cap Collider Mode offers None and Mesh. The Mesh mode reuses the rendered surface, so the holes of the floor openings stay open in the collider. That collider is concave, which means that it works only for static objects.

For a building without a roof, or for a roof terrace, select Generate Top Floor.

Openings

This stage cuts the doors, the windows and the floor openings. Every later stage reads those cuts, so the walls, the floors and the frames stay consistent.

Doors & Windows

The foldout Doors & Windows holds one card per opening. Select Add Door or Add Window below the cards to add one. The title of a card shows an automatic name, such as "Window 2". To replace that name, enter a text in the field beside the title. The Remove button in the header of a card deletes that opening.

A new door uses the width 0.9, the height 2.1 and the sill height 0. A new window uses the width 1, the height 1.2, the sill height 0.9, the count 1 and the spacing 1. Both use Insert Colliders = Boxes.

With Boxes, a door frame receives three box colliders and a window frame receives four, one per bar. The leaf or the sash receives one more box as a child of that part, so the box follows the part when the part opens. An opening that wraps a corner, or that sits on a curved section, splits each bar into one box per straight span. The section Frame Inserts describes the inserts themselves.

A window that uses a Count above 1 creates a row of copies along the perimeter. Every copy uses the width, the height and the sill height of the card. The gap between two adjacent copies is Spacing (m), so the distance between two centers is the sum of Width (m) and Spacing (m). The whole row stays centered on Position.

Position runs along the closed perimeter of the building. Position 0 lies at the corner between the left wall and the wall that closes the start of the spline. The value first crosses that start wall and grows along the right side. It then crosses the wall at the end of the spline, and returns along the left side.

The generator clamps each opening, so that it stays inside its level:

• A door starts at the floor. Its head stays below the top of the level.
• A window sill stays at 0.05 meters or above.
• The head of a window stays below the top of the level, so a high sill reduces the height.
• The width stays below the length of the perimeter.
• The row of copies of a window stays below the length of the perimeter. The generator reduces Count when the row does not fit.

An opening appears only when its Level lies between Bottom Level and Top Level of its section. Each copy of a window follows that rule with the section that holds the copy.

Floor Openings

The foldout Floor Openings holds one card per hole in a floor, and a floor opening produces a stairwell or a light well. Select Add Floor Opening to add one. The title of a card shows an automatic name, such as "Opening 1". To replace that name, enter a text in the field beside the title. The Remove button in the header of a card deletes that opening.

A new floor opening uses the level 2, the width 1.5 and the depth 2.5.

A hole at level N cuts the floor of level N and the ceiling of level N-1. The generator also adds the vertical surfaces between both edges, so the hole shows a closed shaft.

Scene handles

The toggle Opening Handles in the Scene Gizmos section controls the handles of this stage.

• A door or a window shows a vertical line and two handles. Drag the sphere at the center along the wall to change Position. Drag the cube at the upper-right corner, as seen from outside the building, to change Width (m) and Height (m). The width grows on both sides, so the center of the opening stays in place.
• A window also shows a cube at the bottom center, and a drag of that cube up or down changes Sill Height (m).
• A window that uses a Count above 1 shows one vertical line and one set of handles per copy. The handles of every copy edit the same card. Drag the center sphere of any copy to move the whole row, because the row stays centered on Position. The label reports the number of copies.
• A floor opening shows its rectangle and a handle. Drag the handle in the plane of the floor to change Center (X, Z).

Roof

This stage builds a gable roof, and it produces nothing while Roof Type is None.

The ridge follows the spline, at Roof Height above the top of the run. Both slopes reach the corridor boundary, so the values in Per-Knot Offsets control the width of the roof. An asymmetric corridor produces two slopes of different angles.

The generator builds one roof per run of equal top level. A run that stands beside a taller run receives a clipped roof, so that the roof stops at the taller wall.

In both collider modes, each end of a run that does not touch a taller run receives one more collider for the gable triangle.

Frame Inserts

This stage fills each door cut and each window cut with a generated frame, and it produces nothing while the Openings stage adds no cuts.

A window frame has four bars: two jambs, one head bar and one sill bar. A door frame has three bars, because the leaf reaches the floor. The generator clamps the border of each frame, so that the opening stays open. Every material of this stage falls back to Default Material.

Insert cards

The section holds two lists, Window Inserts and Door Inserts, and each list holds one card per frame style. Select Add Window Insert or Add Door Insert below a list to add a card. A new stage starts with one window card and one door card.

The title of a card shows an automatic name, such as "Window Insert 2". To replace that name, enter a text in the field beside the title. Duplicate copies the card, including its opening selection, and Remove deletes it.

Applies To selects the openings that receive the card:

The first card of a list uses All Openings. Each further card starts with Selected Openings and an empty selection, because a second card with All Openings would never receive an opening. When several cards match one opening, the first card in the list wins. An opening that no card matches stays an open cut. A card without a selected opening builds nothing, and the card reports that state below the list.

A card selects an opening through a stable id, so the selection survives a reorder, a rename and a deletion of other openings.

The colliders of an insert come from the Insert Colliders field of its opening, which the section Doors & Windows describes.

Window cards

A nonzero Frame Depth stays centered on the middle plane of the wall. As a result, a deeper frame protrudes on both faces, and a shallower frame recesses on both faces.

Lattice Material and the lattice fields below appear only while Add Lattice is on. The lattice is double-sided, so its total depth is twice the value of Rail Height.

Window pane pivot

These three fields move the local origin of the glass, and the glass itself stays in place.

The generator groups the glass and the lattice under a node whose name ends with _Sash, and it places that node at the pivot. The local axes of that node follow its wall: +Z points out of the building, +Y points up, and +X runs along the wall. Rotate that node around one local axis to open the window, and the window opens the same way on every wall. For a hinge on one edge, select Min or Max for Pane Pivot X.

The two fields below rotate the sash at build time, so a building generates with open windows.

A positive angle follows the rotation direction of Unity around the selected axis. Around Y, a sash with Pane Pivot X = Min swings out of the building, and a sash with Max swings into the building. Around X, a sash with Pane Pivot Y = Min tilts its top edge out of the building. Use a negative angle for the opposite direction.

Door cards

The leaf is a stile-and-rail panel door. The generator solves it per opening, so the fields below describe the pattern and not the size.

When Panel Depth or Chamfer is outside its limits, the generator skips the leaf and writes a warning to the Console window.

When light passes through the thin areas of the panels, raise Core Thickness.

Door leaf pivot

The pivot of the leaf behaves like the pivot of the sash, which the section Window pane pivot describes. The leaf object uses the same local axes as the sash node. As a result, a rotation around the local Y axis opens the door the same way on every wall. The default Min for Leaf Pivot X places the hinge on the left edge.

The two fields below rotate the leaf at build time, so a building generates with open doors.

The sign of the angle follows the same rules as Pane Open Angle: around Y, a leaf with Leaf Pivot X = Min swings out of the building, and a leaf with Max swings into the building. The knob and the colliders are children of the leaf, so they follow the rotation.

Door knob

The four fields below Knob Prefab appear only after you assign a prefab. The knob needs the leaf, so Include Leaf must stay on.

The generator clamps Knob X to the width of the leaf. With the default values, the knob sits near the hinge, because Knob X and Leaf Pivot X both use the left edge. For a normal door, set Knob X near the width of the leaf, as the sample scene does.

Author the prefab with the knob along the +Z axis, from its mount point at the origin. The generator orients each instance with +Z toward the outside of the building.

Double inserts

Double Sash on a window card and Double Leaf on a door card build two moving parts side by side inside one frame. Each part is half of the reveal wide, and no frame bar separates the parts. The frame itself stays the same, and the generator solves the lattice per sash, so each sash receives its own lattice.

The left part, as seen from outside the building, follows the pivot, the open angle and the knob fields of the card. The right part mirrors the left part across the center of the opening:

• The pivot X swaps Min and Max. As a result, a hinge on the left edge of the left part becomes a hinge on the right edge of the right part.
• The open rotation around Y or Z changes sign, so the two parts open in opposite directions. A rotation around X stays the same on both parts.
• The knob of the right leaf sits at the mirrored spot. The instance receives a negative scale on X, so a handed knob stays correct.

The generated objects of a double insert carry _Left or _Right after the insert name, for example DoorInsert3_Left_Leaf and WindowInsert3_Right_Sash. A single insert has no suffix.

Materials

Each part carries its own material field, and an empty field falls back to another material.

At each end of a roof run, the inner triangle above the wall uses Inner Wall Material → Default Material, not the roof materials.

Generated output

The generator writes its result into child objects, and each mesh object and each node carries the marker component Generated Output. The wall boxes, the insert colliders and the knob instances carry no marker, but each one is a child of a marked object.

<generator GameObject>
├── Section-01
│   └── Level-01
│       ├── Floor
│       ├── OuterWalls
│       ├── InnerWalls
│       ├── Ceiling
│       └── TopCap
├── Roof
│   └── Section-01
│       ├── RoofTop
│       ├── RoofBottom
│       ├── RoofEaves
│       ├── RoofEndCaps
│       ├── RoofEndCapsInner
│       ├── RoofEndStart
│       └── RoofEndEnd
├── WindowInserts
│   └── Section-01
│       ├── WindowInsert0
│       │   └── Collider-0 … Collider-3
│       └── WindowInsert0_Sash
│           ├── WindowInsert0_Pane
│           ├── WindowInsert0_PaneInside
│           ├── WindowInsert0_Lattice
│           └── Collider-0
└── DoorInserts
    └── Section-01
        ├── DoorInsert1
        │   └── Collider-0 … Collider-2
        └── DoorInsert1_Leaf
            ├── DoorInsert1_Knob
            ├── DoorInsert1_KnobMirror
            └── Collider-0

Notes on the names:

• The number of an insert is the position of its opening card in the Doors & Windows list, counted from 0. Doors and windows share that list, so the count includes both types. The number in the card title differs, so the card "Window 1" at the top of the list produces WindowInsert0.
• A window that uses a Count above 1 adds the index of the copy after an underscore, such as WindowInsert2_0 and WindowInsert2_1.
• A box collider appears as a child of OuterWalls, with the name WallBox-0 and the following numbers.
• A roof collider appears as a child of the section node of the roof, with the name RoofCollider-0 and the following numbers.
• The node TopCap exists only while Generate Top Floor is on.
• The knob objects exist only while Knob Prefab holds a prefab, and the object DoorInsert1_KnobMirror exists only while Knob Mirror is on.
• An insert collider appears as a child of the frame, of the sash or of the leaf, with the name Collider-0 and the following numbers. The generator adds these objects only while Insert Colliders of the opening is Boxes.

Troubleshooting